# US 5,344,510 A · Method for removing sulfur from superalloy articles to improve their oxidation resistance

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 5,344,510 A
- Document ID: US5344510A
- Status: Granted
- Kind: A
- Application number: 08/048,407
- Filed: 1993-04-14
- Granted: 1994-09-06
- Earliest claimed: 1993-04-14
- Assignees: United Technologies Corporation
- Inventors: William P. Allen; Donald R. Parille
- Web page: https://patentgrep.com/patent/US5344510A

## CPC

- C22F 1/10: of nickel or cobalt or alloys based thereon
- C21D 3/02: Extraction of non-metals
- C22B 9/14: Refining in the solid state
- C22F 1/02: in inert or controlled atmosphere or vacuum (adjusting the composition of the atmosphere C21D1/76)
- C22F: CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass, C23F17/00)
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- C22B: PRODUCTION AND REFINING OF METALS (electrolytic C25); PRETREATMENT OF RAW MATERIALS

## Abstract

Superalloy articles are made more oxidation resistant by a process which includes heating the article in an environment having a reduced pressure of inert gas and a low partial pressure of oxygen to a temperature at which the sulfur in the article diffuses out. The heat treatment is best carried out at a temperature within the range defined by the incipient melting temperature of the article and about 150.degree. C. below the incipient melting temperature of the article. Alternatively, the heat treatment may be carried out at a temperature above the gamma prime solvus temperature of the article and below the incipient melting temperature of the article. At such temperatures, sulfur readily diffuses out of the article, and a more oxidation resistant component is produced.

## Claims

### Claim 1

A method for removing sulfur from a nickel base superalloy article comprising the step of heating the article in an environment having a reduced pressure of inert gas and a low partial pressure of oxygen, to a temperature at which sulfur diffuses out of the article.

### Claim 2 (depends on 1)

The method of claim 1, wherein said article is cleaned prior to heat treatment in order to remove any surface oxide which has formed on said article.

### Claim 3 (depends on 1)

The method of claim 1, wherein said environment has a total system pressure within the range of about 10.sup.-6 torr to about 100 torr.

### Claim 4 (depends on 1)

The method of claim 1, wherein said partial pressure of oxygen is no greater than about 2 torr.

### Claim 5 (depends on 1)

The method of claim 1, wherein the article is heated to a temperature within the range defined by the melting temperature of the article and approximately 150.degree. C. below the melting temperature of the article.

### Claim 6 (depends on 1)

The method of claim 1, wherein the sulfur in the article is reduced to below 5 parts per million, by weight.

### Claim 7 (depends on 1)

The method of claim 1, wherein the sulfur in the article is reduced to below 3 parts per million, by weight.

### Claim 8 (depends on 1)

The method of claim 1, wherein the sulfur in the article is reduced to below 1 parts per million, by weight.

### Claim 9

A method for removing sulfur from a nickel base superalloy turbine blade, the blade having a root portion adjacent to an airfoil portion which is thinner than the root portion, comprising the step of heating the airfoil portion in an environment having a reduced pressure of inert gas, a low partial pressure of oxygen, and a total system pressure of about 10.sup.-6 torr to about 100 torr, wherein the airfoil portion is heated to a temperature at which sulfur diffuses out of the airfoil portion; whereby the sulfur in the airfoil portion is reduced to below about 5 parts per million, by weight.