This invention was made with government support under Contract No. W-7405- ENG-36 awarded by the U.S. Department of Energy. The government has certain rights in the invention.

BACKGROUND ART Rods and wire have been made by melting the metal or alloy from which the wire or rod is to be formed, casting an ingot from the molten metal or alloy, processing the ingot in a rolling mill, and drawing the rolled metal or alloy through a forming die into the desired rod or wire diameter. Extrusion processes for making wire are also available.

These methods generally require use of heavy equipment and tools, heat treatments for casting, forging, drawing, or extruding or both, and annealing. The traditional methods also generally require many iterative sequences of steps to achieve the final diameters of wire or rod.

The types of material from which the rod or wire can be made by traditional multi-step processes are also limited to metals or alloys which can be plastically

deformed and extruded and economically processed by these methods. Brittle, low ductility materials do not easily lend themselves to deformation processing.

Expensive wire drawing dies are subject to abrasion in using traditional manufacturing methods to make wire of hard or abrasive materials.

Conventional processing of metals or alloys into wires or rods can result in contamination which can significantly affect the mechanical or metallurgical properties of the finished wires or rods.

There have been developed methods of making articles using metal powder melted by a laser beam, as disclosed in U.S. Patent No. 4,724,299. U.S. Patent No.

5,1 1 1,021 discloses addition of material to a surface using a laser beam and metal powder. Although these patents disclose cladding or encrusting existing surfaces on articles, they do not disclose formation of defined wires or rods.

U.S. Patent No. 4,743,733 discloses repair of an article by directing a laser beam and a stream of metal powder to a region of the article which needs repair.

These repair methods rely on support of the molten pool by a previously existing substrate of the article being repaired.

U.S. Patent No. 4,323,756 discloses a method for producing metallic articles from metal powders and substrates which become part of the articles. A focused energy beam is used to create a molten pool on a substrate and metal powder is supplied to a point outside of the area at which the beam impinges upon the substrate.

Movement of the substrate then carries the powder into the beam and molten pool, where it melts and mixes with the melted substrate material.

There is still a need for methods of making wire and rod which do not require extreme operating conditions, heavy equipment and large capital outlays. There is also a need for methods of making wire and rod in fewer processing steps. Methods and apparatuses are needed for making wire and rod from more different types of materials than can easily be processes in the traditional manufacturing methods and apparatuses. There is also a need for ways of reducing or eliminating contaminants in wire or rod products.

It is an object of this invention to provide a single-step method of making wire and rod.

It is another object of this invention to provide a method of making wire and rod from a larger variety of materials than the metals and alloys from which wire and rod are now made.

It is a further object of this invention to provide a method of making wire and rod from a broad selection of particulate materials.

It is still another object of this invention to provide a method of making wire and rod which reduces or eliminates contamination of the wire and rod articles.

It is yet another object of this invention to provide a laser deposition process for making wire and rod.

It is a still further object of this invention to provide a method of making wire and rod with specific properties such as microstructural or magnetic orientation.

Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by

practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

DISCLOSURE OF INVENTION To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, there has been invented a method of making elongated articles from materials in particulate form comprising: (a) defining the shape and dimensions of an article; (b) providing a means for introducing particulate material into a deposition zone; (c) creating a deposition path and control commands effective to form the article by deposition of molten material; (d) focusing a laser beam at a location within the deposition zone; (e) providing particulate material to the deposition zone; (f) forming a pool of molten material in the deposition zone by melting a portion of an article support and the particulate material by means of energy provided by the laser beam; (g) depositing molten material from the deposition zone on the article support at points along a first portion of the deposition path by moving the deposition zone along the deposition path, where the molten material solidifies after leaving the deposition zone, in order to form a portion of the article which is adjacent to the article support; (h) forming a pool of molten material in the deposition zone by melting a portion of the partially formed portion of article and the particulate material by means of energy provided by the laser beam; (i) depositing molten material from the deposition zone at points along a second portion of the deposition path by moving the deposition zone along the deposition path, where the molten material solidifies after leaving the deposition zone, in order to continue formation of the article; and

(j) controlling flow of particulate material into the deposition zone, energy density of the laser beam and focal position of laser beam by means of the control commands as deposition takes place.

Alternatively, instead of moving the deposition zone along a deposition path, as in steps (g) and (i), the deposition zone can be focused and held in constant position with the wire or rod being withdrawn from the deposition zone as it is formed. Provisions can be made for recycling any unused particulate material in the process.

In another embodiment, an apparatus for carrying out the process of this invention is provided. The inventive apparatus comprises: (a) a means for defining the shape and dimensions of an article, this means being capable of creating a deposition path and control commands effective to form an article by depositions of molten material; (b) a means for introducing particulate material into a deposition zone; (c) a laser positioned to focus a laser beam into the particulate material in the deposition zone; (d) a means for supporting and drawing the article away from the deposition zone; (e) a means for controlling flow of the particulate material, energy density of the laser beam, focal position of laser beam, and speed of withdrawal of the article being formed from the deposition zone by using the control commands.

Alternatively, instead of having a means to withdraw the article from the deposition zone, there is provided a means for moving the deposition zone along the deposition path away from the article being formed. Provisions can be made for recycling any unused particulate material in the process.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part of the specification, illustrate some of the embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: Figure 1 is a schematic representation of rod formation in accordance with the present invention wherein free standing rods of any diameter can be formed by any combination of x, y, z or rotary motion.

Figure 2 is a schematic representation of continuous processing of material and wire formation in accordance with the present invention.

Figure 3 is a schematic representation of a set up for making wire or rod from a three-component particle mixture.

Figures 4a, 4b, 4c and 4d show examples of some of the various deposition paths which can be used in the practice of the present invention to create the relative motion needed to form the cross sections of wire, rod or bar shapes.

Figure 5 shows a metallographic cross section of a nickel based alloy rod made using a layered deposition path.

Figures 6a and 6b show a metallographic cross section and longitudinal section of a fully dense titanium aluminum alloy rod made in accordance with the present invention.

Figure 7 shows thin wire segments made from 316 stainless steel, tungsten, nickel aluminide and molybdenum disilicide in accordance with the present invention.

Figure 8a is a flow chart of conventional wire manufacture compared with a flow chart (Figure 8b) of the invention method of wire manufacture.

Figures 9a, 9b and 9c show the powder used, microstructure as shown in a micrograph of a polished cross section and fracture surface, respectively, of wire made in accordance with the invention from 316 stainless steel.

Figures 10a, 10b and 10c show the powder used, microstructure as shown in a micrograph of a polished cross section, and fracture surface, respectively, of wire made in accordance with the invention from tungsten.

Figures 1 la, 1 lib and 1 1c show the powder used, microstructure as shown in a micrograph of a polished cross section, and fracture surface, respectively, of wire made in accordance with the invention from nickel aluminide.

Figures 12a, 12b and 12c show the powder used, microstructure as shown in a micrograph of a polished cross section, and fracture surface, respectively, of wire made in accordance with the invention from molybdenum disicilide.

BEST MODES FOR CARRYING OUT THE INVENTION It has been discovered that articles, particularly elongated articles in the form of wires or rods, can be produced by an additive directed light fabrication process.

An elongated article such as a wire or rod is constructed by melting and depositing particulate material into a deposition zone which has been designed to yield the desired article shape and dimensions. The article is withdrawn from the deposition zone as it is formed, thus enabling formation of the article in a continuous process.

The process of this invention can be carried out using laser light as the means for melting the particulate material. Suitable pulsed or continuous wave lasers include those which produce sufficient energy to melt the materials from which it is desired to form wire or rod. Suitable optics to achieve focus and energy densities to concentrate the energy required for melting of the selected materials are needed.

The directionality of the laser beam with respect to the deposit is guided by computerized numerical control (CNC) machine commands or electromechanical means to directly deposit particulate metal to form an accurately configured, fully dense metal article. No molds, patterns or masks are required, only the precise articulation of the laser and stream of particulate material in relation to the deposit to form the article. The articulation of a three-dimensional relative motion controls and configures the material deposition and resultant geometry of the articles being formed.

Once begun, the invention method can continuously process material without stopping, including the sectioning and packaging of the product.

An article support or substrate, generally a stub of wire or rod or other article having compatible geometry, made of a metallurgically compatible material, is mounted in a means for withdrawing the elongated formed article from the deposition zone. The article support is positioned so that the laser light strikes a trailing end of the article support as the first of the particulate material is deposited upon the trailing end of the article support as it melts.

The substrate or article support upon which the particulate material is deposited may be cry stallo graphically oriented such as when a single crystal is used for the article support. When a single oriented crystal is used as a support for the

invention method of making wire or rod, in combination with the unidirectional heat flow produced by the process and epitaxial grain growth of a preferred orientation in the wire or rod being produced can be accomplished. This embodiment of the invention can be used to make a solidified (fully dense) wire or rod product with unique metallographic properties.

Elongated articles having specific magnetic orientations can also be made using the invention method. To do this the substrate or article support upon which the particulate material is deposited is magnetically oriented such as when a magnet is used for the article support. When a magnetic material is used as a support for the invention method of making wire or rod, epitaxial grain growth of a preferred magnetic orientation in the wire or rod being produced can be accomplished.

Alternatively, the deposition zone can be exposed to a magnetic field produced independently of the article support. Exposure of the deposition zone to a magnetic field having a selected orientation can be used to produce epitaxial grain growth with desired magnetic orientations.

To start fabrication of an article, a small portion of the article support is melted by the laser beam to form a molten pool. If the molten zone is too large or too small, the stability and integrity of the process decreases. Therefore, the processing variables (such as powder flow, delivery gas flow, laser power, laser focus, and relative motion must be precisely controlled and are very important in producing rods or wires having uniform dimensions and composition.

At least one stream of solid particulate material, or powder, is supplied to the point where the laser light is focused. This generally done by means of gravity,

mechanical feed mechanism, an assist gas with an eductor, or a combination of any of these feed mechanisms. A key feature of the powder delivery mechanism is that rather than merely delivering particulate material to the focal zone of the laser, the powder delivery mechanism can deliver at least one focused stream of particulate material co-focally to the laser energy.

The particulate material is melted by heat generated when the laser light strikes the particles and by transfer of heat from the molten pool to the particulate material as the particulate material comes into contact with the molten pool.

After a small amount of material has been melted, the molten pool volume increases and begins to be enlarged by the introduction of more particulate material and laser energy. A continuous solid microstructure is achieved by maintaining a continuous solidification front when using a continuous wave laser or by remelting a portion of the previously deposited material and solidification when using a pulsed laser.

The space containing and surrounding the molten pool, the laser focal spot size, the "focal point" of the stream of particulate material, the focal point location of the laser beam, and that portion of the laser beam where energy density is great enough to melt the particulate material is termed the deposition zone.

As molten particulate material is deposited and cooled, a portion of the cooled, solidified particulate material can be re-melted by the impinging laser light and is mingled with the molten particulate material being newly formed. The method of this invention relies in part on precise focus of the stream of particulate material directly into the laser beam and molten pool which provides for both preheating of the

particulate material by the beam and melting of the particulate material by entry of the particulate material into the molten pool. Uniform deposition can best be achieved by having the laser energy and powder in co-focal positions.

The deposition rates can be precisely controlled to achieve cooling rates ranging from 10 K/sec to more than 105 K/sec. This broad range of deposition rates enables a wide range of deposit geometry and microstructures.

The motion command sequence of control moves the focal zone of the laser systematically relative to the length of the wire or rod to fuse metal powder particles that are delivered to the focal zone into solid metal and form the wire or rod continuously.

Alternatively, the laser and powder deposition devices can be held in constant position while the formed wire or rod is withdrawn from the deposition zone as deposits consisting of the particulate material are consolidated by melting and subsequently solidified due to loss of heat to the surroundings.

The focal point of the laser light can be moved about a path in accordance with computerized numerical control software. As an example, the focal point of the laser can be programmed to move along a helical path to produce a coil or spring geometry for continuous indefinite lengths or to increase the diameter of a rod.

However, the processes of this invention do not rely exclusively on a three- dimensional solid computer based model. The method of this invention also provides for the fabrication of wire or rod with a high directionally oriented microstructure due to the potential for microstructural growth under near unidirection heat flow and solidification conditions.

The invention method can be used to make discrete, single articles one at a time. Alternatively, the invention method can be used for producing continuous uninterrupted runs. For example, as deposited wire is formed continuously, it can be taken up onto spools positioned outside the processing chamber, without stopping or even slowing production between spools.

With reference to Figure 1, in one embodiment of the invention, a beam from an Nd:YAG laser 10 is delivered by means of a fiber optic 12 through a laser window 14, into a containment chamber 18, to a sealed boot 20 that holds a laser focusing head 22.

The means for withdrawing the focusing head 22 from the formed wire or rod and the articulation and relative x, y, z, or rotary motion of the deposition zone 28 can also be contained within the sealed containment chamber 18. Alternatively, the means for withdrawing the wire or rod from a deposition zone can be outside the sealed chamber.

The focused laser beam 24 enters the containment chamber 18 through a quartz laser window 14 in a nozzle 16 that also delivers the particulate material to the focal zone 30.

For many applications, the entire process takes place in an inert gas atmosphere in the sealed containment chamber 18 if that is made desirable by the properties of the material being processed. The sealed chamber atmosphere can be conditioned by a dry train 64 that reduces the oxygen content within the chamber to Sppm or less. Employment of a sealed chamber to control the atmosphere is useful when processing materials which would be reactive with oxygen or moisture in the air

or when oxygen or moisture could become unintentionally incorporated into the product. Relatively unreactive gases such as nitrogen or argon can be used. However, when processing less reactive materials such as precious metals or some steels. the invention can be practiced without use of a sealed chamber.

In the upper right of the schematic of Figure 1 is a powder mixing chamber 38.

The powder mixing chamber 38 can be evacuated and backfilled with inert gas. The powder feeder 32 entrains the particulate material in an inert gas stream that delivers the particulate material to the laser focus nozzle 16 and then to the focal zone 30.

Optionally a powder stream splitter 78 can be used to direct a plurality of powder streams into the deposition zone from a plurality of directions. The inert gas stream can be recycled from the containment chamber 18 back into the delivery gas supply 40 or back into the delivery gas supply 40 by way of a gas purifier, treatment unit or recycler 64.

A positioning controller 42 drives the "x", "y", and "z" tables, switches the laser shutter 44 and powder feeder 32 on and off, and controls various gas flows.

Examples of commercially available positioning controllers which can be used include, but are not limited to, AnoradTM and LaserdynJM controllers.

Still with reference to Figure 1, the deposition process is started by forming a molten pool on a support means 46 such as a short segment of wire or rod that can be cut off after deposition is complete. Typically the support is heated by the laser beam 24 without the powder feed turned on to preheat the support means 46 create melting, and promote better adhesion of the first fused powder volume. Particulate material is then formed into a conic particulate stream 26 and fed into the focal zone 30 and the

wire or rod is deposited continuously until the desired length of material is generated.

The particulate material melts and resolidifies as heat is removed by conduction through the base and by radiation from the deposition zone. Excess particulate material which does not reach the focal zone 30 of the laser beam accumulates at the base of the support means 46 and is collected by the powder collection recycler 60 for reuse. Alternatively, the particulate material can be recycled directly back to the powder mixing chamber 38 in a continuous loop process.

In a second embodiment of the invention a new means to continuously process wire, rod or other elongated commercial shapes is described. Unlike conventional continuous casting which relies on crucibles, rolls and molds to confine and shape the melt, the invention process can be used to manufacture wire or rod in a single continuous step.

This continuous processing embodiment of the invention method can be a containerless process achieving melting and forming of the shape without contacting other materials during formation of the wire or rod.. The shape is achieved and cooled prior to spooling, cutting or packaging into lengths or spool sizes specified by the customer.

A simplified continuous processing method in accordance with the invention, shown in Figure 2, uses a fixed laser beam 24 (without fiber optic delivery), a single axis of motion (z) without computerized numerical control, an inert but lower purity inert atmosphere containment chamber 18 and a feed through seal 54 for removal of material.

With reference to Figure 2, a laser 10 is positioned to focus through a laser window 14 into a laser focusing head 22 so as to project a laser beam 24 into a deposition zone 28. Simultaneously therewith, a relatively inert gas from a delivery gas supply 40 is used to direct particulate matter from a powder feeder 32 in a particulate stream 26 into the deposition zone 28. In the focal zone 30 in the deposition zone 28 the laser beam 24 melts the particulate matter and forms the elongated wire or rod 50 in the same manner described with reference to the first embodiment of the invention. A means 48 for withdrawing wire or rod is positioned below the deposition zone 28 so that the wire or rod product 50 is withdrawn from the deposition zone 28 as it is formed.

A redirecting roller 52 can be used to allow withdrawal of the formed wire or rod at an angle to the formation direction. A feed through seal 54 allows the formed wire or rod 50 to be pulled from within the containment chamber 18 onto a take-up spool 58. After the desired amount is wound onto the take-up spool 58, formed wire may be cut in a cut off location 56 allowed between the feed through seal and the take-up spool 58 and the new end started onto a new take-up spool.

Any unused particulate matter is caught in a powder collection recycler 60 and recycled through a powder recycling loop 62 back into the powder feeder 32.

Another embodiment of the invention is a method of continuously producing wire or rod having varying cross sections or of changing from one cross section or specific chemical composition to another without stopping the process to retool. For example, production of 0.045" wire can be seamlessly converted into production of 0.065" wire without stopping to change drawing dies or other equipment such as that

required by conventional processing. This is accomplished by changing parameters which affect the deposition rate, such as laser power, motion speed and powder flow rate. The powder composition can be altered or changed by adding or refilling a new type or grade of powder to the powder feed supply.

For example, three powder compositions can be fed sequentially or simultaneously and combined with the laser energy and inert gas, and focused into a deposition zone to produce a deposit. This deposit can be varied from one specific chemical composition to another during continuous production of the wire or rod by controlling the proportionate amount of each of the three powders going into the mixture.

With reference to Figure 3, three separate powder feeders 32 34 and 36 are filled with the selected particulate materials and adjusted to release the desired proportionate amounts by adjusting the rate of screw feeders and adjusting the delivery gas pressure for each of the three separate powder feeders. The three different feed materials from three separate powder feeders 32 34 and 36 are combined in a common powder mixing chamber 38. Relatively inert delivery gas from a delivery gas source 40 is used to carry the powder from an eductor which is fed by the common powder mixing chamber 38 to the delivery nozzle 16 in the form of a powder/inert gas mix.

The inert delivery gas also serves to protect the molten pool and provides cooling of the deposit. The inert delivery gas shields the deposition zone 28 from oxygen or contamination by other unwanted materials.

Manufacturing models (deposition paths) have been constructed for a number of different rod diameter, shapes and translated into motion system program code using a custom post processor specifically configured for a five-axis directed light fabrication system operated in accordance with the present invention. Figures 4a, 4b, 4c and 4d show four exemplary deposition paths for deposition of successively larger diameter wires, rods and bars.

Three-dimensional CAD/CAM models have been constructed using both Pro/ENGfNEER and ICEM software to create computerized numerical control files to design cross sections of articles which could be continuously formed by the process of this invention. Pro/ENGINEER software provides a highly integrated three- dimensional solid modeling environment which has been recently employed in the field of rapid prototyping. For example, Pro/ENGINEER software has been used by plastics manufacturers to describe surface features by triangulation. These triangulation files can be used to direct the formation of plastic shapes using commercially available plastic prototyping machines. ICEM has been used successfully to support three-dimensional CAD/CAM design needs and provides extensive CAM programming capabilities.

Post processors can also be constructed to translate manufacturing models or generic tool paths into multi-axis machine tool motion programs or machine-specific code for deposition of particulate materials into elongated articles having specialty- shaped diameters or circumferences in accordance with the present invention.

Process simulation can be performed to determine processing times and cooling rates (and thus resultant microstructure) for various processing conditions.

These simulations can be used to determine the effect of process variables such as deposition speed, focal zone size and successive pass overlap. Process simulations can also provide a means to analyze computational requirements such as computer processing times, file sizes and data transfer rates. Solidification models can be used to provide a means of predicting the microstructure of the deposited material and for selecting the desired microstructures.

Simulations are also useful for investigating and developing the CAM procedures necessary to generate wires or rods having surface features or diameter configurations of increasing complexity. Commands and routines specific to the directed light fabrication process of this invention can be integrated into the deposition path for additional control. Customization of the CAD/CAM interface and post-processing capability can be used to define and develop a software system specific to the directed light fabrication process as applied to continuous processing.

Materials which can be used for the processes of this invention include both easily processed materials and materials which would be difficult or impossible to process using traditional or other non-conventional methods. Easily processed materials which can be used in the practice of this invention include ferrous and nonferrous metals such as steel aluminum, copper, silver, and gold and mixtures thereof. For example, stainless steel is a useful material for processing into wires or rods which have high strength, ductility, corrosion resistance and wear resistance.

Examples of materials that are generally difficult to process using previously known methods include refractory metals such as tungsten, molybdenum, niobium,

vanadium, rhenium, and tantalum; reactive metals such as titanium, zirconium and hafnium; and toxic or hazardous materials such as beryllium, cobalt and nickel.

The inventive method and apparatus can be used to process precious metals such as gold, silver, iridium, paladium, or platinum.

Blended or mixed powders may be fused into alloys or composite mixtures to form materials not commercially available in any form, or to make otherwise available materials more economically or with improved properties. Figure 5 shows a metallographic cross section of a nickel based alloy rod made using a layered deposition path. Figures 6a and 6b show, respectively, a metallographic cross section and a longitudinal section of a titanium aluminum alloy rod.

Two examples of useful intermetallic compounds which can be made using the present invention are nickel aluminide (NiAl) and molybdenum disilicide (MoSi2), neither of which is yet available commercially in wire or rod form.

A number of alloys and composite mixtures of materials which display specific characteristics which may complicate or make difficult processing in previously known methods can be processed easily using the present invention.

Examples of materials which can be processed into wire or rod using the present invention include alloys and mixtures having abrasion, corrosion, wear or high temperature resistance, high impact strength, brittleness or hardness, such as cobalt based alloys and composite materials that contain hard fibers or particles such as tungsten carbide.

Materials for the production of wire or rod in accordance with the present invention can be chosen for the desired economics, facility of processing and desired

properties. For example, Figure 7 shows wire segments of 316 stainless steel, pure tungsten, nickel aluminide and molybdenum disilicide made in accordance with the invention process. Although nickel aluminide and molybdenum disilicide are generally brittle, and pure tungsten rods can be bent only once or twice, rods made of stainless steel can be repeatedly bent, thus displaying ductility and the ability to spool these materials.

In most embodiments of the invention, particulate material which is not fused may be used again. Deposited material may be passed through a seal or vent allowing sectioning and packaging outside the controlled purity growth environment.

Contaminants such as drawing lubricants or carbon pickup from drawing or swaging dies can cause defects in subsequent use of the contaminated wires or rods.

Materials with properties which are made less desirable by picking up of contaminants during conventional processing methods can be used in the practice of the present invention. An example of such materials are the cobalt based filler materials used for the re-conditioning of turbined blades. Pickup of lubricants and carbon during conventional processing render these alloys useless for this type of repair and require very slow and/or expensive alternative processing methods such as quartz casting.

Conventional casting methods are limited to casting rods of many millimeters in diameter. When small diameter rods are required, these cast rods are then ground to as small as 0.5 mm or less. The expensive grinding process creates large amounts of waste and is a very costly way of producing wire or rods. The invention method produces materials as good or better than those produced by the conventional methods in a single step without waste.

With use of this invention it is possible to manufacture wires and rods having greater purity than the purity of the powder used for deposition because the heat and melting occurring in the deposition zone can form gases of impurities which are then driven off. For example, grade B powder can be refined during forming to produce grade A wire.

The benefits of powder metallurgy techniques in the production of commercial shapes are improved upon by the reduction in tooling and processing steps and quality of resultant material deposit of the present invention. This invention makes many powder metallurgy techniques obsolete by an even further reduction in processing steps.

Flow charts comparing the steps of the invention method with the steps of conventional wire or rod manufacture are shown in Figures 8a and 8b. It can be seen that the invention significantly reduces the manufacturing steps.

Particulate material suitable for use in this invention can be made by re- melting cast ingots and atomizing the molten metal by injecting gas, water, mechanically spinning the liquid, or pouring the liquid onto a high speed spinning plate. The chemically segregated ingot is randomized by this process of making particulate material by atomization of re-melted cast ingots because the small powder particles are distributed randomly, collected and reconsolidated during formation of the elongated articles in accordance with the process of this invention.

Particulate material generally most suitable for use in this invention is usually in larger particle sizes than those considered to be hazardous or carcinogenic due to suspension of the particles in air. These larger particle sizes as well as a spherical

shape are desirable due to the flow characteristics, though the use of smaller and/or irregular shaped particles has been demonstrated using the present invention. In many cases, such as processing of refractory metals, powder is the fundamental form of the metal as a result of the extraction methods used to produce the metal. In other cases, powder is already readily available commercially for powder metallurgy or thermal spraying processes. Particle sizes which can be used in the practice of this invention are generally in the range from about 1 micron to about 250 microns. Presently preferred are particle sizes in the range from about 5 microns to about 150 microns.

Presently most preferred are particle sizes in the range from about 50 microns to about 100 microns, depending upon such parameters as powder morphology (spherical, angular, irregular), material density, packing density and powder flow characteristics.

The raw material which does not become part of the wire or rod is easily collected and reused without any additional processing or reprocessing. The economic benefit of recycling unfused, uncontaminated material makes the invention method attractive for processing of rare or expensive materials and makes the process essentially waste free.

Inert gas purity suitable for use in the present invention is generally in the range from less than 1 ppm to greater than 200 ppm oxygen and water, depending upon purity and properties of product desired for the intended end use. Presently preferred for making wire or rod from high strength, hard or refractory alloys such as nickel-, cobalt- and tungsten-based alloys in gas purity in the range from about 5 ppm to about 50 ppm oxygen and water. Materials less reactive to oxygen or nitrogen can be formed in atmospheres containing higher concentrations of oxygen and water. The

degree to which oxygen and water must be excluded depends upon the grade or quality of product desired. For example, for making an A or B grade product, gas purity ranging from about 50 to about 150 ppm generally can be used.

The ability to directly form metal parts by the directed light fabrication process of this invention offers the advantage of structural integrity gained by achieving full mechanical strength in the metal deposit. The process and apparatus of this invention enables the manufacture of highly homogenous, pure forms of commercially useable shapes in a manner which has improved cost effectiveness, speed, quality and ranges of materials which may be processed.

Fully dense metal wires and rods having uniform surface texture, composition and diameter can be made by deposition along a single vertical axis parallel to the axis of the laser beam.

Wire or rod made by the laser deposition process of this invention is relatively free of internal stresses in comparison to wire or rod made by traditional methods because the continuous solid/liquid interface region produced in the invention process yields fully dense components. This contrasts to other near net shape liquid powder techniques (e.g., thermal spraying) in that a molten droplet does not impact onto a solid substrate, and as a result, structural integrity degradations attributed to splat gaps and other pore defects are absent.

Wire or rod made from the directed light fabrication process of this invention has annealed properties, that is, its microstructure and metallurgical properties are similar to those of articles which have been annealed. Figures 9a, 9b, and 9c, show the powder used, microstructure as shown in a micrograph of a polished cross section

and fracture surface of a wire made in accordance with the invention from 316 stainless steel. Figures 10a, Ob, and l Oc, show the powder used, microstructure as shown in a micro graph of a polished cross section and fracture surface of a wire made in accordance with the invention from tungsten. Figures 1 lea,1 lb, and 1 lc, show the powder used, microstructure as shown in a micrograph of a polished cross section and fracture surface of a wire made in accordance with the invention from nickel aluminide, and figures 12a, 12b, and 12c, show the powder used, microstructure as shown in a micrograph of a polished cross section and fracture surface of a wire made in accordance with the invention from molybdenum disilicide.

If the material of the wire or rod made from the directed light fabrication process is heat-treatable, the properties of the wire or rod, such as strength, ductility, fracture toughness, and corrosion resistance, can be modified by means of heat treatment.

Surface melting of partially fused powder particles can be achieved by directing a portion of the laser beam to remelt the surface after the initial deposition process to create a smoother surface if desired.

There is no need to dispose of excess lubricants used in drawing wire or rod and no need to clean lubricants from drawn wire or rod made by the directed light fabrication processes of this invention because use of lubricants is unnecessary. The waste stream resulting from the invention process is virtually eliminated. No contamination is left on the surface of the wire or rod, so subsequent steps generally used to remove contamination such as solvent cleaning or grinding are not required.

However, grinding, rolling, swaging or other forming operations may be employed as secondary operations to impart further characteristics to the deposited materials.

The following examples will demonstrate the operability of the invention.

EXAMPLE I Fifty 3/4" diameter rods were made with equipment set up as shown in Figure 1.

One gallon of particulate InconelTM 690 powder (a nickel based alloy containing about 60% nickel, and minor amounts of iron and cobalt) commercially available from Inco Alloys, Inc. was placed into an Accurate 1/3 ft3 capacity powder feeder. The InconelTM powder ranged in spherical particle size from 44 microns to 149 microns.

The powder was fed by a screw-type feed to an eductor where argon delivery gas was used to take the powder to a splitter which divided the powder into 8 streams in tubes connected to a nozzle at the laser head.

At the laser head the 8 multiple streams of powder were delivered so as to achieve a precise focus of the powder streams at a position cofocal to the laser beam.

A 5-axis Laserdyne 94 directed light fabrication system controller (commercially available from Laserdyne in Eden Prarie, MN) was used to articulate the laser head with respect to the deposited material so that continuous fusion and build up of material was achieved.

The controller used a Intel 486 PC type computer to control the 5-axis drive control boards and the control laser by means of an RS-232 serial port. It had a

graphical user interface to allow setup and execution of the machine and motion control program.

A LumonicsTM two-kilowatt continuous wave Nd:YAG laser, commercially available from Lumonics in Livonia, MI was used to generate the 1.06 micron wave length laser energy to melt the powder and provide a focused laser spot, accurate enough to form small wires.

Deposition of the parts was achieved by using 300 watt laser power, 45 inch per minute travel speed, a powder feed of 7 to 15 grams per minute, and 3.44 standard liters per minute of argon gas. Atmosphere purity in the environment chamber was maintained at 50 ppm oxygen and water. Overlap of one circular pass upon the next adjacent pass was 0.12". The increment of vertical movement used to build up the shaped cylinder was 0.15" per layer.

The apparatus was set up as shown in Figure 1 in the manner described in the specification hereof.

Commercially available CAD-CAM software (ProENGINEER from Parametric Technology, Waltham, Massachusetts) was used to produce a three- dimensional solid model of a rod from which deposition path location files were generated. The deposition path location files were input into a custom made post processor program using a NC POST PLUSTM software tool commercially available from CAD/CAM Resources, Inc., Rio Rancho, NM. A circular deposition path type such as that shown in Figure 4c was used.

The post processor was used for translating the deposition path location file into motion commands specific to the 5-axis directed light fabrication system controller.

An example of the computerized numerical control (CNC) output file used is shown in Table 1. This computer program was used to fabricate a 0.75" outside diameter, 0.50" long rod. The computer program was produced using CAD CAM software.

TABLE 1 CNC Output File for Deposition Path Commands Comments &num G1 ; linear interpolation F45 ; feed rate inches per minute G92XYZ ; reset XYZ to O &num lOG90 ; absolute positioning #15G70 ; inch programming #20G07 ; constant velocity TABLE 1 (continued) Commands Comments V1=0 ; counter variable V2=.015 ; z increment V3=0.750/V2/4 ; path variable Q5RV3 ; run subroutine 5 V3 times

MO ; program stop M5S5 ; start of subroutine 5 V1=V1+V2 ; increment variable VI &num 280X.366ZV1 ; move G4X1 ; dwell M100 ; shutter open, beam on, powder on #285G3I-.366JO. ; motion commands follow #45G3I.-366JO.

&num SOX.351 #55G3I.-351JO.

#60X.336 #65G3I-.36JO.

#70X.321 #75G3I-.321JO.

#80X.306 &num 85G2I-.306JO.

#90X.291 #95G3I-.291JO. ft 1 00X.276 TABLE 1 (continued) Commands Comments #105G3I.-276JO.

#110X.261 #115G3I.-261JO.

#120X.246 #125G3I-.246JO.

#130X.231

#135G3I.-231J0.

#140X.216 #145G3I.-216J0.

#150X.201 #155G3I-.201JO.

#160X.186 #165G3I-.186JO.

#170X.171 #175G3I-.171JO.

#180X.156 #185G3I-.156JO.

#190X.141 #195G3I-.141J0.

#200X.126 #205G3I.-126J0.

#210X.111 #215G3I.-111J0.

TABLE 1 (continued) Commands Comments #220X.096 #225G3I.-096J0.

#230X.081 #235G3I-.081J0.

#240X.066 #245G3I-.066J0.

#250X.051 #255G3I.-051J0.

#260X.041

#265G3I-.041JO.

V1=V1+V2 X.031 G3I.-031J0.

X.016 G31-.016J0.

X-.016 ZV1 V1=V1+V2 #280X-.366 G4X1 M100 #285G3I.366J0.

#50X-.351 #55G3I.351J0.

TABLE 1 (continued) Commands Comments #60X-.336 #65G3I.366J0.

#70X-.321 #75G3I.321JO.

#80X-.306 #85G3I.306J0.

It90X-.29l #95G3I.291J0.

11100X-.276 #105G3I.276J0.

#110X-.261

#115G31.261J0.

#120X-.246 #125G3I.246J0.

#130X-.321 #135G3I.231JO.

#140X-.216 #145G3I.216J0.

#150X-.201 #155G3I.201J0.

#160X-.186 #165G3I.186J0.

#170X-.171 #175G3I.171JO.

TABLE 1 (continued) Commands Comments #180X-.156 #185G3I.156J0.

#190X-.141 #195G3I.141JO.

#200X-.126 #205G3I.126J0.

#210X-.111 #215G3I.111J0.

#220X-.096 #225G3I.096J0.

#230X-.081 #235G3I.08J0.

#240X-.066 #245G3I.066J0.

#250X-.051 #255G3I.051J0.

#260X-.041 #265G3I.041J0.

V1=V1+V2 X-.031

TABLE 1 (continued) Commands Comments <BR> <BR> <BR> <BR> G3I.031JO. <BR> <BR> <BR> <P> X-.016 <BR> <BR> <BR> G3I.16JO.

M101 ; shutter closed, beam off, powder off M6 ; end of subroutine The post processor was also used to add machine commands to control the laser beam power, laser shutter, powder flow and part speed and written to the CNC output file. A 1/4" thick, 6" diameter steel plate was used as a starting support. The steel plate starting support was placed into the inert environment chamber and aligned with the motion system axis.

The CNC file was loaded into the directed light fabrication system controller memory and executed to form uniform, fully dense rods having a 3/4" diameter.

Each of the rods produced was separated from the starting support by saw cutting.

The rod samples produced were cut from the steel plate using a metal saw and sliced into 3/4" tall half sections . The sections of nickel alloy rod were mounted in 1 " diameter standard metallographic mounts using epoxy. The cut surfaces of the rods were then polished and etched, to reveal the microstructures of the rods. The

microstructures of the rods were examined at magnifications ranging from 1 OX to 600X. The examination showed that the rods produced were fully dense as shown in the cross section of Figure 5. The deposited layers showed up in the structure and were delineated by changes in the surface of the structure at the layer boundaries. The microstructure shows the previous layer corresponding with the step up height in the vertical Z direction of the laser beam relative to the deposit. Continuous epitaxial growth was found across many layers.

The microstructural development in the samples processed in accordance with this invention typically displayed continuous morphologies as well as refined segregation features, indicating a constant solid/liquid interface and rapid solidification kinetics.

EXAMPLE II A set of runs was made using the invention process to make fifty titanium/aluminum alloy rods in a range of diameters from 0.050" to 0.150".

Equipment was set up as diagrammed in Figure 1 and described in Example I.

A LumonicsTM two-kilowatt continuous wave 1.06 micron Nd:YAG laser was set to generate a 235 watt laser beam which was focused co-axially with a stream of - 180 to +325 mesh particle size spherical powder commercially available from Crucible Research in Oakdale, PA.

A spiral deposition path having a 0.050" diameter circular motion/revolution was programmed directly into the Laserdyne 94 controller. Other systems parameters

were: 50 inches per minute motion, 5 to 50 ppm oxygen and water content of the atmosphere in the box, 3.4 slpm argon delivery gas, 15 g/min powder flow.

The powder was 48% titanium, 48% aluminum, 2% niobium and 2% cromium.

Some of the rods were grown vertically using a single axis of motion (without use of the spiral tool path) at 122 watts at a linear speed of 4 to 16 inches per minute.

Machine commands were edited directly into the console of the motion controller and laser controller interface to start the flow of powder and laser energy and to begin the motion.

A helical deposition path was programmed directly into a Laserdyne 94 motion controller to form a titanium/aluminum alloy rod of 0.100" diameter.

Using the helical deposition path program, a uniform density, 0.125" diameter titanium/aluminum rod was also formed. Although this very hard material would be extremely difficult to process by existing conventional methods, the titanium/aluminum rod was relatively easy to form using the invention process.

The 13" long rods were observed to have a uniform cross sectional area and a surface of partially fused powder. Some rods were centerless ground to demonstrate that the rods could be reduced in size to rods having cross sectional diameters as small as 0.028".

Metallographic sectioning and microscopic inspection as described in Example I was used to determine full density. No discoloration of the surface was observed; lack of coloration indicated a pure, uncontaminated, as deposited surface.

Epitaxial grain growth was observed along the length of the rod by microscopic inspection at a magnification of 400X.

The samples produced in this example were also tested using a scanning electron microscope electron dispersive spectroscopy system to determine the chemistry of the samples. This test showed that the samples had the same proportionate amounts of materials as were introduced into the process in powder form. Therefore, there had been no preferential vaporization of the starting materials during processing. This demonstrated that the chemical composition of the starting material was not affected by this method of processing.

Figures 6a and 6b show, respectively, a cross section and longitudinal section of the rod formed in this example.

EXAMPLE III Equipment was set up as depicted in Figure 1, in the manner described in Example I.

A single axis of motion was used to fuse pure tungsten into wire. A pulsed Nd:YAG laser (LumonicsTM 701) was used along with an AnoradTM II motion controller to achieve semi-automatic process control. Commands were entered manually into the laser and motion system as well as manual operation of the gas and powder flow control.

The atmosphere purity used for this example was 5 ppm oxygen and water.

The support structure used to begin wire deposition was a metal plate from which wires were cut off after growth.

Rods were grown using 100 watts of power at a speed of 5 inches per minute and a powder feed rate of 5 grams/minute. Spherical tungsten powder was used in a size range from 5 microns to 50 microns.

The samples produced in this example were subjected to simple bending of greater than 90" to demonstrate the ductility of the soft annealed microstructure of the tungsten deposit. After 1 to 2 bends, the rods broke. The fracture surfaces were examined with a scanning electron microscope at 1 500X magnification. No voids or discontinuities were observed.

The ductility demonstrated by the number of bends possible before breaking of the invention sample rods was clearly superior to similar pure tungsten welding rods of the same dimensions made by conventional methods, because the conventional tungsten welding rods could not be bent at all without breaking.

The tungsten rod samples produced in this example were metallographically tested for full density in the manner described in Example I. The tungsten deposited in accordance with the invention as described in this example was determined to be fully dense by metallographic cross sectioning.

While the apparatuses, articles of manufacture, methods and compositions of this invention have been described in detail for the purpose of illustration, the inventive apparatuses, articles of manufacture, methods and compositions are not to be construed as limited thereby. This patent is intended to cover all changes and modifications within the spirit and scope thereof.

INDUSTRIAL APPLICABILITY The invention is useful for making a large variety of wire, rod or other elongated shapes from a variety of materials including materials not commercially available or specialty materials such as refractory metals. Articles made in accordance with the invention can be used for such diverse applications as filler wires for repair of aircraft, aerospace and marine components, precision hard facing, refractory components for space applications, heating elements, filaments, emitters, high temperature furnace hardware, and wherever wires or rods with specialty components or unusual cross sections are needed.