Chromium-enriched diffused aluminide

Patent metadata

Field	Value
Publication number	US-2016017481-A1
Application number	US-201514792721-A
Country	US
Kind code	A1
Filing date	Jul 7, 2015
Priority date	Jul 18, 2014
Publication date	Jan 21, 2016
Grant date	—

Abstract

A method of applying a protective coating to an article comprises the steps of a) depositing aluminum in a surface region of an article, and b) depositing chromium is the surface region of the article subsequent to step a), whereby at least a portion of the chromium replaces at least a portion of the aluminum. Another method and an article are also disclosed.

First claim

What is claimed is:

1 . A method of applying a protective coating to an article, comprising the steps of:
a) depositing aluminum in a surface region of an article; and b) depositing chromium is the surface region of the article subsequent to step a), whereby at least a portion of the chromium replaces at least a portion of the aluminum.

2 . The method of claim 1 , wherein prior to step b) there is a first amount of aluminum in the surface region of the article, and subsequent to step b) there is a second amount of aluminum in the surface region of the article, the second amount less than the first amount.

3 . The method of claim 1 , wherein at least one of the aluminum and the chromium are deposited by chemical vapor deposition.

4 . The method of claim 2 , wherein the chemical vapor deposition is performed at a temperature of between approximately 1900° F. and 2100° F. (1037.78° C. and 1148.89° C.) for a time of between approximately 1 and 6 hours.

5 . The method of claim 1 , wherein step b) is performed with an activator.

6 . The method of claim 4 , wherein the activator is a halide activator.

7 . The method of claim 1 , wherein step a) results in an aluminum layer between approximately 0.5 and 3.0 mils (0.01 to 0.08 mm) thick.

8 . The method of claim 1 , wherein step b) results in a chromium layer having approximately 20-40% chromium by weight in an outer 30 to 60% of the coating thickness.

9 . The method of claim 1 , wherein step b) results in a chromium layer substantially free of alpha chromium.

10 . A method of applying a protective coating to an article, comprising the steps of:
a) vapor depositing aluminum in a surface region of an article formed of a low-chromium nickel-based alloy; b) vapor depositing chromium in the surface region of the article while removing at least a portion of the aluminum using an activator; and c) heating the article such that the chromium replaces at least a portion of the aluminum through action of the activator.

11 . The method of claim 10 , wherein step c) is performed at a temperature of between approximately 1900° F. and 2100° F. (1037.78° C. and 1148.89° C.) for a time of between approximately 4 and 20 hours.

12 . The method of claim 10 , wherein the activator is a halide activator.

13 . The method of claim 10 , the activator interacts with the aluminum such that chromium replaces the aluminum.

14 . An article, comprising:
a base alloy; a corrosion-resistant coating on the base alloy, the corrosion-resistant coating containing a region of approximately 20%-40% chromium; and an aluminum diffusion zone disposed between the base alloy and the corrosion-resistant coating.

15 . The article of claim 14 , wherein the region extends between a depth of approximately 5 to 60 microns (0.2 to 2.3 mils) from a surface of the coating.

16 . The article of claim 14 , wherein the region is a first region, and further comprising a second region extending from the first region to the aluminum diffusion zone, the second region having a thickness of approximately 0.6 mils (15 microns) and comprising less than approximately 10% chromium by weight.

17 . The article of claim 14 , wherein the aluminum diffusion zone comprises less than approximately 20% chromium by weight.

18 . The article of claim 14 , wherein the article is a turbine blade.

19 . The article of claim 14 , wherein the article comprises external and internal surfaces and wherein the coating is applied to at least one of the external and internal surfaces.

20 . The article of claim 14 , wherein the base alloy is at least one of a nickel-based superalloy and a low-chromium superalloy.

Assignees

• United Technologies Corp

Inventors

• Livings Mark A
• Brown Chelsea

Classifications

• C23C28/00

  Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D · CPC title

• C23C16/0281

  of metallic sub-layers (C23C16/029 takes precedence) · CPC title

• C23C16/08

  from metal halides · CPC title

• C23C10/38

  Chromising · CPC title

• C23C10/10

  Chromising · CPC title