Article with improved coating system and methods of forming the same

Patent metadata

Field	Value
Publication number	US-2017247808-A1
Application number	US-201715443039-A
Country	US
Kind code	A1
Filing date	Feb 27, 2017
Priority date	Feb 26, 2016
Publication date	Aug 31, 2017
Grant date	—

Abstract

A method for forming a coating on a surface of an airfoil is provided, where the airfoil has a leading edge, a trailing edge, a pressure side, and a suction side. The method can include forming a platinum-group metal layer on the surface of the airfoil along at least a portion of the trailing edge, and forming an aluminide coating over the surface of the airfoil of the leading edge, the trailing edge, the pressure side, and the suction side. The leading edge may be substantially free from any platinum-group metal. The method may further include, prior to forming the aluminide coating, forming a bond coating on the surface of the airfoil along the leading edge, and after forming the aluminide coating, forming a thermal barrier coating over the bond coating. A method is also generally provided for repairing a coating on a surface of an airfoil.

First claim

What is claimed is:

1 . A method of forming a coating system on a surface of an airfoil having a leading edge, a trailing edge, a pressure side, and a suction side, the method comprising:
forming a platinum-group metal layer on the surface of the airfoil along at least a portion of the trailing edge; and forming an aluminide coating over the surface of the airfoil of the leading edge, the trailing edge, the pressure side, and the suction side.

2 . The method as in claim 1 , wherein the leading edge is substantially free from any platinum-group metal.

3 . The method as in claim 2 , wherein forming the platinum-group metal layer on the surface of the airfoil along the trailing edge comprises:
masking the leading edge, at least a portion of the pressure side, and at least a portion of the suction side to define a masked region, wherein at least a portion of the trailing edge defines an unmasked area; plating the unmasked area with a platinum-group metal to form the platinum-group metal layer; and thereafter, removing the mask to leave the surface underlying the masked region substantially free from the platinum-group metal.

4 . The method as in claim 1 , wherein the platinum-group metal layer comprises platinum, rhodium, palladium, or a mixture thereof.

5 . The method as in claim 1 , wherein the platinum-group metal layer comprises platinum in at least about 50% by weight.

6 . The method as in claim 1 , wherein the platinum-group metal layer is formed to a thickness of about 1 μm to about 10 μm.

7 . The method as in claim 1 , wherein the aluminide coating over the platinum-group metal layer forms a platinum-group metal aluminide coating.

8 . The method as in claim 7 , wherein the platinum-group metal aluminide coating is about 1% to about 10% of the average thickness of the aluminide coating across the leading edge, the pressure side, and the suction side.

9 . The method as in claim 1 , wherein the aluminide coating is formed to a thickness of about 25 μm to about 100 μm.

10 . The method as in claim 1 , wherein the aluminide coating is formed via aluminiding by pack cementation.

11 . The method as in claim 1 , further comprising:
prior to forming the aluminide coating, forming a bond coating on the surface of the airfoil along the leading edge, wherein the bond coating is formed on the surface of the airfoil only in areas free from platinum.

12 . The method as in claim 11 , wherein the bond coating comprises a NiCr alloy, and wherein the bond coating is formed to a thickness of about 125 μm to about 525 μm.

13 . The method as in claim 11 , further comprising:
after forming the aluminide coating, forming a thermal barrier coating over the bond coating.

14 . The method as in claim 13 , wherein the thermal barrier coating is formed with a taper to transition from the leading edge to the pressure side and to the suction side.

15 . The method as in claim 13 , wherein the thermal barrier coating is formed via plasma spray deposition.

16 . The method as in claim 1 , further comprising:
prior to forming an aluminide coating, heating the platinum-group metal layer to a treatment temperature of about 900° C. to about 1200° C.

17 . A method of repairing a coating on a surface of an airfoil having a leading edge, a trailing edge, a pressure side, and a suction side, the method comprising:
stripping any coating from the surface of the airfoil; forming a platinum-group metal layer on the surface of the airfoil along at least a portion of the trailing edge; and forming an aluminide coating over the surface of the airfoil of the leading edge, the trailing edge, the pressure side, and the suction side.

18 . The method as in claim 17 , wherein the coating was stripped via a chemical stripping process.

19 . The method as in claim 18 , further comprising:
prior to forming an aluminide coating, heating the platinum-group metal layer to a treatment temperature of about 900° C. to about 1200° C. and at a treatment pressure of about 1 torr or less.

20 . A method of forming a coating system on a surface of an airfoil having a leading edge, a trailing edge, a pressure side, and a suction side, the method comprising:
forming a platinum-group metal layer on a first region of the surface of the airfoil leaving a second region substantially free from platinum; heat treating the platinum-group metal layer; thereafter, forming a bond coating over at least a portion of the second region substantially free from platinum on the surface of the airfoil; thereafter, forming an aluminide coating over the entire surface of the airfoil.

Assignees

• Gen Electric

Inventors

• Nagaraj Bangalore Aswatha
• Adavikolanu Siva Ram Surya Sanyasi
• Chomka Michal Stanislaw

Classifications

• C25D5/50

  by heat-treatment · CPC title

• F01D5/005

  Repairing methods or devices · CPC title

• C25D3/50

  of platinum group metals · CPC title

• F05D2240/121

  related to the leading edge of a stator vane · CPC title

• F05D2230/80

  Repairing, retrofitting or upgrading methods · CPC title