THERMAL DEPOSITION METHODS FOR ENHANCEMENT OF

VEHICLE WHEELS

BACKGROUND OF THE INVENTION The invention relates in general to vehicle wheels and in particular to a method for forming a metal surface layer on a portion of a wheel surface.

Vehicle wheels include an annular wheel rim which is adapted to carry a pneumatic tire. The wheel rim includes an outboard tire bead retaining flange which extends radially outward from the outboard end of the wheel rim to retain the tire upon the wheel. An outboard tire bead seat is formed adjacent to the outboard tire bead retaining flange. The outboard tire bead seat is adapted to carry the outboard tire bead. The outboard tire bead seat is connected by a radial drop well wall to a recessed annular drop well. The drop well facilitates mounting a tire upon the wheel. An annular leg portion connects the drop well to an inboard tire bead seat, which is adapted to carry the inboard tire bead. The inboard end of the wheel rim is formed as an inboard tire bead retaining flange which extends radially outward from the wheel rim to retain the tire upon the wheel.

A circular wheel disc is typically formed across an end of the wheel rim. .Alternatively, the wheel disc can be recessed within the wheel rim. The wheel disc includes a wheel hub having a central pilot hole and a plurality of wheel lug holes formed therethrough for mounting the wheel upon a vehicle. The outboard ends of the wheel stud holes are typically counterbored to receive the ends of the wheel retaining nuts. When a wheel is mounted upon a vehicle, the inboard surface of the hub typically contacts a wheel hub. To assure good contact and support between the wheel and the wheel hub, the inboard hub surface is typically faced to form a smooth surface. A plurality of wheel spokes connect the wheel hub to the wheel rim. The wheel spokes support the weight of the vehicle and are designed accordingly. In the past, vehicle wheels have been fabricated by attaching a stamped steel wheel disc to a rolled steel wheel rim. Also in the past, vehicle wheels have been cast from molten steel alloys or forged from steel alloy billets. Increasingly, vehicle wheels are being formed from light weight metals, such as aluminum, magnesium, titanium, or alloys thereof. Such light weight wheels can be formed with the wheel disc having a pleasing aesthetic shape.

The wheel disc outer surface is typically machined to form a smooth surface which can be subsequently finished with a decorative high luster. It is known to form light weight wheels from a one-piece casting or forging. Alternately, light weight wheels can be assembled by attaching a wheel disc to a wheel rim or a full faced wheel disk to a partial wheel rim.

An assembled light weight wheel having a wheel disc and rim formed from dissimilar metals is known as a bimetal wheel. For example, a full faced wheel disc cast or forged from an aluminum alloy and having a specific shape can be welded to a partial wheel rim rolled from a steel alloy. In this example, the use of the aluminum alloy wheel disc allows styling of the visible portion of the assembled wheel while the use of the steel alloy wheel rim reduces the cost of the wheel. To facilitate welding the steel alloy wheel rim to the aluminum alloy wheel disc, it is known to cast a steel alloy weld anchor into the wheel disc. A portion of the weld anchor remains exposed and forms at least a portion of the surface of the wheel disc which contacts the wheel rim. The wheel rim is welded to the weld anchor with the weld anchor providing a compatible material for forming a weld with the steel wheel rim.

All wheels, regardless of the material used to form the wheel, have an outer surface of the wheel disc which is visible when the wheel is mounted upon a car. Accordingly, the wheel disc can be formed having a pleasing aesthetic shape. The wheel disc outer surface is then typically machined to form a smooth surface which is subsequently provided with a surface finish which typically has a decorative high luster. One type of surface finish, which is used extensively, is formed by chrome plating the outer surface of the wheel disc. During chrome plating, a layer of chromium, which can be polished to a high luster, is deposited upon the wheel surface. Known methods for forming a surface layer of chromium on a wheel surface are complex and typically require a number of discrete steps involving chemical deposition of multiple layers of metal onto the surface.

A typical method for chrome plating a wheel is illustrated in the flow chart shown in FIG. 1. In functional block 10, a formed wheel that has been machined to final shape is provided. As shown in block 1 1, the wheel is prepared for chrome plating by first immersing the wheel in a solvent bath. The solvent bath removes oils and dirt, which would inhibit adhesion of metal deposits to the wheel surface. The wheel, in functional block 12, is pretreated

by immersion in a chemical bath to dissolve any surface oxides. This further improves the adhesion of metal deposits to the wheel surface. The wheel is then rinsed, as shown in functional block 13, by immersion in a water bath or spraying with a high pressure water jet. The preparatory steps of removing oil and dirt, dissolving surface oxides and flushing are typically referred to as cleaning the wheel surface.

The chrome plating process begins in functional block 14 with the immersion of the portion of the wheel to be chrome plated in a chemical bath containing nickel in solution. During immersion, a thin layer of nickel is chemically deposited upon on the wheel surface to enhance adhesion of successive metal layers thereto. This prenickel layer tends to have a relatively uneven surface. Accordingly, in functional block 15, a copper layer is chemically deposited, usually by immersion of the wheel surface in another chemical bath which contains cooper in solution, over the prenickel layer. The copper layer fills in uneven portions of the prenickel layer, forming a smooth surface. To further enhance the surface smoothness, the copper layer is buffed, as shown in functional block 16. In functional block 17, a second nickel layer, referred to as a semibright nickel layer is formed by chemical deposition over the buffed copper layer. The semibright nickel layer provides corrosion resistance. Next, in functional block 18, a layer of nickel containing sulfur is chemically deposited over the semibright nickel layer as a sacrificial corrosion layer. In functional block 19, a final bright nickel layer is deposited onto the surface to provide reflectivity and brightness to the wheel surface. The layers of nickel and copper provide a base upon which the chromium layer is deposited. In functional block 20, a prechromium layer is deposited over the bright nickel layer. This layer is formed from discontinuous chrome, or pixy dust, to provide a more durable surface layer. Finally, in functional block 21 , a layer of chromium is deposited to prevent nickel fogging.

During the chrome plating process, each successive metal layer is typically formed by immersing the portion of the wheel surface to be chrome plated in a chemical bath containing a solution of the particular metal to be deposited on the wheel surface. Thus, each layer is chemically bonded to the preceding layer to provide a durable and attractive decorative surface coating on the wheel. Known methods for forming other types of wheel surface

finishes are similar to the above described chrome plating process and typically include a number of discrete steps.

SUMMARY OF THE INVENTION This invention relates to a method for forming a metal surface layer upon a vehicle wheel which utilizes an arc plasma thermal spray to spray droplets of molten metal onto the wheel surface

The method includes providing a finished wheel or wheel component that has been prepared by removing any dirt, oil and oxides from the portion of the wheel surface that is to received the surface finish. A metal layer is formed on the prepared surface with a thermal spray gun. The thermal spray gun generates a plasma plume. A powder consisting of very small metal particles, such as nickel or stainless steel particles, is introduced into the plume. The high temperature of the plasma plume melts the individual metal particles to form droplets of molten metal. The molten metal droplets are sprayed onto the wheel surface to form a layer of the metal. The droplets fuse to a portion of the wheel surface and form a strong physical bond with the wheel surface upon cooling. Because of their small size, the droplets form a surface layer having a fine grain structure. The thickness of the metal layer is proportional to the duration of the thermal spraying and can vary from 5 microns to 0.25 inches (0.64 cm). Depending upon the particular application, a second layer of metal can be thermally sprayed over the first metal layer. However, in certain applications, one layer of metal is sufficient. Additionally, the second metal layer can be formed from a metal that is dissimilar to the metal used in the first layer.

The sprayed metal layer can be polished to a high luster and covered with a coating, such as an organic coating of paint or clear coat, for an attractive appearance. Alternatively, a final finish layer of metal can be applied over the thermally sprayed metal layer. For example, a layer of chromium or other metal can be deposited over the sprayed metal layer with conventional chemical plating methods or by thermal spraying. One or more layers of metal can be chemically deposited over the sprayed metal layer. When multiple layers of chromium are chemically deposited on the wheel, one of the chromium layers can include pixy dust to provide a more durable chromium surface. Additionally, a layer of paint can be applied to the wheel surface.

With respect to bimetal wheels, visible portions of the wheel rim are thermally sprayed with a metal which is compatible with the metal used to form the wheel disc. The resulting sprayed metal layer can be machined or polished to match the appearance of the wheel disc. The sprayed metal layer can be extended to cover the portion of the wheel rim which contacts the wheel disc. This extended portion forms a weld anchor for the weld securing the wheel disc to the wheel rim.

As an alternate to welding, the wheel disc can be brazed to the wheel rim. A layer of filler metal which is compatible with both the wheel disc and the wheel rim is thermally sprayed onto the wheel rim. The wheel disc is positioned in contact with the sprayed metal layer to form a wheel assembly. The wheel assembly is heated to melt the layer of filler metal. Upon cooling, a brazed joint is formed between the wheel disc and the wheel rim.

Additionally, the wheel rim can be clamped into a full face wheel disc mold with the sprayed portion of the rim extending into the mold cavity. The wheel disc is then cast over the sprayed portion of the wheel rim. Upon cooling, the casting bonds to the sprayed metal layer to form a secure air-tight seal between the wheel disc and the wheel rim. Alternately, the wheel rim can be mounted on a full face wheel disc die set with the sprayed portion of the rim extending into the die cavity. A heated metal billet is inserted between the dies and dies closed, forging the wheel disc over the sprayed portion of the wheel rim. Upon cooling, the forging bonds to the sprayed metal layer to form a secure air-tight seal between the wheel disc and the wheel rim. The invention also contemplates thermally depositing a layer of material onto portions of a vehicle wheel rim drop well. The resulting layer has a greater density than the adjacent metal and reduces the porosity of the drop well.

Additionally, a layer of material can be deposited onto the surface of at least one of the tire bead seats of a vehicle wheel. The deposited layer of material defines a surface having a coefficient of friction which is greater than the coefficient of friction of the wheel rim surface.

A layer of material can be thermally deposited on the inboard surface of a vehicle wheel hub. The deposited layer of material seals the wheel hub surface, thereby protecting the surface from potential corrosion.

Material which is harder than the wheel hub material can be thermally deposited in the wheel lug holes to provide a harder bearing surface for the wheel retaining nuts.

The invention further contemplates thermally depositing a mixture of a metal and a reinforcing material onto portions of the wheel to form a metal matrix composite reinforcing layer.

Accordingly, it is an object of the invention to provide an improved method for forming a surface finish on a portion of a wheel surface which utilizes thermal spraying technology and is simpler than prior art methods. It is a further object of the invention to improve the fabrication of a bimetal wheel by thermally spraying a surface layer of metal on the portion of the wheel rim adjacent to the wheel disc which is compatible with the metal used to form the wheel disc.

It is another object of the invention to provide an improved vehicle wheel by thermally depositing a layer of material onto a portion of the wheel drop well surface.

Other objects and advantages of the invention will become apparent from the following detailed description of the invention and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a flow chart of a method for chrome plating a vehicle wheel in accordance with the prior art.

Fig. 2 is a flow chart of a method for forming a surface finish on a vehicle wheel in accordance with the present invention. Fig. 3 is a sectional view of an arc plasma spray gun used in the thermal coating steps shown in FIG. 2.

Fig. 4 is a flow chart for an alternate embodiment of the method for forming a surface finish shown in FIG. 2.

FIG. 5 is a flow chart of another embodiment of the method for forming a surface finish shown in FIG. 2.

FIG. 6 is a flow chart of an alternate method for forming a surface finish on a vehilce wheel in accordance with the present invention.

FIG. 7 is a flow chart of another embodiment of the method for forming a surface finish shown in FIG. 6. FIG. 8 illustrates forming a weld anchor on an inner surface of a wheel rim in accordance with the invention.

FIG. 9 shows a wheel spider welded to the wheel rim shown in FIG. 8.

FIG. 10 illustrates forming a weld anchor on the inner surface of a wheel rim drop well in accordance with the invention.

FIG. 1 1 shows a wheel disc welded to the wheel rim shown in FIG. 10.

FIG. 12 is a fragmentary sectional view of a full face wheel disc having a weld anchor formed on a portion of the deep in accordance with the invention.

FIG. 13 is a fragmentary sectional view of a partial wheel rim welded to the wheel disc shown in FIG. 12.

FIG. 14 is a fragmentary sectional view of a full face wheel disc having an annular weld anchor formed on an inboard surface in accordance with the invention.

FIG. 15 is a fragmentary sectional view of a partial wheel rim welded to the wheel disc shown in FIG. 14.

FIG. 16 is a fragmentary sectional view of a full face wheel fabricated in accordance with the invention.

FIG. 17 is a flow chart of the method for fabricating the wheel shown in FIG. 16.

FIG. 18 is a sectional view of a wheel mold for casting the wheel disc shown in FIG. 16. FIG. 19 is a flow chart of an alternate method for fabricating the wheel shown in FIG. 16.

FIG. 20 is a sectional view of a set of wheel dies for semi-solid forging the wheel disc shown in FIG. 16.

FIG. 21 is an alternate embodiment of the bimetal wheel shown in FIG. 16.

FIG. 22 is a fragmentary sectional view of an alternate embodiment of the wheel shown in FIG. 16.

FIG. 23 is a fragmentary sectional view of another embodiment of the wheel shown in FIG. 16. FIG. 24 is a fragmentary sectional view of a vehicle wheel having a layer of metal deposited on the surface of the drop well in accordance with the invention.

FIG. 25 is a fragmentary sectional view of a vehicle wheel having layers of metal deposited on the surfaces of the tire bead seats in accordance with the invention.

FIG. 26 is a fragmentary sectional view of a vehicle wheel having a layer of material deposited upon the wheel hub mounting surface in accordance with the invention.

FIG. 27 is a fragmentary sectional view of a vehicle wheel having a layer of material deposited upon the wheel lug hole surface in accordance with the invention.

FIG. 28 is a sectional view of an alternate embodiment of the arc plasma spray gun shown in FIG. 3.

FIG. 29 is a fragmentary sectional view of a vehicle wheel having a layer of a metal matrix composite material deposited upon an inner surface in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring again to the drawings, there is shown in FIG. 2 a flow chart of an improved method for forming a surface finish on a vehicle wheel. Typically, the surface finish will be applied to the outer surface, or face, of the wheel disc, however, portions of the wheel rim or the entire wheel also can be covered. While in the preferred embodiment the method is used to form a decorative surface, the method also can be used, as will be described below, to form other surface finishes. For illustrative purposes, the method as shown in FIG. 2 is for forming a chromium surface finish on a portion of the wheel. However, as will be described below, the method is applicable for forming other surface finishes.

The method starts with provision of a wheel (not shown), as shown in functional block 25. The wheel can be formed by conventional casting methods, including low pressure, die or squeeze casting, forging, semi-solid forging, stamping or any other conventional method of wheel fabrication. Furthermore, the wheel can be formed as a single piece or assembled from multiple pieces of the same or dissimilar metals. It will be appreciated that the method can be applied to wheels formed from light weight metals, such as aluminum, magnesium and titanium, and alloys thereof and alloys of other light weight metals. The method also is applicable to wheels stamped from steel sheet stock, cast from steel or formed by other conventional steel wheel production methods. Finally, the method can be applied to a complete wheel after fabrication or to a wheel component before it is assembled into a complete wheel.

With respect to wheels formed from light weight metals, the wheels provided in functional block 25 are machined to form a pilot hole and wheel stud holes extending through the wheel hub. Additionally, the inside and outside wheel rim surfaces are machined to final shape. As part of the machining process, the face of the wheel disc can be machined to form a smooth surface finish. Alternatively, the machining of the outer surface, or face, of the wheel disc can be omitted. When the face is not machined, the face can be shot peened to provide a uniform surface finish. However, shot peening is optional and is not required for successful application of the invention.

In functional block 26, the wheel is cleaned to remove dirt, oil and any surface oxides. Cleaning includes the conventional steps, shown in functional blocks 11, 12 and 13 of FIG. 1, and includes immersion of the wheel in a solvent to remove dirt and oil, immersion in a chemical bath to remove oxides and rinsing to remove any solvent and chemicals. The rinse can be by immersion in a water bath or by flushing with a water jet.

The method includes an optional step, shown in functional block 27, of applying a layer of copper to the portion of the wheel surface which is to receive the bright decorative layer. The copper layer provides a smooth surface for the bright decorative layer. Inclusion of a copper layer is dependent upon the surface condition of the wheel and the thickness of the layers to be applied subsequent to the copper layer. A conventional method of copper plating, such as partial or total immersion of the wheel in a chemical bath, can be used to deposit the copper layer upon the wheel surface.

As shown in functional block 28, a semibright nickel layer is deposited upon the wheel surface by a thermal spray means. Thermal spray means are commercially available and include a plasma generator as a thermal and kinetic energy source for spraying droplets of molten materials against an appropriate surface. In the preferred embodiment, an arc plasma spray gun is used.

A sectional view of a typical arc plasma spray gun is shown generally at 30 in FIG. 3. The spray gun 30 includes a housing 31 that defines a cylindrically shaped arc chamber 32 and also forms a first electrode. A nozzle 33 connects the arc chamber 32 to the atmosphere. A second electrode 34 extends axially into the arc chamber 32. The housing 31 includes an internal cooling passage 35 formed therein which conveys cooling water

around the arc chamber 32 to cool the housing 31. A cooling water inlet port 36 connects the cooling water passage 35 with a supply of cooling water (not shown) while a cooling water outlet port 37 connects the cooling passage 35 with a water discharge hose (not shown). Cooling water is circulated through the cooling passage 35 when the spray gun 30 is operated. A gas inlet port 38 connects the arc chamber 32 to a supply of a mixture of pressurized inert gases, such as argon and nitrogen. A material inlet port 39 communicates with the nozzle 33 downstream from the arc chamber 32 and is connected to a pressurized supply of a powdered metal (not shown) that is to be sprayed onto the surface.

To operate the arc plasma spray gun 30. a DC arc (not shown) is struck between the spray gun electrodes 31 and 34. The arc has a maximum temperature of approximately 1,600° C. The arc temperature causes a rapid expansion of the inert gas mixture supplied through the gas inlet port 36 to form a plume 40 of ionized gases. The plume of ionized gases 40 is discharged through the nozzle 33. Powdered nickel, entrained in a carrier gas, such as helium, is injected under pressure through the material inlet port 39 into the plasma plume 40 in the nozzle 33. The powdered nickel includes very small particles which the temperature of the plasma melts to form small droplets of molten nickel. The nickel droplets are carried by the plasma plume 40 which is directed at a surface 41 of a wheel 42, shown in fragmentary section in FIG. 3. The nickel droplets splatter onto the surface 41 of the wheel 42 to form a layer 43 of nickel. The nickel droplets and wheel surface cool rapidly, fusing the nickel to the wheel surface 41 and causing the nickel layer 43 to have a strong physical bond with the wheel surface. The rapid cooling causes the nickel layer 43 to have a small grain size. Because of the small grain size, the nickel layer 43 has a high density, typically approximately 99 percent, and a corresponding low porosity. The low porosity inhibits liquid penetration of the nickel layer 43, thereby protecting the wheel 42 from corrosion.

.Λ.S additional nickel droplets are sprayed onto the wheel surface 41. they are fused to the initially deposited nickel to increase the thickness of the nickel layer. The final thickness of the nickel layer 43 is proportional to the applied arc power, the flow of the nickel and the duration of the thermal spraying step. The thickness of the nickel layer 43 deposited depends upon the specific application for the wheel and can vary between 5 microns and 0.25 inches (0.64 cm).

During coating, the spray gun 30 is moved relative to the wheel surface 41 to assure a uniform formation of the nickel layer 43. The spray gun 30 can be traversed across the wheel surface 41. Alternatively, die wheel 42 can be rotated before a stationary spray gun 30, or the spray gun 30 can be traversed past a rotating wheel 42.

It will be appreciated tiiat other commercially available thermal spraying means can be used to form the nickel layer 43. For example, an electric arc gun with a nickel wire or rod fed into the plasma plume or a high velocity oxygen hydrocarbon fuel spray gun could be used to spray the nickel droplets onto the wheel 42.

In functional block 44 in FIG. 2, a bright nickel layer is applied over the semibright layer with the thermal spray means. As indicated in functional block 28 of Fig. 2. the semi-bright nickel layer is optional and application thereof is dependent upon the surface conditions of the particular wheel, the expected wheel service conditions and the desired total thickness of the nickel coating. When the semibright nickel layer is omitted, only one layer of nickel is thermally sprayed onto the wheel surface 41.

In functional block 45, the bright nickel layer is polished, however, the polishing is optional. In functional block 46, a layer of chromium is deposited over the nickel using conventional chrome plating means. The chrome plating can consist of applying a single layer of chromium or of applying successive layers of pixy dust and chromium, with the pixy dust applied either before or after the chromium. It will be appreciated that the surface layer can include a combination of chromium and nickel or other metals used in conventional chrome plating processes. Additionally, while the above description indicates that a thermal spray gun is only used to apply the nickel layers, it will be appreciated that a thermal spray gun also can be used to apply the other metal layers. Thus, if a copper layer is desired, it can be formed either by chemical deposition or by thermal spraying. Likewise, the chromium can be applied with a thermal spray gun.

Thus, the present invention provides a simplified method for forming a durable decorative layer of chromium over a portion of a wheel surface. The reduction of discrete steps required to form the decorative layer significantly reduces the complexity of finishing the wheel. An alternate embodiment of the present invention can be used to apply other finishes to a wheel, as illustrated in FIG. 4. As shown in functional blocks 47 and 48. the alternate embodiment of the method begins with

provision and cleaning of a wheel. Then, in functional block 49, a thermal spray applies a metal layer selected for the particular wheel directly to the wheel surface. For example, instead of nickel, powered aluminum, which can include pure aluminum or an aluminum alloy, can be supplied to the plasma arc spray gun 30.

As indicated above, the applied layer thickness is a function of the applied arc power, the rate of feed for the material being sprayed and the duration of the thermal spraying. If the dimensions of the wheel are critical, the metal surface can be built up with a thick sprayed metal layer which is subsequently machined to the final shape. This machining operation is shown as an optional step in functional block 50 and can be used to compensate for dimensional variations inherent in the wheel fabrication process.

Next the wheel is polished to a high gloss, as shown in functional block 51. In the preferred embodiment, a clear coating is applied to the wheel surface as shown in functional block 52. However, under certain conditions, the clear coat may be omitted. For example, it may not be desirable to clear coat the wheel carrying a vehicle spare tire.

The alternate embodiment can be used to apply a polished aluminum finish to light weight wheels formed from aluminum, magnesium, titanium or alloys thereof. It is believed that thermally spraying aluminum onto a aluminum or aluminum alloy wheel can reduce the porosity of the wheel. The low porosity of the aluminum surface finish reduces bubbling in any paint or clear coatings that are subsequently applied to the wheel, thereby reducing wheel rejections. By thermally spraying a layer of predesigned or prescribed aluminum onto the wheel surface and then polishing the aluminum layer, a high luster can be achieved. It is believed that the polished the sprayed surface has a brighter appearance than conventionally finished aluminum or aluminum alloy wheels. Additionally, powdered stainless steel can be supplied to the arc plasma gun 30 to form a stainless steel surface layer on steel fabricated, stamped or cast wheels.

Another alternate embodiment of the present invention is shown in FIG. 5 where the method of the present invention is used to apply a surface finish to a wheel formed from magnesium. In functional block 53, a wheel formed from a magnesium alloy is provided. In functional block 54, the wheel surface is cleaned to remove oil, dirt and any oxides in preparation for spraying. In functional block 55, the wheel is mounted upon a first fixture (not shown) and the outside surfaces of the rim and wheel disc are thermally

sprayed with molten aluminum droplets. The droplets physically and chemically bond to the magnesium wheel surface to form a covering layer of aluminum. In functional block 56, the wheel is transferred to a second fixture (not shown) to expose the unsprayed inside surfaces of the rim and wheel disc. These unsprayed surfaces are then thermally sprayed with molten aluminum droplets. The entire wheel surface is sprayed with aluminum to seal the magnesium within an aluminum layer, or coating, thereby protecting the magnesium from corrosion. The aluminum coating is especially durable because of the physical bond formed between the molted aluminum droplets and the magnesium wheel surface. Additionally, as described above, the low porosity of the aluminum surface finish reduces bubbling in any paint or clear coatings that are subsequently applied to the wheel, thereby reducing wheel rejections.

Following the thermal spraying, the wheel can be polished in functional block 57, however, this step is optional. The luster achieved during polishing is directly proportional to the duration of the polishing and inversely proportional to the size of the polishing medium. At this point, the wheel appears to be formed from aluminum or an aluminum alloy. If desired, the wheel can be painted, as indicated in functional block 58. For example, painting can restore a magnesium appearance to the wheel. Finally, in functional block 59, a clear coating is applied to the wheel by conventional means to further seal the wheel surface.

The method also can be applied to thermally spray an anodized friendly alloy onto an anodized wheel. Additionally, a corrosion resistant coating can be formed upon a wheel by thermally spraying a ceramic material onto the wheel surface. The resulting coating will typically not have a bright luster, however, an optional coat of paint can be applied thereover.

An alternate method for forming a surface finish on a vehicle wheel in accordance with the present invention is illustrated by the flow chart shown in FIG. 6. In the preferred embodiment, an aluminum alloy wheel is provided in functional block 60. In functional block 61, the wheel surface is cleaned, as described above, in preparation for thermal spraying. A layer of stainless steel is deposited onto the cleaned wheel surface with a thermal spray gun in functional block 62. The resulting stainless steel layer appears similar to chrome plating. In the preferred embodiment, an arc plasma spray gun, as shown in FIG. 3 is used to deposit the stainless steel; however, other thermal spray means can be used. The stainless steel forms a highly corrosion

resistant surface on the aluminum alloy wheel, sealing the wheel surface from corrosion. In the preferred embodiment, only the visible portions of the wheel, such as the outboard face of the wheel disc and the outboard portion of the wheel rim, are sprayed with stainless steel. However, it will be appreciated that the entire wheel can be sprayed with stainless steel.

To further enhance the appearance of the wheel, the stainless steel surface may be polished to a high luster, as shown in functional block 63; however, this step is optional. As described above, in the preferred embodiment, only a portion of the wheel is sprayed with stainless steel. Thus a boundary is formed between the stainless steel and the metal forming the wheel which is exposed to the environment. Under certain conditions, galvanic action may occur along the boundary. This galvanic action could result in corrosion. Accordingly, a coating can be applied to the wheel surface in functional block 64 to seal the boundary. In the preferred embodiment, an organic coating. such as a clear coating or a paint, is used to seal the boundary. Similarly, if the entire wheel is thermally sprayed with stainless steel, a coating can be applied to the wheel surface to seal the stainless steel layer. In the preferred embodiment, an organic coating, such as a clear coating or a paint, is used to seal the wheel surface. As shown in FIG. 6, this step can be optional.

An alternate embodiment of the above method for forming a surface finish on a vehicle wheel is illustrated by the flow chart shown in FIG. 7 Similar to the method shown in FIG. 6, an aluminum alloy wheel is provided in functional block 65. In functional block 66, the wheel surface is cleaned in preparation for thermal spraying. A base layer of stainless steel is deposited onto the cleaned wheel surface with a thermal spray gun in functional block 67. In functional block 68, a cover layer of chromium is deposited onto the stainless steel base layer. The chromium cover layer can be chemically deposited onto the wheel surface by a conventional method. Alternately, the chromium cover layer can be thermally sprayed onto the wheel surface. It is believed that the corrosion resistance of the stainless steel base layer will be more durable than conventional base layers if the chromium cover layer is damaged. As described above, in the preferred embodiment, only the visible portions of the wheel, such as the outboard face of the wheel disc and the outboard portion of the wheel rim. are sprayed with stainless steel and subsequently receive a cover layer of chromium. However, it will be

appreciated that the entire wheel can be sprayed with stainless steel and covered with chromium.

When only a portion of the wheel is sprayed with stainless steel and covered with chromium, a boundary is formed between the stainless steel and chromium surface finish and the metal forming the wheel. This boundary can be exposed to the environment. Under certain conditions, galvanic action may occur along the boundary. This galvanic action could result in corrosion. Accordingly, a coating can be applied to the wheel surface in functional block 69 to seal the boundary. In the preferred embodiment, an organic coating, such as a clear coating or a paint, is used to seal the boundar '. Similarly, if the entire wheel is thermally sprayed with stainless steel and covered with chromium, a coating can be applied to the wheel surface to seal the chromium cover layer. In the preferred embodiment, an organic coating, such as a clear coating or a paint, is used to seal the chromium cover layer. As shown in FIG. 7, this step can be optional.

Thus, it is possible to form a surface finish on a vehicle wheel consisting of only a stainless steel layer and an optional organic coating or of a combination of stainless steel layer covered by a chromium layer which is optionally covered by an organic layer. Both of these methods of forming a surface finish require significantly fewer steps than conventional known means for chrome plating a vehicle wheel.

While an aluminum alloy wheel has been described to illustrate the preferred embodiment of the invention, it will be appreciated that the invention can be practiced on wheels formed from alloys of other light weight wheels, such as magnesium and titanium.

While the invention has been described above in terms of forming a surface finish upon a vehicle wheel, it is understood that the present invention can be used to form a decorative finish on components other than wheels. Such a decorative finish can be formed by thermally spraying a layer of metal onto the component and then finishing the surface of the sprayed layer.

The present invention further contemplates enhancing the appearance of a bimetal vehicle wheel by thermal spraying a layer of the same metal used to form the wheel disc onto the surface of the visible portion of a wheel rim formed form a dissimilar metal, as illustrated in FIG. 8. The thermally sprayed layer of metal also forms a weld anchor for securing a wheel disc to the wheel rim.

The present invention contemplates using a thermal spray gun to deposit a layer of metal on a portion of the surface of the wheel rim 70 to form a weld anchor. As will be explained below, a wheel disc formed from a metal which is different from the wheel rim metal is welded to the weld anchor to form a bimetal vehicle wheel. Accordingly, the weld anchor is formed from a metal which is compatible with the wheel disc metal. The invention also contemplates enhancing the appearance of the assembled bimetal vehicle wheel by extending the thermally sprayed layer of metal across any visible portion of the wheel rim. A fragmentary cross section view of a full wheel rim 70 is shown in

FIG. 8. In the preferred embodiment of the invention, the wheel rim 70 is formed from steel by a conventional process, such as butt welding the ends of a strip of steel to form a hoop and rolling or spinning the hoop to a final shape. The rim 70 has an inner surface 70 A and includes a ring shaped outboard tire bead retaining flange 71 which defines an outboard flange surface 72. The bead retaining flange 71 is contiguous to an annular outboard tire bead seat 73. The bead seat 73 defines an inner surface 74. The outboard bead seat 73 is contiguous with a radial outboard drop well wall 75 which defines an outboard surface 76. The drop well wall 75 is contiguous with an annular drop well 77, which defines an inner surface 78. The drop well 77 extends axially to an annular rim leg portion 79. The inboard end of the leg portion 79 terminates in an annular inboard tire bead seat 80. A ring shaped inboard tire bead retaining flange 81 is formed on the inboard end of the inboard tire bead seat 80. The portion of the wheel rim inner surface 70A which is to be sprayed is cleaned of any dirt, oil and oxides to assure a good bond between the sprayed metal and the surface. A thermal spray gun 85 sprays a layer of metal 86 onto the cleaned portion of the rim inner surface. In the preferred embodiment, an arc plasma spray gun, as shown in FIG. 3 is used, however, other types of thermal spray guns can be used. In the preferred embodiment, powdered aluminum is supplied to the thermal spray gun 85 to form the metal layer 86, for reasons which will be explained below.

Initially, the spray gun 85 is in a position labeled "A" in FIG. 8 to spray a first portion 87 of the metal layer 86 onto the outboard flange surface 72 of the outboard tire bead retaining flange 71. The spray gun 85 can be rotated and translated axially to a second position labeled "B" to spray a second portion 88 of the metal layer 86 over the inner surface 74 of the

outboard tire bead seat 73. While the thermal spray gun 85 sprays, the wheel rim 70 is rotated about its axis. To enhance uniformity of the sprayed metal layer 86, the spray gun 85 can be mounted upon a robotic arm (not shown). The robotic arm is controlled to follow the surface contours of the wheel rim 70 and to maintain a predetermined distance between the spray gun nozzle (not shown) and the wheel rim surface as the gun moves axially. As shown in FIG. 8, the metal layer 86 extends onto the outboard surface 76 of the drop well 77 to form a weld anchor 88. The weld anchor 88 is formed having a greater thickness than the first portion 87 of the sprayed metal layer 86. It will be appreciated that the metal layer 86 can extend partially across the inner surface 70A of the wheel rim 70 to cover those portions of the inner surface which are visible after the wheel disc is attached to the wheel rim 70. Alternately the metal layer 86 can extend axially across the entire inner surface 70 A of the wheel rim 70. As indicated above, the applied layer thickness is a function of the applied arc power, the rate of feed for the material being sprayed and the duration of the thermal spraying. If the dimensions of the wheel are critical, the metal surface can be built up with a thick sprayed metal layer which is subsequently machined to the final shape; however, such machining is optional. Machining is typically needed where tolerances are close or it is desired to match a machined surface on the wheel disk that is to be attached to the wheel rim 70. Similarly, the metal layer 86 can be polished to a high luster, however, polishing is also optional.

A fragmentary section view of an assembled bimetal vehicle wheel 90 which was formed in accordance with the invention is shown in FIG. 9. The wheel 90 includes the wheel rim 70. The identification numerals used in FIG. 9 to identify portions of the wheel rim 70 are the same as used in FIG. 8. A wheel disc 91, which in the preferred embodiment is formed from aluminum or an aluminum alloy by a conventional means, such as casting or forging, is disposed in the outboard portion of the wheel rim 70. The wheel disc 91 includes a central hub 92 which has a central pilot hole 93 and a plurality of wheel stud holes 94, only one of which is shown, formed therethrough. A plurality of spokes 95, two of which are shown, extend radially outward from the hub 92 to the wheel rim 70. Each wheel spoke 95 terminates in an outer portion 96 which contacts the second portion 88 of the wheel rim metal layer 86. Thus, the wheel disc 91 defines a wheel spider.

The wheel disc 91 is secured to the wheel rim 70 by welding the spoke end poπions 96 to the inner surface 74 of the outboard tire bead seat 73. The welds 97 are formed between the spoke end portions 96 and the weld anchor 88. The welds 97 can consist of a single spot weld on the end of each wheel 5 spoke 96. Alternately, the welds 97 can extend around the circumference of the spoke ends 96 or be formed as a butt joint along the interface between the spoke end portions 96 and the weld anchor 88. Because the weld anchor 88 is formed from aluminum or an aluminum alloy which matches the metal used ro form the wheel disc 91, the welds 97 securing the end poπions 96 of the C aluminum wheel spokes 95 to the weld anchor 88 are easily formed.

Furthermore, as explained above, thermal spraying the metal layer 86 onto the wheel rim 70 assures that the weld anchor 88 is securely attached to the surface of the wheel rim 70

As indicated above, the weld anchor 88 is formed thicker than the first 5 portion 87 of the metal layer 86. However, depending upon the specific conditions, the weld anchor 88 may have the same thickness as the first portion 87. Additionally, while the weld anchor 88 has been described as being a continuous circumferential ring, it as also possible to form an individual weld anchor (not shown) that corresponds to each wheel spoke end 0 portion 96. Such individual weld anchors would be equally spaced about the circumference of the inner surface 74 of the outboard tire bead seat 73. While use of individual weld anchors would reduce the amount of metal sprayed onto the wheel rim 70, careful alignment of the wheel disk spokes 95 with the welding anchors would be required when the wheel 90 is assembled. While the thermally deposited metal layer 86 and the wheel disc 91 have been described above as being formed from aluminum, it will be appreciated that other metals and metal alloys can be used to practice the invention. Generally, the metal sprayed onto the wheel rim to form the metal layer 86 must be compatible for welding to the metal used to form the wheel disc 91 in the sense of being weldable thereto. Accordingly, an alloy of the wheel disc material can be used, as long as welding compatibility exists. Machining or polishing of the first portion 87 of the metal layer 86 assures that the visible portion of the wheel rim 70 visually matches the wheel disc 91. Thus, the wheel 90 appears to be formed entirely from the metal used to form the wheel disc 91.

It will be further appreciated that the above method of wheel assembly can be applied to any bimetal wheel. Thus, the wheel rim 70 can be formed

by other conventional processes, such as casting or forging. Additionally, while the wheel rim 70 has been described as being formed from steel, the rim 70 also can be formed from a light weight metal or alloy thereof which differs from the metal used to form the wheel disc 91. Similarly, while the wheel disc 91 was described above as being formed from aluminum or an aluminum alloy, it will be appreciated that other light weight metals, such as magnesium or titanium, or alloys thereof can be used to form the wheel disc 91.

An alternate embodiment of the above method for fabricating a bimetal vehicle wheel is illustrated in FIGS. 10 and 1 1. For illustrative purposes, the same steel rim 70 shown in FIGS. 8 and 9 is used. A fragmentary sectional view of the wheel rim 70 is shown in FIG. 10. The portions of the wheel rim 70 are labeled with the same numeric designators used in FIG. 8. In the preferred embodiment, a thermal spray gun 85 is used to form two separate layers of sprayed aluminum or aluminum alloy on the inner surface of the wheel rim 70.

A ring shaped outer layer 101 is formed with the spray gun 85 traversing axially from the position labeled "C while the rim 70 is rotated about its axis. The first ring 101 extends radially across the outboard surface 72 of the outboard tire bead retaining flange 71 and axially across a portion of the inner surface 74 of the outboard tire bead seat 73. As described above, the first ring 101 can be machined an 'or polished to match the wheel disc, however, these steps are optional.

The ring shaped weld anchor 102 is formed with the spray gun 85 traversing axially from the position labeled "D" while the rim 70 is rotated about its axis. The weld anchor 102 extends axially across a portion of the inner surface 78 of the drop well 77 to form a weld anchor. The weld anchor 102 is machined as required by wheel disc tolerances.

A fragmentary sectional view of an assembled bimetal vehicle wheel 103 is shown in FIG. 11. The wheel 103 includes a wheel disc 105, which, in the preferred embodiment, is formed from aluminum or an aluminum alloy by a conventional means, such as casting or forging. The wheel disc 105 is disposed in the outboard end of the wheel rim 70. The wheel disc 105 includes a wheel hub 106 which has a central pilot hole 107 and a plurality of wheel stud holes 108, only one of which is shown, formed therethrough. A plurality of spokes 109, two of which are shown, extend radially outward from the hub 106 to an annular disc rim 1 10. The wheel disc rim 110

includes an outboard portion 111 and an inboard portion 112. The inboard portion 112 extends axially into the wheel rim 70 and terminates in an annular edge portion 113. The annular edge portion 1 13 also includes an optional annular recess 114 formed in the outer surface thereof to provide clearance for the weld anchor 102 during assembly of the wheel 103. When the wheel 103 is assembled, the inboard portion 1 12 of the wheel disc rim 110 is supported by the inner surface 78 of the drop well 77.

The wheel disc 105 is secured to the wheel rim 70 with at least one spot weld 115. In the preferred embodiment, a plurality of spot welds 1 15 are used. The spot welds 1 15 are equally spaced circumferentially about the annular edge portion 113. The welds 1 15 are formed between the annular edge portion 1 13 and the weld anchor 102. Because the rim 70 is formed as an air tight subassembly, an air tight seal is not needed between the wheel disc rim 110 and the wheel rim 70. However, the invention can also be practiced by forming a continuous circumferential weld about the disc annular edge portion 1 13.

While the wheel 103 has been described as having a steel rim 70, it will be appreciated that the wheel rim 70 can be formed from a metal or alloy other than steel. Additionally, the wheel disc 105 can be formed from other light weight metals, such as magnesium and titanium or alloys thereof.

Accordingly, the sprayed metal forming the weld anchor 102 is selected to be compatible with the metal used to form the wheel disc 105.

Another embodiment of the invention which contemplates thermally depositing a weld anchor on full face wheel disc is illustrated in FIGS. 12 and 13. FIG. 12 shows a fragmentary sectional view of a full face wheel disc 120 which is formed from aluminum, or an alloy of aluminum by a conventional process, such as casting or forging. The wheel disc 120 includes a wheel hub 121 which has a central pilot hole 122 and a plurality of wheel stud holes 123, only one of which is shown, formed therethrough. A plurality of spokes 124, two of which are shown, extend radially outward from the hub 121 to an annular disc rim 125. The wheel disc rim 125 is formed to include an outboard tire bead retaining flange 126, an outboard tire bead seat 127, a drop well wall 128 and a portion of a drop well 129. The inboard end of the drop well portion 129 forms an annular edge 130. An annular weld anchor 131 is formed on the annular edge 130 of the wheel disc 120 with a thermal spray gun 85. shown in phantom in FIG. 12. In the preferred embodiment, a powered ferrous material is supplied to the

thermal spray gun 85 to form a weld anchor 131 that is compatible for welding to a steel partial wheel rim. The thermal spray gun 85 can be held stationary while the wheel disc 120 is rotated about its axis to form the weld anchor 131. A fragmentary sectional view of an assembled full face vehicle wheel

135 is shown in FIG. 13 which includes a partial wheel rim 136. In the preferred embodiment, the partial wheel rim 136 is formed from steel stock by a conventional process, as described above. The partial wheel rim 136 includes a portion 137 of the drop well having an axially outward directed end terminating in an annular shaped outer edge 138. The drop well portion 137 extends axially to an annular rim leg portion 139. The inboard end of the leg portion 139 terminates in an annular inboard tire bead seat 140. A ring shaped inboard tire bead retaining flange 141 is formed on the inboard end of the inboard tire bead seat 140. To assemble the vehicle wheel 135, the wheel rim 136 is positioned coaxially with the full face wheel disc 120 with the inboard tire bead retaining flange 141 parallel to the outboard tire bead retaining flange 126 and the wheel rim outer edge 138 abutting the weld anchor 131. The wheel rim

136 is secured to the wheel disc 120 with a continuous circumferential butt weld formed between the wheel rim outer edge 138 and the weld anchor 131.

The wheel 135 illustrated in FIG. 13 has an outer weld 142 and an inner weld 143. However, it will be appreciated that the wheel 135 can be assembled with only one weld, either the outer weld 142 or the inner weld 143. It may be desirable to grind or machine the outer weld 142 flush with the outer surface of the drop well 137, however this step is optional. The weld must be air tight to prevent air leakage when a tire is mounted upon the wheel 135. Because of the strong physical bond formed between the thermally sprayed weld anchor 131 and the wheel disc 120, leakage of air past the weld anchor is expected to be less than the air leakage typically experienced with prior art weld anchors that are cast or forged into the wheel disc.

While the vehicle wheel 135 has been described as having a steel partial rim 136, it will be appreciated that the wheel rim 136 also can be formed from a light weight metal or alloy thereof which is dissimilar to the metal used to form the wheel disc 120. In such situations, the weld anchor 131 is formed from a metal that is compatible with the metal used to form the wheel rim 136. Furthermore, the wheel rim 135 can be formed by a casting or forging operation. Similarly, the wheel disc 120 can be formed from other

light weight metals or alloys than aluminum. Additionally, while the invention has been illustrated with the weld anchor 131 formed on the wheel disc 120, the weld anchor can, as an alternative, be formed upon the wheel rim 136. For example, if the wheel disc 120 is formed from an aluminum alloy and the wheel rim from steel, a layer of aluminum or aluminum alloy can be sprayed onto the wheel rim outer edge 138 to form a weld anchor (not shown). The sprayed aluminum adheres to the steel wheel rim 136 forming a weld anchor thereon to which the wheel disc 120 can be welded.

Another embodiment of the thermally deposited weld anchor 21 is illustrated in FIGS. 14 and 15. A fragmentary sectional view of a full face wheel disc 150 is shown in FIG. 14. In the preferred embodiment, the wheel disc 150 is stamped from a sheet of aluminum or an alloy of aluminum, however, it will be appreciated that the wheel disc also can be cast or forged. .Additionally, other metals or alloys than aluminum can be used to form the wheel disc 150. The wheel disc 150 includes a wheel hub 151 which has a central pilot hole 152 and a plurality of wheel stud holes 153. only one of which is shown, formed therethrough. The wheel disc 150 extends radially outward from the hub 151 to an annular wheel disc rim 155. The wheel disc rim 155 defines an annular inner radial surface 156 and is formed to include an outboard tire bead retaining flange 157.

An annular weld anchor 160 is formed on the annular inner surface 156 of the wheel disc rim 155 with a thermal spray gun 85, shown in phantom in FIG. 14. In the preferred embodiment, a ferrous powder is supplied to the thermal spray gun 85 for spraying to assure that the weld anchor 160 is compatible for welding the wheel disc 150 to a steel wheel rim. The thermal spray gun 85 can be held stationary while the wheel disc 150 is rotated about its axis to form the weld anchor 160.

A fragmentary sectional view of an assembled full face vehicle wheel 165, which includes the stamped wheel disc 150 and a partial wheel rim 166, is show in FIG. 15. In the preferred embodiment, the partial wheel rim 166 is formed from steel stock by a conventional process, such as rolling or spinning. The partial wheel rim 166 includes an outboard tire bead seat 167 which has a radially outward directed end terminating in an annular shaped outer edge 168. The wheel rim 166 further includes a drop well 169. The outboard tire bead seat 167 is contiguous with an annular drop well 169. The drop well 169 extends axially to an annular inboard tire bead seat 171. A ring

shaped inboard tire bead retaining flange 172 is formed on the inboard end of the inboard tire bead seat 171.

To assemble the vehicle wheel 165, the wheel rim 166 is positioned coaxially with the full face wheel disc 150 with the inboard tire bead retaining flange 172 parallel to the outboard tire bead retaining flange 157 and the wheel rim outer edge 168 abutting the weld anchor 160. The wheel rim 166 is secured to the wheel disc 150 with a single continuous circumferential butt weld 175 formed between the wheel rim outer edge 168 and the weld anchor 160. Alternately, a filler weld can be used to secure the wheel disc 150 to the wheel rim 166. It may desirable to grind or machine the weld 175 flush with the outer surface of the tire bead seat 167, however this step is optional. The weld 175 must be air tight to prevent air leakage when a tire is mounted upon the assembled wheel 165.

As in the previously described embodiments, it will be appreciated that the wheel rim 166 also can be formed from a light weight metal or alloy thereof which is dissimilar to the metal used to form the wheel disc 150. Additionally, while the invention has been illustrated with the weld anchor 160 formed on the wheel disc 150, the weld anchor can, as an alternative, be formed upon the wheel rim 166. For example, if the wheel disc 150 is formed from an aluminum alloy and the wheel rim from steel, a layer of aluminum or aluminum alloy can be sprayed onto the wheel rim outer edge 168 to form a weld anchor (not shown). The sprayed aluminum weld anchor would adhere to the steel wheel rim 166 and provide a compatible surface to which the wheel disc 150 can be welded. It will be appreciated that, while the method for welding dissimilar metals has been described above for fabricating wheels, the method can be used to weld together any two components formed from dissimilar metals. To apply the method, a layer of metal compatible with one of the components would be thermally sprayed onto a cleaned portion of the surface of the other component to form a weld anchor. The second component would then be welded to the weld anchor.

As an alternate to welding the wheel disc to the wheel rim during fabrication of the above described bimetal wheels, the wheel disc can be brazed to the wheel rim. As before, the portion of the wheel rim surface that is to contact the wheel disc is cleaned of any dirt, oil and oxides. A layer of nonferrous filler metal which is compatible with both the metals used to form the wheel disc and wheel rim is thermally sprayed onto the cleaned portion of

the wheel rim surface. The particular filler metal is selected depending upon the metals used to form the wheel disc and rim. For example, a copper- zirconium alloy or an aluminum alloy can be used as the filler metal to braze an aluminum wheel disc to a steel wheel rim. As described above, the thermal spraying causes the filler metal to bond to the wheel rim surface. A portion of the surface of the wheel disc is cleaned of any dirt, oil and oxides. The cleaned surfaces of the wheel disc and rim can be coated with a flux, such as borax, to prevent formation of oxides during the brazing process. The wheel disc is positioned concentric with the wheel rim and with the cleaned portion of the wheel disc surface contacting the layer of filler metal to form a wheel assembly. For a full face wheel disc, the outboard tire bead retaining flange on the wheel disc is positioned parallel to the inboard tire bead retaining flange on the wheel rim. The wheel assembly is heated to a brazing temperature at which the filler metal melts, but which is below the melting temperatures of the metals forming the wheel disc and rim. The heating is typically done in a furnace with a brazing temperature in excess of 800°F. (427°C). The melted filler metal forms a bond between the wheel disc and the wheel rim.

In the preferred embodiment, the wheel disc surface which is to be brazed is fitted closely to the corresponding wheel rim surface. For a bimetal wheel having the wheel disc disposed within the wheel rim, as illustrated in FIGS. 9 and 1 1, a close fit can be obtained by heating the wheel rim to expand the πm before inserting the wheel disc. The wheel disc is then inserted and the wheel rim cooled. The wheel rim contracts upon cooling to form a close fit with the filler metal clamped between the wheel rim surface and the wheel disc assure a strong brazed joint.

For bimetal wheels having a full face wheel disc joined to a partial wheel rim, as illustrated in FIGS. 13 and 15, the wheel disc and wheel rim can be mounted in a jig (not shown) prior to brazing. The jig includes means for clamping the disc and rim closely together such that the wheel disc fully contacts the layer of filler metal. The jig also maintains the wheel disc concentric with the wheel rim and the outboard and inboard tire bead retaining flanges parallel to each other. The jig and wheel assembly are heated to braze the wheel disc to the wheel rim. While brazing has been described above with the filler metal being deposited on a surface of the wheel rim, it will be appreciated that the filler metal also can be deposited with a thermal spray gun on a surface of the

wheel disc or on both the wheel rim and the wheel disc. It also will be appreciated that, while the method for brazing dissimilar metals has been described above for fabricating wheels, the method can be used to braze together any two components formed from dissimilar metals. To apply the method, a layer of filler metal compatible with both of the components is thermally sprayed onto a cleaned portion of the surface of one of the components. A portion of the surface of the other component is cleaned and positioned contacting the layer of filler metal. The two components are heated sufficiently to melt the filler metal. Upon cooling, a brazed joint is formed between the two components.

The present invention also contemplates thermally depositing a layer of metal onto a portion of the surface of a wheel rim. A wheel disc would then be cast or forged onto the wheel rim with the wheel disc covering a portion of the sprayed metal layer. The wheel rim and wheel disc would be formed from dissimilar metals. As described above, the metal sprayed onto the wheel rim would be selected to be compatible with the metal used to form the wheel disc. Accordingly, the wheel rim would be secured fused to the metal thermally deposited metal layer.

A fragmentary sectional view of a bimetal vehicle wheel 180 which is formed by the casting process described above is shown in FIG. 16. The wheel 180 includes a full face wheel disc 181 which, in the preferred embodiment, is formed from a light weight metal or alloy thereof by a conventional casting or forging process. The wheel disc 181 includes a center hub 182 having a pilot hole 182 and a plurality of wheel stud holes 184, one of which is shown, formed therethrough. A plurality of spokes 185, one of which is shown, extend radially from the hub 182 to an annular wheel disc rim 186. The wheel disc rim 186 includes an outboard tire bead retaining flange 187 which is formed adjacent to an outboard tire bead seat 188. The tire bead seat 188 extends axially to a drop well wall 189 and an annular portion of a drop well 190. The drop wheel portion 190 extends in an inward axial direction from the wheel disc rim 186.

The wheel 180 also includes a partial wheel rim 191 which, in the preferred embodiment, is formed from steel by a conventional process, such as described above. It will be appreciated, however, that other metals, which are different from the metal used for the wheel disc 181, can be used to form the wheel rim 191. The outboard end of the wheel rim 191 forms a portion of a drop well 192. The drop well 192 has inner and outer surfaces 193 and 194

and terminates in an annular shaped edge 195. As illustrated in FIG. 16, the outboard portion of the rim drop well 192 includes a surface layer 196 of a metal. The metal used to form the metal layer 196 is selected to be compatible for forming a bond with the metal of the wheel disc 181. For example, if the wheel disc 181 is aluminum, the metal layer 196 is formed from aluminum or an alloy of aluminum. The metal layer 196 extends axially from the rim edge 195 across a portion of the inner and outer surfaces 193 and 194 of the rim drop well 192. The outboard end of the rim drop well 192 extends into and is secured to the wheel disc drop well 190. The wheel rim 191 also includes an annular leg portion 197, an inboard tire bead seat 198 and an inboard tire bead retaining flange 199.

The method used to fabricate the wheel 180 is illustrated in the flow chart shown in FIG. 17. In functional block 200, a partial wheel rim without the metal layer 196 is provided. The outboard end portion of the wheel rim is prepared, in functional block 201, for the thermal deposition of the metal layer 196 by cleaning the surfaces to be covered in the manner described above. Metal compatible with the metal forming the wheel disc 181 is thermally sprayed onto the cleaned inner and outer surfaces 193 and 194 in functional block 202 to form the metal layer 196. As described above, the thermal spray process bonds the sprayed metal securely to the surface of the wheel rim. In the preferred embodiment, an arc plasma spray gun is used to deposit the metal, however, it will be appreciated that other types of thermal spray guns can be used. Application of the metal layer 196 to the wheel rim produces the wheel rim 191 illustrated in FIG. 16. While the metal layer 196 has been described as being formed on both the inner and outer surfaces 193 and 194 of the rim drop well 192, it will be appreciated that the metal layer 196 also can be formed on only one of the surfaces 193 and 194.

In functional block 203, the wheel rim 191 is positioned relative to a multi-piece wheel disc mold 205, as illustrated in the sectional view of the mold 205 and wheel rim 191 shown in FIG. 18. The wheel disk mold 205 includes a bottom core 206 which supports a pair of retractable side cores 207 and 208. An axially retractable top core 209 is disposed between the side cores 207 and 208. When the mold 205 is closed, as illustrated in FIG. 18, an annular opening 210 is formed between the side cores 207 and 208 and the top core 209 and a mold cavity 21 1 is defined for casting the full face wheel disc 181. The mold cavity 21 1 includes an annular rim portion 212 which corresponds to the wheel disc rim 186. The cavity rim portion 212 includes

an annular cavity 213 extending axially therefrom which corresponds to the wheel disc drop well portion 190.

To position the wheel rim 191 relative to the mold 205, the side cores 207 and 208 and the top core 209 are retracted. The wheel rim 191 is then positioned with the drop well 192 extending over the outer circumference of the top core 209. The side cores 207 and 208 are extended towards the top core 209, clamping the wheel rim 191 in position on the top core 209. The rim drop well 192 forms a seal between the side cores 207 and 208 and the top core 209. The top core 209 and side cores 207 and 208 are extended towards the bottom core 206 to close the mold 209. When the mold 205 is closed, as shown in FIG. 18, the rim drop well 192 extends through the annular opening 210 and the end portion of the wheel rim 191, which includes the metal coating 196, extends into the annular cavity 213. The wheel rim 191 is positioned coaxially with the mold cavity 21 1 and with the inboard tire bead retaining flange 199 parallel to the die cavity surface that defines the outboard tire bead retaining flange.

In functional block 215, molten metal is introduced to the mold cavity 21 1 through a sprue (not shown) to cast the wheel disc 181. The molten metal fills the annular mold cavity portions 212 and 213, covering and partially melting the metal layer 196. As the molten metal cools to form the wheel disc 181, the wheel disc drop well portion 190 is physically bonded to the metal layer 196 on the wheel rim 191, securely attaching the wheel rim 1 1 to the wheel disc 181. The metal in the wheel disc drop well portion 190 contracts as it cools, forming an air tight seal between the wheel rim 191 and the wheel disc 181.

After the wheel disc 181 has cooled sufficiently, the top and side cores 209, 207 and 208 are retracted allowing removal of the complete wheel 180 from the bottom core 206, as indicated in functional block 216 in FIG. 17. In functional block 217. conventional finishing operations are applied to the wheel 180 as needed. Such operations can include machining the wheel disc 181 to final shape and drilling the wheel stud holes 184 through the wheel disc hub 182. Additionally, one or more of the wheel surface finishing operations described above can be applied to the wheel 180.

As indicated above, the wheel 180 also can be formed with a forged wheel disc 181. The forging process is illustrated in the flow chart shown in FIG. 19. The initial three steps of the process are the same as described above for the cast wheel disc. A partial wheel rim is provided in functional

block 220 and prepared by cleaning the outboard portion of the drop well in functional block 221. In functional block 222. metal compatible with the metal used to form the wheel disc 181 is thermally sprayed onto the outboard portion of the wheel rim to form the metal layer 196. In functional block 223, the prepared wheel rim 191 is mounted upon a set of wheel disc dies 225, as shown in FIG. 20. The die set 225 includes a lower die 226 and a multi-piece upper die 227. The upper die 227 is axially movable relative to the lower die 226 between closed and open positions by a conventional mechanism (not shown). In the closed position, the upper die 227 extends into and cooperates with the lower die 226 to define a die cavity 228, as illustrated in FIG. 20. The die cavity 228 has an annular rim portion 229 which corresponds to the wheel disc rim 186. The cavity rim portion 229 includes an annular cavity 230 extending axially therefrom which corresponds to the wheel disc drop well portion 190. In the open position, the upper die 227 is completely withdrawn from the lower die 226.

The upper die 227 includes a center element 231 which is disposed between a pair of movable side elements 232 and 233. When the upper die 227 is in the closed position, as shown in FIG. 20. the side elements 232 and 233 are extended towards the center element 23 1. defining an annular opening 234 therebetween. When the upper die 227 is in the open position, the side elements 232 and 233 can be retracted from the center element 231. For clarity, the mechanism for extending and retracting the side elements 232 and 233 relative to the center element 231 has been omitted from FIG. 20.

To mount the wheel rim 191 upon the upper die 227, the upper die 227 is withdrawn from the lower die 226 and the side elements 232 and 233 retracted from the center element 231. The wheel rim 191 is then positioned with the drop well 192 extending over the outer circumference of the center element 231. The side elements 232 and 233 are extended towards the center element 231, clamping the wheel rim 191 in position on the upper die 227. The rim drop well 192 forms a seal between the side elements 232 and 233 and the center element 231. When the upper die 227 is closed, as shown in FIG. 20, the rim drop well 192 extends through the annular opening 234 and the end portion of the wheel rim 191. which includes the metal coating 196, extends into the cavity annular portion 230. The wheel rim 191 is positioned coaxially with the die cavity 228 and with the inboard tire bead retaining flange 199 parallel to the die cavity surface that defines the outboard tire bead retaining flange.

After the wheel rim 191 is mounted on the upper die 227, the dies are ready for forging the wheel disc 181, as indicated in functional block 235 in FIG. 19. A conventional forging process, such as squeeze forging is used. The squeeze forging process includes heating a disk shaped billet of metal ( ^' not shown) to a temperature that is slightly less than the melting temperature of the metal billet. The heated billet is placed between the upper and lower dies 226 and 227 and the upper die 227 is pressed axially into the lower die 226. As the dies are pressed together, the metal billet is squeezed into the die cavit 228, filling the die cavity annular portions 229 and 230. The heated metal flows over the end portion of the drop well 192 and into contact with the metal layer 196. The metal is sufficiently hot to partially melt the layer 196. As the molten metal cools to form the wheel disc 181, the wheel disc drop well portion 190 is physically bonded to the metal layer 196 on the wheel rim 191, securely attaching the wheel rim 191 to the wheel disc 181. The metal in the wheel disc drop well 190 contracts as it cools, forming an air tight seal between the wheel rim 191 and the wheel disc 181.

After the wheel disc 181 has cooled sufficiently, the upper die 227 is moved to the open position, withdrawing the wheel 180 from the lower die 226. The side elements 232 and 233 are retracted from the center element 231. allowing removal of the wheel 180 therefrom, as indicated in functional block 236 in FIG. 19. In functional block 237, finishing operations are applied to the wheel 180 as needed. For example, such operations can include machining the wheel disc to final shape and drilling the wheel stud holes 184 through the wheel disc hub 182. Additionally, one or more of the wheel surface finishing operations described above can be applied to the wheel 180.

A fragmentary sectional view of an alternate embodiment of a bimetal full face vehicle wheel 240 is shown in FIG. 21. Portions of the wheel 240 which are identical to corresponding portions of the previously described wheel 180 are indicated by the same numerical designator. The wheel 240 includes a wheel disc 181 which is formed by a conventional method, such as casting or forging, on the outboard end of a partial wheel rim 241, as described above. The outboard end of the wheel rim 241 includes a portion of a drop well 242. The drop well 242 includes a radial flange 243, which is shown in FIG. 21 at the axial outboard end of the drop well 242 extending in a radially outward direction. The flange 243 anchors the outboard end of the wheel rim 241 in the drop well portion 190 of the wheel disc rim 186. It will

be appreciated that while the flange 243 is shown extending in an outward radial direction, the flange can also be formed extending in an inward radial direction. Similarly, the flange 243 need not be formed on the axial end of the wheel rim 241. but can be formed on an intermediate portion of the drop well 242. Metal compatible with the metal used to form the wheel disc 181 is thermally sprayed over the flange 243 and the end portion of the drop well 242 to form a metal layer 244. As described above, when the wheel disc 181 is formed on the end of the wheel rim 241, the coating 244 bonds to the wheel disc 181 to form a secure air-tight seal between the wheel rim 241 and the wheel disc 181.

A fragmentary sectional view of another bimetal full face vehicle wheel 250 fabricated in accordance with the invention is shown in FIG. 22. The wheel 250 includes a partial wheel rim 251 and a full face wheel disc 252. The wheel rim 251 has an outboard end formed as an outboard tire bead seat 253. The outboard tire bead seat 253 is connected by a drop well wall 254 to a drop well 255. In the preferred embodiment, the wheel rim 251 is formed from steel by a conventional process, as described above. As also described above, metal compatible with the metal used to form the wheel disc 252 is thermally sprayed onto the outboard end of the wheel rim 251 to form a metal layer 256. .As shown in FIG. 22, the metal layer 256 extends axially inward from the outboard end of the wheel rim 251 over a portion of both the inner and outer surfaces of the tire bead seat 253. While the metal layer 256 is shown on both the inner and outer surfaces of the bead seat 253, it will be appreciated that the metal layer 256 also can be formed on only the inner surface. The thermal spray process provides a strong bond between the metal layer 256 and the wheel rim 251.

The full face wheel disc 252 includes a center hub 260 connected by a plurality of radial spokes 261. one of which is shown, to an annular wheel disc rim 262. The wheel disc rim 262 includes an outboard tire bead retaining flange 263 which defines a radial inboard surface 264. The radial surface 264 extends inwardly to an annular shoulder 265 which extends axially therefrom.

The wheel disc 252 is formed onto the outboard end of the partial wheel rim 251 by a conventional process, such as casting or forging, as described above. During the wheel disc forming process, the wheel disc rim shoulder 264 is formed in supporting contact with the inside surface of the wheel rim outboard tire bead seat 256. Furthermore, the heated metal forming the wheel disc 252 bonds to the metal coating 256 on the wheel rim

bead seat 253 to form a secure and air-tight bond between the wheel rim 251 and the wheel disc 252.

A fragmentary sectional view of an another alternate embodiment of a bimetal full face vehicle wheel 270 is shown in FIG. 23. Portions of the wheel 270 which are identical to corresponding portions of the previously described wheel 250 are indicated by the same numerical designator. The wheel 270 includes a partial wheel rim 271 and a full face wheel disc 252. The wheel rim 271 has an outboard end formed as an outboard tire bead seat 272. The outboard tire bead seat 272 includes a radial flange 273, which is shown in FIG. 23 at the axial outboard end thereof extending in a radially inward direction. The flange 273 anchors the outboard end of the wheel rim 271 in the wheel disc rim 262. It will be appreciated that, while the flange is shown formed on the axial end of the wheel rim 271, it also can be formed on an intermediate portion of the tire bead seat 272. Similarly, the flange can be formed extending in an outward radial direction. Metal compatible with the metal used to form the wheel disc 252 is thermally sprayed over the flange 273 and the inner and outer surfaces of the tire bead seat 272 to form a metal layer 275. While the metal layer 275 is shown on both the inner and outer surfaces of the bead seat 272, it will be appreciated that the metal layer 275 also can be formed on only the inner surface. The thermal spray process provides a strong bond between the metal layer 275 and the wheel rim 271. As described above, when the wheel disc 252 is formed on the outboard end of the wheel rim 271, the metal layer 275 bonds to the wheel disc 252 to form a secure air-tight bond between the wheel rim 271 and the wheel disc 252. It will be appreciated that, while the method for attaching dissimilar metals components has been described above for fabricating vehicle wheels, the method can be used to join together any two components formed from dissimilar metals. To apply the method, metal compatible with one of the components would be thermally sprayed onto a cleaned portion of the surface of the other component to form a metal layer. The second component would then be cast or forged over the metal layer.

Another embodiment of the invention contemplates thermally depositing a layer of material on a portion of the wheel rim surface to seal the wheel rim. This embodiment of the invention is illustrated in FIG. 24, which shows a fragmentary sectional view of a typical vehicle wheel 280. The wheel 280 has a rim 281 that includes an outboard tire bead retaining flange 282 which is adjacent to an outboard tire bead seat 283. The outboard tire

bead seat 283 is connected by a radial drop well wall 284 to an annular drop well 285. The drop well 285 is adjacent to an annular leg portion 286 of the rim 281. The inboard end of the leg portion 286 is adjacent to an inboard tire bead seat 287, which terminates in an inboard tire bead retaining flange 288. -A wheel disc 290 is formed across the outboard end of the wheel rim 281. The wheel disc 290 includes a wheel hub 291 having a central pilot hole 292 and a plurality of wheel lug holes 293 (one shown) formed therethrough. A plurality of spokes 294 (one shown) extend radially from the hub 291 to the wheel rim 281. Conventional methods for forming vehicle wheels can cause the drop well 285 to be thinner than other portions of the wheel rim 281. This can cause, depending upon the porosity of the metal used to form the wheel, a slow leakage of air through the drop well 285. The air leakage can result in deflation of a tire mounted upon the wheel rim 281. To improve air retention of the wheel rim 281, a layer of metal is thermally deposited over the outer surface of the drop well 285. The outer surface of the drop well 285 is prepared by removing any dirt, oil or oxides therefrom. Cleaning can include conventional steps, such as immersion of the wheel 280 in a solvent to remove dirt and oil, immersion in a chemical bath to remove oxides and rinsing to remove any solvent and chemicals. The rinse can be by immersion in a water bath or by flushing with a water jet.

A thermal spray gun 300, shown in phantom, deposits an annular layer of metal 301 over the prepared drop well surface. In the preferred embodiment, an arc plasma spray gun, as illustrated in FIG. 3, is used to form the metal layer 301; however, other types of thermal spray guns can be used. The spray gun 300 can be traversed axially as the wheel 280 is rotated about its axis to deposit a uniform metal layer 301. As described above, the density of the thermally deposited metal layer 301 is greater than the density of the metal forming the wheel rim 281. Accordingly, the drop well layer 301 is less porous than the wheel rim metal, sealing the drop well 285 and reducing leakage of tire inflation air therethrough.

While the metal layer 301 has been described as being formed on the outer surface of the drop well 285, the layer 301 also can be formed on the inner surface thereof. Furthermore, while FIG. 24 shows the metal layer 301 extending across only the drop well 285, it will be appreciated that the metal layer 301 also can extend axially across the leg portion 286 of the wheel rim 281.

In the preferred embodiment, the same metal that is used to form the wheel rim 281 is used to form the metal layer 301. However, it will be appreciated that because of the bonding nature of the thermal spray process, other metals and non-metallic materials also can be used to form the layer 301 5 over the drop well surface.

.An alternate embodiment of the invention contemplates thermally depositing a layer of material over the tire bead seats. This alternate embodiment is illustrated in FIG. 25 which includes a fragmentary sectional view of a wheel 303. Portions of the wheel 303 which are identical to 0 corresponding portions of the wheel 280 are identified by the same numerical indicators used in FIG. 24. The wheel 303 includes an annular wheel rim 304 having outboard and inboard tire bead seats 283 and 287 formed therein.

The outer surfaces of the tire bead seats 283 and 287 are prepared by removing any dirt, oil or oxides therefrom. The thermal spray gun 300, 5 shown in phantom in FIG. 25, deposits annular metal layers 305 and 306 on the outer surface of the tire bead seats 283 and 287. The outboard tire bead sear metal layer 305 is deposited with the thermal spray gun 300 in position "A". The spray gun 300 can be axially traversed about position "A" and the wheel 304 rotated about its axis while the metal layer 305 is deposited. After 0 completing the outboard bead seat metal layer 305, the spray gun 300 is axially moved to the position labeled "B" to deposit the inboard bead seat metal layer 306. Alternately, two thermal spray guns (not shown) can be used to deposit both metal layers 305 and 306 simultaneously.

In the preferred embodiment, the thermal spray gun 300 is an arc : plasma gun; however, other types of thermal spray guns can be used to deposit the metal. Also in the preferred embodiment, the same metal used to form the wheel rim 304 is used to form the metal layers 305 and 306. However, it will be appreciated that because of the bonding nature of the thermal spray process, other metals and non-metallic materials can be used to 0 form the layers 305 and 306.

The metal layers 305 and 306 are not polished, but are left as sprayed. Accordingly, the surface of the metal layers 305 and 306 have a higher coefficient of friction than the surfaces of the adjoining portions of the wheel rim 281. .As a result, the bead seats 283 and 287 have an enhanced capability to prevent tire beads from rotating relative to the wheel rim 281 when mounted thereon.

It will be further appreciated that, while the invention has been described above as forming annular layers of metal on the drop well surface and the tire bead seat surfaces, it is also possible to spray a layer of metal or non-metallic material across the entire outer surface of the wheel rim 281. The resulting layer of material would extend axially from the outboard tire bead retaining flange 282 to the inboard tire bead retaining flange 288.

.Another embodiment of the invention contemplates thermally depositing a protective layer over a wheel mounting surface. This embodiment is illustrated in FIG. 26. which includes an enlarged fragmentary sectional view of a wheel 307 having a central wheel hub 308. Portions of the wheel hub 308 which are identical to corresponding portions of the wheel hub 291 in FIG. 24 are identified by the same numerical indicators. The inboard side of the wheel hub 308 includes a hub mounting surface 310. The mounting surface 310 is typically machined flat to assure optimal support of the wheel 307 after installation upon a vehicle (not shown). When the wheel 307 is mounted upon a vehicle, the mounting surface 3 10 is often positioned adjacent to and contacting a cast iron brake drum (not shown). The cast iron can react chemically with the metal forming the wheel 307. especially when the wheel is subject to high humidity or precipitation. The chemical reaction can result in corrosion of the wheel mounting surface 310.

Before depositing a protective layer over the wheel mounting surface 310, the mounting surface 310 is prepared by removing any dirt, oil or oxides. The thermal spray gun 300 then deposits a protective layer 31 1 of chemically inert material, such as a ceramic, over the mounting surface 310. The protective layer 31 1 seals the mounting surface 310, preventing corrosion from forming thereon. The protective layer 31 1 is not polished, but is left as sprayed. Accordingly, the surface of the protective layer 31 1 has a higher coefficient of friction than the mounting surface 310. As described above, an arc plasma spray gun is used in the preferred embodiment to form the protective layer 31 1, however, other types of thermal spray guns can be used. The spray gun 300 can be traversed radially over the mounting surface 310 while the wheel 307 is rotated about its axis to deposit a uniform protective iayer 311.

An additional embodiment of the invention is illustrated in FIG. 27, which contemplates thermally depositing a layer of material about the outboard end of the wheel lug holes 293. FIG. 27 shows an enlarged fragmentary sectional view of a wheel 312 that includes a central wheel hub

313. Portions of the wheel hub 313 which are identical to corresponding portions of the wheel hub 291 in FIG. 24 are identified by the same numerical indicators. As described above, the wheel hub 313 includes wheel lug holes 293. The outboard end of the wheel lug holes 293 can include a cylindrical counterbore 315 for seating a wheel lug nut (not shown). The counterbore includes a bottom surface 316 against which an end of the wheel lug nut is seated. Additionally, an outboard portion 317 of the wheel lug hole 293 can be tapered to assist centering of the wheel hub 313 upon the vehicle mounting surface. When the wheel hub 313 is formed from aluminum or another relatively soft metal, it is known to include a bushing (not shown) formed from a ferrous material in the counterbore 315. The bushing covers the counterbore bottom surface 316 and provides a bearing surface for the wheel lug nut. The bearing surface distributes the torquing force applied to the wheel lug nut. This reduces the possibility of deforming the wheel hub 313 when the wheel lug nuts are torqued.

This embodiment of the invention contemplates replacing the counterbore bushing in each of the lug hole counterbores 315 with a thermally deposited reinforcing layer 318. Accordingly, the counterbore bottom surface 316 and the surface of the lug hole tapered portion 317 are prepared by removing any dirt, oil or oxides therefrom. Then, as shown in FIG. 27, the reinforcing layer 318 is deposited with the thermal spray gun 300 onto the counterbore bottom surface 316. In the preferred embodiment, the thermal spray gun 300 is an arc plasma gun, however other types of thermal spray guns can be used to deposit the layer 318. The material used to form the layer 318 can be a ceramic or a hard metal, such as stainless steel or nickel. .A portion of the reinforcing layer 318 extends axially into the lug hole 293 and over the surface of the tapered portion 317. It will be appreciated, however, that the invention can be practiced with the reinforcing layer 318 covering only the counterbore bottom surface 316. The reinforcing layer 318 is not polished, but forms a surface having a greater the coefficient of friction than the counterbore bottom surface 316.

The thermal spay gun 300 can be mounted upon a robotic arm and indexed between the lug holes 293 to deposit a reinforcing layer 318 in each lug hole 293. Alternately, a plurality of thermal spray guns can be mounted upon a mechanism (not shown) that would simultaneously deposit the layers 318 in all the wheel lug holes 293.

A sectional view of an alternate embodiment 320 of the arc plasma spray gun which is capable of thermally depositing a mixture of two materials is shown in FIG. 28. As will be explained below, the spray gun 320 can be used to thermally deposit a metal matrix composite layer to reinforce a portion of a vehicle wheel. The components of the spray gun 320 which are the same as components of the arc plasma gun 30 described above are labeled with the same numerical designators. The spray gun 320 includes a first material inlet port 321 which communicates with the nozzle 33 downstream form the arc chamber 32. The first material inlet port 321 is connected to a pressurized supply of a powdered metal (not shown), such as aluminum, magnesium and titanium, or alloys thereof. The spray gun 320 also includes a second material inlet port 322 which also communicates with the nozzle 33 downstream from the arc chamber 32. The second material inlet port 322 is connected to a pressurized supply of a nonmetallic reinforcing material (not shown), such as silicon carbide, alumina, silica and graphite. The reinforcing material can be in the form of particulates, small fibers or whiskers. While the second inlet port 322 is shown downstream from the first inlet port 321 in FIG. 28, it will be appreciated that the positions thereof can be reversed or that the inlet ports 321 and 322 can be located opposite one another. During operation of the spray gun 320, a DC arc (not shown) is struck between the spray gun electrodes 31 and 34. As described above, the high arc temperature causes a rapid expansion of the inert gas mixture supplied through the gas inlet port 36 to form a plume 40 of ionized gases. The plume of ionized gases 40 is discharged through the nozzle 33. The powdered metal, which is entrained in an inert carrier gas, such as helium, is injected under pressure through the first material inlet port 321 into the plasma plume 40 in the nozzle 33. The powdered metal includes very small particles which the temperature of the plasma plume 40 melts to form small droplets of molten metal. Simultaneously with the injection of the powered metal, the reinforcing material, which is entrained in an inert carrier gas. such as helium, is injected under pressure through the second material inlet port 322 into the plasma plume 40 in the nozzle 33. The particles of reinforcing material are mixed with the molten metal droplets in the plasma plume 40. The mixture of reinforcing material particles and molten metal droplets are carried by the plasma plume 40. The plasma plume 40 is directed at a surface 324 of a metal component 325, such as a vehicle wheel, which is shown in fragmentary section in FIG. 28. The spray gun 320 deposits a layer 326 of

the reinforcing material particles/molten metal mixture on the component surface 324.

The powdered metal supplied to the first material port 321 is similar to the metal used to form the component 325. For example, powdered aluminum could be supplied for spraying onto an aluminum alloy component. Accordingly, the initial molten metal droplets deposited upon the surface 324 fuse thereto, binding the layer 326 securely to the surface 324. Upon cooling, the sprayed metal combines with the reinforcing material to form a metal matrix composite (MMC) reinforcing layer which covers a portion of the component surface 324. It will be appreciated that the aluminum and alumina are used in the above example to illustrate the invention. As indicated above, any of a number of conventional reinforcing materials can be combined with a number of powered metals to form the MMC.

It will be appreciated that other commercially available thermal spraying means can be used to form the reinforcing MMC layer 326. For example, a wire or rod formed from the metal can be fed into the plasma plume of an electric arc gun or a high velocity oxygen hydrocarbon fuel spray gun could be used to spray the metal droplets onto the metal component 325. In both cases, the reinforcing material would be would be entrained in an inert gas and injected under pressure into the nozzle of the spray gun through a material inlet port. Additionally, the arc plasma spray gun 30 shown in FIG. 3 can be used to deposit the MMC layer by supplying a mixture of the powdered metal and reinforcing material to the material inlet port 39.

As shown in FIG. 29, the spray gun 320 can be positioned inside a wheel 330 to deposit a MMC reinforcing layer 331 on an inner surface thereof. Portions of the wheel 330 which are identical to corresponding portions of the wheel 280 are identified by the same numerical indicators used in FIG. 22. The spray gun 320 and/or the wheel 330 can be rotated about the wheel axis to assure formation of a uniform MMC reinforcing layer 331. As shown in FIG. 29, the MMC reinforcing layer 331 extends from a portion of the wheel hub 291, across the inside surface of the wheel spokes 294 and onto a portion of the inside surface of the wheel rim 281. The MMC reinforcing layer strengthens the wheel spokes 294 (one shown), allowing use of a smaller spoke cross sectional area. Additionally, the MMC reinforcing layer 331 can be extended in an axial direction across the inside surface of the wheel rim 281. This can allow use of a thinner wheel rim 281. Alternately,

the MMC reinforcing layer 331 can be applied only to the inside surface of the wheel rim 281 or to other sleeted inner or outer surfaces of the wheel 331.

In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.