ELECTROFORMED NICKEL-CHROMIUM ALLOY

Abstract

An article comprising a turbine component formed of a nickel-chromium (NiCr) alloy including from 2 to 50 wt % chromium balanced by nickel is disclosed. The NiCr alloy is thicker than at least 125 m to make a self-supporting turbine component, and the turbine component includes a rotor blade, a stator, or a vane. The NiCr alloy is electroformed on a mandrel by providing an external supply of current to an anode and a cathode in a plating bath containing a solvent, a surfactant, and an ionic liquid including choline chloride, nickel chloride, and chromium chloride.

Claims

1. An article comprising a turbine component electroformed of a nickel-chromium (NiCr) alloy including from 2 to 50 wt % chromium balanced by nickel, wherein the NiCr alloy is thicker than 10 m.

2. The article of claim 1, wherein the NiCr alloy comprises from 8 to 20 wt % chromium balanced by nickel.

3. The article of claim 1, wherein the NiCr alloy is thicker than 125 m.

4. The article of claim 1, wherein the turbine component is a rotor blade or a stator.

5. The article of claim 1, wherein the turbine component is a vane.

6. A method for electroforming a nickel-chromium (NiCr) alloy, comprising: providing a plating bath containing a solvent, a surfactant, and an ionic liquid including choline chloride, nickel chloride, and chromium chloride, wherein a molar ratio of the choline chloride, combined chromium chloride, and nickel chloride ranges from 0.5 to 3.5 and the solvent comprises from 5 to 80 vol. % relative to a volume of a pre-mixed choline chloride and metal chlorides including both nickel chloride and chromium chlorides; and electroforming the NiCr alloy onto the mandrel by providing an external supply of current to an anode and a cathode, wherein the mandrel is removed after the NiCr alloy is electroformed.

7. The method according to claim 6, wherein the anode is an insoluble anode.

8. The method according to claim 6, wherein the anode is a NiCr alloy anode, a Ni anode, or a Cr anode.

9. The method according to claim 6 further comprising pre-treating the mandrel prior to electroforming the NiCr alloy.

10. The method according to claim 6, wherein a protective coating is applied on the electroformed NiCr alloy.

11. The method according to claim 6, wherein the current is a direct current or an alternating current.

12. The method according to claim 6, wherein the solvent is a polar protic solvent.

13. The method according to claim 6, wherein the solvent is a polar aprotic solvent.

14. The method according to claim 6, wherein the solvent is chosen from one or more of formic acid, citric acid, isopropanol (IPA), water, acetic acid, and ethylene glycol.

15. The method according to claim 6, wherein the surfactant is an anionic, a cationic, or an amphoteric surfactant.

16. The method according to claim 6, wherein the surfactant is either sodium dodecyl sulfate, fluorosurfactants, cetyl trimethylammonium bromide (CTAB), or cetyl trimethylammonium chloride (CTAC).

17. The method according to claim 6, wherein the electroformed NiCr alloy comprises from 2 to 50 wt % chromium balanced by nickel.

18. The method according to claim 6, wherein the electroformed NiCr alloy comprises from 8 to 20 wt % chromium balanced by nickel.

19. The method according to claim 6, wherein the electroformed NiCr alloy is thicker than 125 m.

20. A method for electroforming a nickel-chromium (NiCr) alloy, comprising: providing a plating bath containing a solvent, a surfactant, and an ionic liquid including choline chloride, nickel chloride, and chromium chloride, wherein a molar ratio of the choline chloride, combined chromium chloride, and nickel chloride ranges from 0.5 to 3.5 and the solvent comprises from 5 to 80 vol. % relative to a volume of a pre-mixed choline chloride and metal chlorides including both nickel chloride and chromium chlorides; and electroforming the NiCr alloy onto the mandrel by providing an external supply of current to an anode and a cathode, wherein the mandrel is removed after the NiCr alloy is electroformed, wherein the electroformed NiCr alloy comprises from 2 to 50 wt % chromium balanced by nickel, and wherein the electroformed NiCr alloy is thicker than 125 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 illustrates a plating bath filled with an electrolytic solution for electroforming a NiCr alloy according to an embodiment of the present disclosure.

[0014] FIG. 2 illustrates an article comprising an electroformed NiCr alloy according an embodiment of the present disclosure.

[0015] FIG. 3 is a flow chart of an electroforming NiCr alloy process of the present disclosure.

[0016] The drawing(s) depict various preferred embodiments of the present invention for purposes of illustration only. One skilled in the art will readily recognize from the following discussion that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the invention described herein.

DETAILED DESCRIPTION

[0017] Electroforming is a metal forming process that forms self-supporting metal parts or components through electrodeposition. Electroforming a NiCr alloy is a cost-effective and environmentally friendly method to make some high temperature-resistant turbine engine components with complex geometries and tighter tolerance.

[0018] According to an aspect of the present disclosure, an electroformed nickel-chromium (NiCr) alloy for use as a turbine component is disclosed. The NiCr alloy comprises from 2 to 50 wt % chromium and the balance nickel, and can be made thicker than at least 10 m to form self-supporting turbine components. The Figure illustrates a plating bath containing an electrolyte solution for electroforming a NiCr alloy according to an aspect of the present invention.

[0019] FIG. 1 illustrates a plating bath filled with an electrolytic solution for electroforming a NiCr alloy according to an embodiment of the present disclosure Referring now to FIG. 1, there is provided a plating bath 102 containing an electrolytic solution that consists of a room temperature ionic liquid, namely deep eutectic solvent, including choline chloride, nickel chloride, chromium chloride, solvents, and surfactants like anionic, cationic, or Zwitterionic (amphoteric) surfactants. The surfactant can be one of sodium dodecyl sulfate, fluorosurfactants, cetyl trimethylammonium bromide (CTAB), or cetyl trimethylammonium chloride (CTAC). It is noted that the choline chloride based metal processing is low-cost and environmentally friendly. In one embodiment, a molar ratio of the choline chloride and chromium chloride ranges from 0.5 to 3.5. A turbine component is produced by depositing a metal onto a base form, known as a mandrel 104 which is removed after electroforming is done.

[0020] In the embodiment, polar aprotic and polar protic solvents are used to adjust the viscosity and conductivity of the plating bath 102 to attain high quality NiCr alloy deposits. Specifically, protic solvents are preferred due to their ability to donate hydrogen bonds. The solvents include formic acid, citric acid, Isopropanol (IPA), water, acetic acid, and ethylene glycol.

[0021] According to one embodiment, preferred solvent content is from 10 to 80 vol % relative to the mixture of choline chloride and metal chlorides including the nickel and chromium chlorides on a pre-mixing basis. Referring to FIG. 1, electroforming the NiCr alloy begins by providing an external supply of current to an anode and a cathode. The mandrel is the cathode. The current can be a direct current (DC) or an alternating current (AC) including a pulse or pulse reverse current (not shown). The regime and/or magnitude of the current can be controlled during the deposition to achieve desired coating composition, density, and morphology.

[0022] When the current is supplied, the metal at the soluble anode is oxidized from the zero valence state to form cations with a positive charge. Metal cations, generally in complex forms in the presence of anions in the solution, are reduced at the cathode to deposit in the metallic, zero valence state. The result is the effective reduction and transfer of Ni and Cr ionic species from the electrolytic solution to the mandrel 104. The mandrel 104 is removed after the electroforming is done.

[0023] The turbine component to be made is electroformed on the mandrel 104 which is a cathode during electrodeposition. The anode is made of the metal to be plated on the mandrel, and includes a NiCr alloy anode, a Ni and/or Cr anode, or any combination of these materials can be chosen to satisfy different requirements. An insoluble catalytic anode (catalyzing oxygen evolution, hexavalent chromium formation) is preferable, but the anode used is not specifically limited. A combination of soluble Ni anode and an insoluble catalytic anode can be used to control bath composition during the course of electrodeposition as well.

[0024] The mandrel is pre-treated prior to electrodeposition. The pre-treatment includes degreasing, cleaning the surface, and activation before being placed in the plating bath for electrodeposition. To enhance mass transport, the mandrel 104 can be moved in either a rotating or reciprocating mode or the electrolytic solution can be agitated during the electroforming process. The electroforming process inevitably decomposes water in the bath 102, and thus the solution in the bath is replenished to maintain consistent deposition quality.

[0025] FIG. 2 illustrates an article comprising an electroformed NiCr alloy according an embodiment of the present disclosure. Feasibility of thick electroformed NiCr alloys has been demonstrated by electroforming a NiCr alloy which is thicker than 125 m to make turbine components. In one embodiment, an article 200 comprises an electroformed NiCr alloy 202 that includes from 2 to 50 wt % chromium balanced by nickel, and is thicker than at least 10 m which was not attainable through the conventional methods.

[0026] In another embodiment, although not specifically limited, an electroformed NiCr alloy 202 comprises from 8 to 20 wt % chromium balanced by nickel. In the embodiment, the NiCr alloy is thicker than 125 m to make a self-supporting turbine component. Optionally, a protective coating 206 can be applied on a surface 204 of the NiCr alloy 202 to impart further oxidation resistance to the article 200. The protective coating 206 may include aluminum and a bond coat and other thermal barrier coatings. Heat treatment may be performance on the structure.

[0027] FIG. 3 is a flow chart of an electroformed NiCr process of the present disclosure. Referring now to FIG. 3, forming a thick electroformed NiCr alloy to make turbine parts begins at step 300 where a part to be made or a mandrel is pre-treated prior to electroforming a NiCr alloy to remove foreign materials on the surface of the part of mandrel. At step 302, a plating bath filled with a solution including a solvent, a surfactant, and an ionic liquid is provided. At step 304, the NiCr alloy is electroformed on the part or mandrel by providing an external supply of current to an anode and a cathode. The mandrel can be moved in a rotating or reciprocating mode during the electroforming process to increase the deposition rate. The electroforming step 304 is done when the NiCr alloy reaches the desired thickness.

[0028] After the electroforming is done at step 304, optionally, a protective coating 206 may be applied at step 306. In one embodiment, the protective coating 206 may include a bond coat or a thermal barrier coating. The protective coating 206 may be applied to a surface 204 of the electroformed NiCr alloy 202 at step 306 to impart oxidation resistance to the NiCr alloy 202. The disclosed choline chloride based electroforming is a metal forming process that is cost-effective to make high temperature-resistant turbine parts with complex geometries and tighter tolerance, and is environmentally friendly.

[0029] It is to be understood that the disclosure of the present invention is not limited to the illustrations described and shown herein, which are deemed to be merely illustrative of the best modes of carrying out the disclosure, and which are susceptible to modification of form, size, arrangement of parts, and details of operation. The disclosure is intended to encompass all such modifications which are within its spirit and scope of the invention as defined by the following claims.