COMPONENTS

TECHNICAL FIELD

[0001] The present invention relates generally to a process and apparatus for additive manufacturing of a nickel based superalloy component.

DESCRIPTION OF RELATED ART

[0002] Additive manufacturing is a process that builds up a component by layer by layer basis. During additive manufacturing process, powder material of the component is deposited onto a working surface. Many layers are formed on top of each other in a sequence to achieve a net shape or near net shape component. A heat source, such as a laser beam, is directed onto a working surface. The location is melted by the laser beam and powder is fused the location.

[0003] Superalloys are materials with excellent resistance to mechanical and chemical property degradation at high temperatures. Nickel (Ni) based superalloys are based upon base metal nickel (Ni) and typically contain numerous other elements such as chromium (Cr), aluminum (Al), titanium (Ti), tungsten (W), cobalt (Co), tantalum (Ta), carbon (C), among others. Ni based superalloys can be used for applications in which high mechanical strength and oxidation resistance at high temperatures is requires, such as turbine blades.

[0004] There is a desire to use laser additive manufacturing (LAM) for Ni based superalloy components. However, Ni based superalloys are generally considered to be difficult to weld or LAM due to their tendency to grain boundary cracking, in particular Ni based superalloys with high proportion of gamma prime. Gamma prime is largely responsible for the high temperature strength of the Ni based superalloys and resistance to creep deformation. If a high temperature heat treatment or process exceeds the grain boundary melting temperature (also called incipient melting temperature (IMT)) of the base metal, properties of the superalloy are impaired. SUMMARY OF INVENTION

[0005] Briefly described, aspects of the present invention relate to a process and apparatus for additive manufacturing of a nickel based superalloy component.

{0006} According to an aspect, a process for additive manufacturing of a Ni based superalloy component is presented. The process comprises applying a Ni based coating to a surface of the Ni based superalloy component. A melting temperature of the Ni based coating is adjusted to below an incipient melting temperature of the Ni based superalloy component. The process comprises depositing powder onto a surface of the Ni based coating by a powder delivery device. The powder comprises a substantially similar composition with the Ni based superalloy component. The process comprises emitting an energy beam directed to the Ni based coating by an energy source. The process comprises controlling an amount of energy delivered by the energy beam such that the surface of the Ni based coating interacted with the energy beam is melted to form a molten pool. A temperature of the molten pool is adjusted to above the melting temperature of the Ni based coating. The temperature of the molten pool is adjusted to below the incipient melting temperature of the Ni based superalloy component. The temperature of the molten pool is adjusted to below a melting temperature of the powder comprising the substantially similar composition with the Ni based superalloy component. An additive layer is built by depositing the powder into the melted Ni based coating without melting the Ni based superalloy component and without melting the powder comprising the substantially similar composition with the Ni based superalloy component.

[0007] According to an aspect, an apparatus for additive manufacturing a Ni based superalloy component is presented. A Ni based coating is applied to a surface of the Ni based superalloy component. The apparatus comprises a powder delivery device that is configured to deposit powder onto a surface of the Ni based coating. The powder comprises a substantially similar composition with the Ni based superalloy component. The apparatus comprises an energy source that is configured to emit energy beam directed to the Ni based coating. A melting temperature of the Ni based coating is adjusted to below an incipient melting temperature of the Ni based superalloy component. An amount of energy delivered by the energy beam is controlled by the energy source such that the surface of the Ni based coating interacted with the energy beam is melted to form a molten pool. A temperature of the molten pool is adjusted to above the melting temperature of the Ni based coating. The temperature of the molten pool is adjusted to below the incipient melting temperature of the Ni based superalloy component. The temperature of the molten pool is adjusted to below a melting temperature of the powder comprising the substantially similar composition with the Ni based superalloy component. An additive layer is built by depositing the powder into the melted Ni based coating without melting the Ni based superalloy component and without melting the powder comprising the substantially similar composition with the Ni based superalloy component.

[0008] According to an aspect, a Ni based superalloy component to be

manufactured by an additive manufacturing process is presented. The Ni based superalloy component comprises a Ni based coating applied to a surface of the Ni based superalloy component. A melting temperature of the Ni based coating is adjusted to below an incipient melting temperature of the Ni based superalloy component.

[0009] Various aspects and embodiments of the application as described above and hereinafter may not only be used in the combinations explicitly described, but also in other combinations. Modifications will occur to the skilled person upon reading and understanding of the description.

BRIEF DESCRIPTION OF DRAWINGS

[0010] Exemplary embodiments of the application are explained in further detail with respect to the accompanying drawings. In the drawings:

[0011] FIG. 1 illustrates a schematic diagram of an apparatus and a process for additive manufacturing of a Ni based superalloy component according to a

conventional process; [0012] FIGs. 2 to 3 illustrate schematic diagrams of an apparatus and a process for additive manufacturing a Ni based superalloy component according to an embodiment of the invention; and

[0013] FIGs. 4 to 6 illustrate schematic diagrams of an apparatus and a process for additive manufacturing a Ni based superalloy component according to another embodiment of the invention.

[0014] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.

DETAILED DESCRIPTION OF INVENTION

[0015] A detailed description related to aspects of the present invention is described hereafter with respect to the accompanying figures.

[0016] FIG. 1 illustrates a schematic diagram of an apparatus 100 and a process for additive manufacturing a Ni based superalloy component 200. As illustrated in FIG. 1, the apparatus 100 may include a chamber 110 and an energy source 120. The energy source 120 may include laser, arc, plasma, electron beam, etc. ANi based superalloy component 200 is placed inside the chamber 110. The energy source 120 moves along a surface 210 of the Ni based superalloy component 200 and emits the energy beam 122 directed to the Ni based superalloy component 200. The Ni based superalloy component 200 may include, for example, 713C, 247, PW1480, MARM200, R77, PW1483, R80, U720, 738 or mixtures thereof.

[0017] The apparatus 100 may include a powder delivery device 130 for depositing powder 132 onto the surface 210 of the Ni based superalloy component 200. The powder 132 may consist of substantially similar composition with the Ni based superalloy component 200. The powder delivery device 130 may move along the surface 210 of the Ni based superalloy component 200 in front of the moving of the energy source 120. The powder 132 may be delivered by a laser beam. The powder delivery device 130 may be integrated with the energy source 120.

[0018] During an additive manufacturing process, the energy source 120 controls an amount of energy delivered by the energy beam 122 such that the surface 210 of the Ni based superalloy component 200 interacted with the energy beam 122 is melted to form a molten pool 124 at the surface 210 of the Ni based superalloy component 200. Temperature of the molten pool 124 is above the melting temperature of the Ni based superalloy component 200 and above the melting temperature of the powder 132. The powder 132 is fused into the surface 210 of the Ni based superalloy component 200. An additive layer 140 is thus built up on the Ni based superalloy component 200.

[0019] During the additive manufacturing process, temperature of heat affected zone (HAZ) adjacent to the molten pool 124 necessarily goes above the IMT of the Ni based superalloy component 200 and thus effectively melts the grain boundaries of the Ni based superalloy component 200. In the additive manufacturing process as illustrated in FIG. 1, the energy beam 122 interacts with the Ni based superalloy component 200 directly, which causes a HAZ cracking 150 on the Ni based superalloy component 200 due to grain boundary melting. The IMT of the Ni based superalloy component 200, for example, 713C, 247, PW1480, MARM200, R80, 738 or mixtures thereof, may be around l220-l270°C.

[0020] FIGs. 2 and 3 illustrate schematic diagrams of an apparatus 100 and a process for additive manufacturing a Ni based superalloy component 200 according to an embodiment of the invention. As illustrated in the exemplary embodiment of FIG. 2, a Ni based coating 220 is applied to the surface 210 of the Ni based superalloy component 200. The powder delivery device 130 deposits powder 232 onto a surface 230 of the Ni based coating 220 of the Ni based superalloy component 200. The powder 232 consists of a substantially similar composition with the Ni based superalloy component 200. The Ni based coating 220 has a melting temperature that is below the IMT of the Ni based superalloy component 200 and below a melting temperature of the powder 232 consisting of the substantially similar composition with the Ni based superalloy component 200. [0021] According to the exemplary embodiment as illustrated in FIG. 2, during an additive manufacturing process, the energy source 120 moves along the surface 230 of the Ni based coating 220 of the Ni based superalloy component 200 and emits the energy beam 122 directed to the Ni based coating 220. The energy source 120 may control an amount of energy delivered by the energy beam 122 such that the surface 230 of the Ni based coating 220 interacted with the energy beam 122 is melted to form a molten pool 124 at the surface 230 of the Ni based coating 220. Temperature of the molten pool 124 is adjusted by controlling the amount of energy delivered by the energy beam 122. The temperature of the molten pool 124 is adjusted to above the melting temperature of the Ni based coating 220. The temperature of the molten pool 124 is adjusted to below the IMT of the Ni based superalloy component 200 and to below the melting temperature of the powder 232 consisting of the substantially similar composition with the Ni based superalloy component 200. An additive layer 240 is built by depositing the powder 232 into the melted Ni based coating 220 without melting the Ni based superalloy component 200 and grain boundaries of the Ni based superalloy component 200 and the powder 232 consisting of the substantially similar composition with the Ni based superalloy component 200. The temperature of the molten pool 124 may be monitored by a thermal sensor 160 during the additive manufacturing process. The thermal sensor 160 may be arranged on the energy source 120, or on the powder delivery device 130, or on an arrangement that is known in the industry. For illustration purpose, the thermal senor 160 is arranged on the energy source 120 as shown in the exemplary embodiment of FIG. 2.

[0022] The Ni based coating 220 may be applied to the surface 210 of the Ni based superalloy component 200 by Ni electroplating. An alloying element in the Ni based coating 220 may include, such as, phosphorus (P), boron (B), or silicon (Si), etc.

Percentage weight (%wt) of the alloying element in the Ni based coating 220 may be adjusted such that the melting temperature of the Ni based coating 220 is below the IMT of the Ni based superalloy component 200. For example, the percentage weight of phosphorus (P) in the Ni based coating 220 may be adjusted in a range of 4-12 %wt. The percentage weight of boron (B) in the Ni based coating 220 may be adjusted in a range of 3-5 %wt. The percentage weight of silicon (Si) in the Ni based coating 220 may be adjusted in a range of 4-8 %wt. The melting temperature of the Ni based coating 220 may be adjusted, for example, at least 20°C below the IMT of a Ni based superalloy component 200. The IMT of the Ni based superalloy component 200 having a composition of, such as 713C, 247, MARM200, R77, R80, 738 or mixtures thereof, may be around l270°C. The melting temperature of the Ni based coating 220 may be adjusted in a range of 850-l250°C. The inventive additive manufacturing process avoids a grain boundary melting and cracking for additive manufacturing of the Ni based superalloy component 200.

[0023] FIG. 3 illustrates a diffusion heat treatment after depositing the additive layer 240 over the surface 230 of the Ni based coating 220. The diffusion heat treatment diffuses the Ni based coating 220, for example, the alloying element in the Ni based coating 220, into the additive layer 240 and the Ni based superalloy component 200 so that the additive layer 240 may consist of substantially similar composition with the Ni based superalloy component 200. The diffusion heat treatment may be applied in a furnace 170. The furnace 170 may be a vacuum furnace. Temperature of the diffusion heat treatment applied to the Ni based coating 220 may be in a range of 1150- l250°C. Duration of the diffusion heat treatment applied to the Ni based coating 220 may be about 2-24 hours. The inventive additive manufacturing process manufactures an additive layer 240 on the Ni based superalloy component 200 without heat affected zone cracking.

[0024] Thickness of the Ni based coating 220 may be in a range of 0.075-0.125 mm. Thickness of the additive layer 240 may be in a range that is fusible into the melted Ni based coating 220. The inventive additive manufacturing process may build a thicker additive layer 240 in comparison of an additive layer 140 built by a conventional additive manufacturing process. For example, an additive layer 240 built by the inventive additive manufacturing process may have a thickness in a range of 0.1- 0.5 mm. In comparison, an additive layer 140 built by a conventional additive manufacturing process may have a thickness in a range of 0.02-0.1 mm. The inventive additive manufacturing process may provide a high efficiency of additive

manufacturing of the Ni based superalloy component 200. [0025] A thickness of an additive layer 240 may be increased through a layer by layer process by depositing a successive layer on a top of a previous layer. FIGs. 4 to 6 illustrate schematic diagrams of an apparatus 100 and a process for additive

manufacturing a Ni based superalloy component 200 through a layer by layer process according to an embodiment of the invention. As illustrated in the exemplary embodiment of FIG. 4, a Ni based coating 220 is applied to the surface 210 of the Ni based superalloy component 200. The powder delivery device 130 deposits powder 232 onto a surface 230 of the Ni based coating 220 of the Ni based superalloy component 200. In this illustrated exemplary embodiment, the powder 232 consists of a mixture of a powder having a substantially similar composition with the Ni based superalloy component 200 and a braze alloy powder having a low melting temperature. Alloying element in the braze alloy powder may consist of, such as Titanium (Ti), Zirconium (Zr), Hafnium (Hf), or combinations thereof. The powder mixture 232 may consist of up to 50% weight of the braze alloy powder. Melting temperature of the Ni based coating 220 is adjusted to below an IMT of the Ni based superalloy component 200. Melting temperature of the braze alloy powder in the powder mixture 232 is adjusted to below the IMT of the Ni based superalloy component 200 and to below a melting temperature of the powder comprising the substantially similar composition with the Ni based superalloy component 200.

[0026] During an additive manufacturing process, the energy source 120 moves along the surface 230 of the Ni based coating 220 and emits the energy beam 122 directed to the Ni based coating 220. The energy source 120 may control an amount of energy delivered by the energy beam 122 such that the surface 230 of the Ni based coating 220 interacted with the energy beam 122 is melted to form a molten pool 124 at the surface 230 of the Ni based coating 220. Temperature of the molten pool 124 is adjusted by controlling the amount of energy delivered by the energy beam 122. The temperature of the molten pool 124 is adjusted to above the melting temperature of the Ni based coating 220 and to above the melting temperature of the braze alloy powder in the powder mixture 232. The temperature of the molten pool 124 is adjusted to below the IMT of the Ni based superalloy component 200 and to below the melting temperature of the powder having the substantially similar composition with the Ni based superalloy component 200 in the powder mixture 232. A first additive layer 241 is built by depositing the powder mixture 232 into the melted Ni based coating 220 on the surface 210 of the Ni based superalloy component 200 without melting the Ni based superalloy component 200 and grain boundaries of the Ni based superalloy component 200 and the powder having the substantially similar composition with the Ni based superalloy component 200 in the powder mixture 232. The braze alloy powder in the powder mixture 232 is melted in the first additive layer 241 which may form a molten pool 124 for a successive additive layer.

[0027] To increase a thickness of an additive layer 240, a second additive layer 242 is built on the top of the first additive layer 241, a third additive layer is built on a top of the second layer 242, as illustrated in FIG. 5. The second additive layer 242 is built by depositing the powder mixture 232 into the melted braze alloy powder in the first additive layer 241. The powder in the powder mixture 232 having the substantially similar composition with the Ni based superalloy component 200 is not melted. A similar process is applied to deposit the third additive layer 243 on the top of the second additive layer 242. The melted braze alloy powder in the second additive layer 242 forms the molten pool 124 for the third additive layer 243. The process continues until a required thickness of the additive layer 240 is achieved. For illustration purpose, FIG. 5 only shows three additive layers 241, 242 and 243. It is understood that more successive layers may be built on the top of previous layers. The temperature of the molten pool 124 is monitored by a thermal sensor 160 during the additive

manufacturing process.

[0028] FIG. 6 illustrates a diffusion heat treatment to the additive layer 240 after the required thickness of the additive layer 240 is achieved. The diffusion heat treatment diffuses the Ni based coating 220 and the braze alloy powder, such as the alloying element in the Ni based coating 220 and the alloying element in the braze alloy powder, into the additive layer 240 and the Ni based superalloy component 200 so that the additive layer 240 may consist of substantially similar composition with the Ni based superalloy component 200. The diffusion heat treatment as illustrated in FIG. 6 may be similar as illustrated in FIG. 3. The inventive additive manufacturing process manufactures an additive layer 240 on the Ni based superalloy component 200 without heat affected zone cracking.

[0029] Ni based superalloys have excellent mechanical and chemical properties at high temperatures. However, due to grain boundary melting in the HA Z applied by an energy beam 122 in an additive manufacturing process, it is extremely difficult to use additive manufacturing process for Ni based superalloy component 200, especially high gamma prime Ni based superalloy component 200. According to an aspect of the proposed embodiments, the inventive additive manufacturing process provides a grain boundary melting free and cracking free additive manufacturing of a Ni based superalloy component 200.

[0030] According to an aspect of the proposed embodiments, the inventive additive manufacturing process may be used in repairing of a Ni based superalloy component 200, such as turbine blades. The inventive additive manufacturing process may efficiently build up 0.5 -2.0 mm Ni based superalloy additive layer 240 on turbine blades when repairing the turbine blades having erosion.

[0031] Although various embodiments that incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.

The invention is not limited in its application to the exemplary embodiment details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of“including,”“comprising,” or“having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms“mounted,”“connected,”“supported,” and“coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further,“connected” and“coupled” are not restricted to physical or mechanical connections or couplings.

Reference List:

100: Apparatus and Process for Additive Manufacturing

110: Chamber

120: Energy Source

122: Energy Beam

124: Molten Pool

130: Powder Delivery Device

132: Powder

140: Additive Layer

150: Heat Affected Zone Cracking

160: Thermal Sensor

170: Furnace

200: Ni based Superalloy Component

210: Surface of the Ni based Superalloy Component

220: Ni based Coating

230: Surface of the Ni based Coating

232: Powder

240: Additive Layer

241 : First Additive Layer

242: Second Additive Layer

243 : Third Additive Layer