Electrochemical machining employing electrical voltage pulses to drive reduction and oxidation reactions

Patent metadata

Field	Value
Publication number	US-10487416-B2
Application number	US-201514739109-A
Country	US
Kind code	B2
Filing date	Jun 15, 2015
Priority date	Jun 15, 2015
Publication date	Nov 26, 2019
Grant date	Nov 26, 2019

Abstract

Electrochemical machining of parts employs electric or voltage pulses in which current flows in a first direction and a second direction opposite from the first direction. The cathodic/anodic pulses switch between bulk machining and oxide removal pushing bulk material removal into a homogenous regime to obtain a smooth surface finish and appropriate form control during the electrochemical machining process compared to electrochemical machining employing an electric or voltage potential in which current flows in only one direction.

First claim

The invention claimed is:

1. A method for electrochemical machining a metallic workpiece comprising a metallic substrate to form a turbine blade, the method comprising:
applying a plurality of electric potential pulses over a period of time to cause current flow between an electrode and a metallic substrate having an electrolyte between the electrode and the metallic substrate, a first plurality of the plurality of electric potential pulses having a first electric potential (V 1 ) and a first duration (t 1 ) to cause current flow in a first direction between the electrode and the metallic substrate to drive a reduction process, and a second plurality of the plurality of electric potential pulses having a second electric potential (V 2 ) and a second duration (t 2 ) to cause current flow in a second direction opposite to the first direction between the electrode and the metallic substrate to drive oxide removal, the first electric potential (V 1 ) being greater than the second electric potential (V 2 ), the first duration (t 1 ) being greater than the second duration (t 2 ), and the first plurality of the plurality of electric potential pulses being interspersed with the second plurality of the plurality of electric potential pulses, the first plurality of the plurality of electrical pulses further comprising a third electric potential (V 3 ) and a third duration (t 3 ) to also cause current flow in a first direction between the electrode and the metallic substrate, wherein the first electric potential (V 1 ) is greater than the third electric potential (V 3 ) and the first duration (t 1 ) is greater than the third duration (t 3 );
moving the electrode and/or the metallic substrate toward each other, at a feed rate between about 0.01 inches per minute and about 0.25 inches per minute, while applying the first plurality and the second plurality of the plurality of electric potential pulses over the period of time to electrochemically machine a portion of the metallic substrate; and
wherein the metallic substrate comprises a nickel-based superalloy comprising nickel, cobalt, and chromium, and the electrochemically machined metallic substrate after the period of time comprises a surface having an average arithmetic surface roughness less than a surface roughness of an electrochemically machined metallic substrate formed with an applied electric potential resulting in current flow in only one direction, wherein moving the electrode and/or the metallic substrate toward each other while applying the plurality of electric potential pulses over the period of time removes a portion of the metallic substrate having a thickness greater than 0.02 inch to form at least a portion of the turbine blade; and wherein the electrochemically machined metallic substrate after the period of time comprises a surface having an average arithmetic surface roughness less than about 20 microinch.

2. The method of claim 1 wherein the metallic substrate comprises a first configuration, the electrode comprises a second configuration the reverse of which is different from the first configuration, and wherein the moving comprises moving the electrode and/or the metallic substrate toward each other while applying the first plurality and the second plurality of the plurality of electric potential pulses over the period of time to electrochemically machine a portion of the metallic substrate so that the first configuration of the metallic substrate has a reverse configuration of the electrode.

3. The method of claim 1 wherein the first duration (t 1 ) of the first electric potential pulses comprise about 0.1 second to about 1 second, and the second duration (t 2 ) of the second electric potential pulses comprise about 0.10 second to about 0.125 second.

4. The method of claim 1 wherein the applying comprises alternating pulses of the first plurality of the plurality of pulses with pulses of the second plurality of the plurality of pulses.

5. The method of claim 1 wherein the first electric potential (V 1 ) comprises about 8 volts to about 28 volts, and the second electric potential (V 2 ) comprises about 0.5 volts to about 10 volts.

6. The method of claim 1 wherein the first duration (t 1 ) comprises about 0.25 second, and the second duration (t 2 ) comprises about 0.125 second.

7. The method of claim 1 wherein the nickel-based superalloy comprises about 60 percent nickel, about 10 percent cobalt, about 8 percent to about 14 percent chromium, and about 4 percent to about 10 percent tungsten.

8. The method of claim 1 wherein the electrolyte comprises about a 10 percent to about 30 percent by weight aqueous solution of sodium nitrate.

9. The method of claim 8 , wherein the electrolyte is buffered with sodium hydroxide to a pH of 9.

10. The method of claim 1 wherein the first electric potential (V 1 ) comprises about 8 volts to about 28 volts, the second electric potential (V 2 ) comprises about 0.5 volts to about 10 volts, the first duration (t 1 ) comprises about 0.1 second to about 1 second, and the second duration comprises about 0.01 second to about 0.125 second.

11. The method of claim 10 , wherein the third electric potential (V 3 ) comprises about 0.5 volts and the third duration (t 3 ) comprises about 50 milliseconds.

12. The method of claim 1 , wherein a pulse frequency of the plurality of electric potential pulses is between about 4 Hz and about 20 Hz.

13. The method of claim 1 , wherein moving the electrode and/or the metallic substrate toward each other while applying the first plurality and the second plurality of the plurality of electric potential pulses over the period of time to electrochemically machine a portion of the metallic substrate comprises moving the electrode and/or the metallic substrate to maintain a constant gap between the electrode and the metallic substrate.

14. The method of claim 13 , wherein the constant gap is between about 0.010 inches and about 0.060 inches.

15. The method of claim 1 , wherein the electrode comprises copper and tungsten.

16. The method of claim 1 , wherein the metallic substrate comprises about 60 percent nickel, 14 percent chromium, 10 percent cobalt, 5 percent titanium, 4 percent molybdenum, 4 percent tungsten, 3 percent aluminum, 0.17 percent carbon, 0.015 percent boron, and 0.03 percent zirconium.

17. The method of claim 1 , wherein the metallic substrate comprises about 62 percent nickel, 9.5 percent cobalt, 9.5 percent tungsten, 8.4 percent chromium, 5.5 percent aluminum, 3.05 percent tantalum, and 1.50 percent hafnium.

18. The method of claim 1 , wherein a pressure of the electrolyte is 100 psi.

19. The method of claim 1 , further comprising pumping the electrolyte towards a gap between the electrode and the metallic substrate to flush away a metal removed from the metallic substrate.

20. The method of claim 1 , wherein the third electric potential (V 3 ) maintains chemical activity at a surface of the metallic substrate.

21. A method for electrochemical machining a metallic workpiece comprising a metallic substrate to form a turbine blade, the method comprising:
applying a plurality of electric potential pulses over a period of time to cause current flow between an electrode and the metallic substrate having an electrolyte between the electrode and the metallic substrate, a first plurality of the plurality of electric potential pulses having a first electric potential (V 1 ) and a first duration (t 1 ) to cause current flow in a first direction between the electrode and the metallic s

Assignees

• Gen Electric

Inventors

• Trimmer Andrew Lee
• COTTRILL John
• Lewis Douglas

Classifications

• C25F3/02 Primary

  Etching · CPC title

• C25F7/00

  Constructional parts, or assemblies thereof, of cells for electrolytic removal of material from objects (for both electrolytic coating and removal C25D); Servicing or operating · CPC title