Corrosion resistant article and methods of making

Patent metadata

Field	Value
Publication number	US-10179943-B2
Application number	US-201414334742-A
Country	US
Kind code	B2
Filing date	Jul 18, 2014
Priority date	Jul 18, 2014
Publication date	Jan 15, 2019
Grant date	Jan 15, 2019

Abstract

An article and method of forming the article are disclosed. The article has a surface comprising a nanostructured ferritic alloy. The surface includes a plurality of nanofeatures that include complex oxides of yttrium and titanium disposed in an iron-bearing alloy matrix. The iron-bearing alloy matrix at the surface includes about 5 weight percent to about 30 weight percent of chromium, and about 0.1 weight percent to about 10 weight percent of molybdenum. Further, a concentration of a chi phase or a sigma phase in the nanostructured ferritic alloy at the surface is less than about 5 volume percent. The method generally includes the steps of milling, thermo-mechanically consolidating, annealing, and then cooling at a rate that hinders the formation of chi and sigma phases in the nanostructured ferritic alloy at the surface.

First claim

The invention claimed is:

1. A method, comprising:
milling an iron-bearing alloy powder in the presence of yttrium oxide until the oxide is substantially dissolved into the alloy;
thermo-mechanically consolidating the powder to form a consolidated component;
annealing the consolidated component to form an annealed component; and
cooling the annealed component at a rapid rate to form a processed component,
wherein the processed component comprises a surface comprising a nanostructured ferritic alloy, the nanostructured ferritic alloy comprising a plurality of nanofeatures disposed in an iron-bearing alloy matrix, the plurality of nanofeatures comprising complex oxide particles, wherein the complex oxide particles comprise yttrium and titanium;
wherein the matrix at the surface comprises about 5 weight percent to about 30 weight percent chromium, and about 0.1 weight percent to about 10 weight percent molybdenum;
wherein a concentration of a chi phase or a sigma phase in the nanostructured ferritic alloy at the surface is less than about 5 volume percent; and
wherein the annealing step is performed at a temperature above the solvus temperature of the chi phase and the sigma phase.

2. The method of claim 1 , wherein the step of thermomechanically consolidating comprises hot isostatic pressing, extruding, forging, compacting, or a combination of any of these.

3. The method of claim 1 , wherein the surface is substantially free of chi phase.

4. The method of claim 1 , wherein the surface is substantially free of sigma phase.

5. The method of claim 1 , wherein cooling the annealed component at a rapid rate comprises cooling at a rate rapid enough to inhibit precipitation of chromium or molybdenum-enriched secondary phases.

6. The method of claim 1 , wherein cooling the annealed component at a rapid rate comprises water quenching the annealed component.

7. The method of claim 1 , wherein the matrix comprises molybdenum in an amount from about 3 weight percent to about 10 weight percent.

8. The method of claim 7 , wherein the matrix comprises molybdenum in an amount from about 6 weight percent to about 10 weight percent.

9. The method of claim 1 , wherein the consolidated component comprises sigma phase.

Assignees

• Gen Electric

Inventors

• Huang Shenyan
• Didomizio Richard
• Rebak Raul Basilio

Classifications

• B22F2003/248

  Thermal after-treatment · CPC title

• B22F3/20

  by extruding · CPC title

• F16C33/121

  Use of special materials · CPC title

• B22F2998/10

  Processes characterised by the sequence of their steps · CPC title

• B22F3/24 Primary

  After-treatment of workpieces or articles {(B22F3/1146 takes precedence)} · CPC title