Method for the electroplating of TiAl alloys

Patent metadata

Field	Value
Publication number	US-10081877-B2
Application number	US-201615193688-A
Country	US
Kind code	B2
Filing date	Jun 27, 2016
Priority date	Jul 14, 2015
Publication date	Sep 25, 2018
Grant date	Sep 25, 2018

Abstract

The present invention relates to a method for the coating of a surface of a TiAl alloy, in which at least one layer is electroplated on the surface of the TiAl alloy, wherein the surface of the TiAl alloy is subjected to an at least two-step surface treatment for the formation of a roughened surface, this treatment comprising at least one electrochemical processing and at least one electroless chemical processing.

First claim

What is claimed is:

1. A method for coating a surface of a TiAl alloy, comprising the steps of:
providing a TiAl alloy having a surface;
roughening the surface of the TiAl alloy in a two-step surface treatment, including:
applying an electrochemical process to the surface; and
treating the surface with an electroless chemical process after the electrochemical process;
wherein the surface of the TiAl alloy is sufficiently roughened after the electrochemical process and electroless chemical process without mechanical roughening of the surface of the TiAl alloy;

chemically activating the surface of the TiAl alloy after roughening the surface of the TiAl alloy in the two-step surface treatment; and
electroplating at least one layer on the surface of the TiAl alloy after the step of chemically activating the surface of the TiAl alloy,
wherein the electrochemical processing is conducted by anodic etching in an acetic acid-hydrofluoric acid solution, wherein concentrations by weight of 800 to 900 g/L of acetic acid and 100 to 200 g/L of hydrofluoric acid are selected for the composition of the acetic acid-hydrofluoric acid solution.

2. The method according to claim 1 , wherein the step of electroless chemical processing is etching the surface of the TiAl alloy with a fluoroboric acid-sodium tetrafluoroborate solution.

3. The method according to claim 1 , further comprising the steps of:
between the electrochemical processing step and the electroless chemical processing step cleaning the surface of the TiAl alloy with compressed air and/or a water jet; and
drying the surface of the TiAl alloy after cleaning the surface.

4. The method according to claim 1 , further comprising the step of:
prior to the two-step surface treatment, chemically etching of the surface of the TiAl alloy with a nitric acid solution containing ammonium bifluoride, wherein, weight concentrations of 300 to 400 g/L of nitric acid and 50 to 80 g/L of ammonium bifluoride are selected for the nitric acid solution.

5. The method according to claim 4 , further comprising the step of:
prior to the step of chemical etching of the surface of the TiAl alloy with the nitric acid solution containing ammonium bifluoride, chemically cleaning the surface with an alkaline cleaning solution.

6. The method according to claim 1 , wherein the step of chemically activating the surface of the TiAl alloy is chemically activating of the surface with a sulfuric acid solution.

7. The method according to claim 1 , further comprising the step of:
rinsing of the surface with demineralized water between and/or after each of the individual processing steps.

8. The method according to claim 1 , wherein a nickel or cobalt layer is deposited as the electroplated layer.

9. The method according to claim 1 , further comprising the step of:
depositing at least one second layer on the electroplated layer.

10. The method according to claim 9 , wherein the at least one second layer is deposited by a method that is selected from the group consisting of electroplating, physical vapor deposition, chemical vapor deposition, thermal spraying, welding, and soldering.

11. The method according to claim 1 , wherein the TiAl alloy further comprises niobium and/or molybdenum as additional components, wherein the niobium content is in the range of 0 to 5 at. % and/or the molybdenum content lies in the range of 0 to 3 at. % and the Al content lies in the range of 40 to 45 at. %, with the remainder being Ti and other additional alloy components.

Assignees

• MTU Aero Engines AG

Inventors

• Richter Sebastian
• Linska Josef

Classifications

• C25D11/26

  of refractory metals or alloys based thereon · CPC title

• C25D11/08

  containing inorganic acids · CPC title

• C25D5/44

  Aluminium · CPC title

• C25F3/02

  Etching · CPC title

• C25D5/38 Primary

  of refractory metals or nickel · CPC title