US4895201A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Oxidation resistant superalloys containing low sulfur levels
Assignee: RTX Corp
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Filing: 1987-07-07
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Granted: 1990-01-23
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Expires: 2007-07-07
Abstract
Abstract According to this invention, the oxidation resistance of alumina scale forming nickel based superalloys is significantly improved by controlling the level of sulfur in the alloy composition. According to one preferred embodiment of the invention, the superalloys contain less than 5 parts per million, by weight, of sulfur. Most preferably, they contain less than 2 parts per million, by weight, of sulfur.
Inventors
- 👤 Michael A. DeCrescente
- 👤 Norman S. Bornstein
- 👤 John G. Smeggil
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 02:31
CPC Classifications
C; C22; C22C; C22C19/00; C22C19/03; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49316; Y10T29/4932
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
104 words
A method for making an oxidation resistant blade or vane casting for a gas turbine engine, comprising the steps of melting a nickel base superalloy composition selected from the group of compositions which form an alumina scale on the casting surface at elevated temperatures; contacting the molten superalloy with a rare earth compound to form rare earth sulfides; removing said sulfides; and solidifying the molten superalloy to form the metal casting, wherein said removing step is conducted such that the sulfur level in the solidified casting is no more than about 5 parts per million by weight, whereby the casting has improved oxidation resistance.
Claim 2
Independent Claim
104 words
A method for making an oxidation resistant blade or vane casting for a gas turbine engine, comprising the steps of melting a nickel base superalloy composition selected from the group of compositions which form an alumina scale on the casting surface at elevated temperatures; contacting the molten superalloy with a rare earth compound to form rare earth sulfides; removing said sulfides; and solidifying the molten superalloy to form the metal casting, wherein said removing step is conducted such that the sulfur level in the solidified casting is no more than about 5 parts per million by weight, whereby the casting has improved oxidation resistance.
Claim 3
Dependent Claim
29 words
The method of claim 1, wherein said removing step is conducted such that the sulfur level in the casting is no more than 2 parts per million by weight.
Claim 4
Independent Claim
106 words
A method for making an oxidation resistant nickel base superalloy casting, comprising the steps of melting an alumina scale forming composition which consists essentially of, by weight percent, 5-15Cr, 3-10Al, 0-15Co, 0-8Mo, 0-14Ta, 0-5Ti, 0-4Nb, 0-3Hf, 0-2V, 0-0.1Zr, 0-0.3C, 0-0.1B, balance nickel; contacting the molten superalloy with a rare earth compound to form rare earth containing sulfides; removing said sulfides; and solidifying the molten superalloy under conditions which result in a casting containing no intentional additions of rare earth elements, and having a sulfur activity which corresponds to the activity in the same composition which contains no more than about 5 parts per million by weight.
Claim 5
Independent Claim
106 words
A method for making an oxidation resistant nickel base superalloy casting, comprising the steps of melting an alumina scale forming composition which consists essentially of, by weight percent, 5-15Cr, 3-10Al, 0-15Co, 0-8Mo, 0-14Ta, 0-5Ti, 0-4Nb, 0-3Hf, 0-2V, 0-0.1Zr, 0-0.3C, 0-0.1B, balance nickel; contacting the molten superalloy with a rare earth compound to form rare earth containing sulfides; removing said sulfides; and solidifying the molten superalloy under conditions which result in a casting containing no intentional additions of rare earth elements, and having a sulfur activity which corresponds to the activity in the same composition which contains no more than about 5 parts per million by weight.
Claim 6
Dependent Claim
13 words
The method of claim 3, wherein the rare earth compound is yttrium oxide.
Claim 7
Dependent Claim
24 words
The method of claim 3, wherein the molten superalloy is directionally solidified to make a casting having a columnar grain or single crystal microstructure.
Claim 8
Dependent Claim
63 words
The method of claim 5, wherein the molten superalloy is directionally solidified using investment casting techniques, and the casting has an internal cavity formed by the steps which include pouring the molten superalloy into a mold which contains a ceramic core, solidifying the superalloy around the core within the mold, and then removing the core from the casting to make a hollow casting.
Claim 9
Dependent Claim
27 words
The method of claim 3, further comprising the step of removing the rare earth sulfides from the molten superalloy prior to said step of solidifying the superalloy.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-01-22 | 1993-07-24 | 1994-01-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-01-22 | 1997-07-24 | 1998-01-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-01-22 | 2001-07-24 | 2002-01-23 | $7700.00 | Window Closed / Lapsed |