US4291448A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of restoring the shrouds of turbine blades
Assignee: RTX Corp
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Filing: 1979-04-12
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Granted: 1981-09-29
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Expires: 1999-04-12
Abstract
Abstract A method of restoring the shroud of a turbine blade which has become worn, and particularly those edges of the shroud in the vicinity of what is commonly known as the Z-notch, which comprises the steps of grinding down the shroud in the vicinity of said notch to an accurately predetermined dimension with respect to the original geometry of the shroud, placing the blade in a fixture having a masking member with a slot in it, such that the Z-notch of the blade is disposed substantially in alignment with the slot, and depositing, by means of a plasma spray, a metal alloy onto those edges in an amount just sufficient to build up the same essentially to their original dimensions. Following the plasma spraying, the built-up edges are sintered at a temperature on the order of 1900° F. or more, to more firmly bond the built-up layer to the base metal. The blade is then cooled. The resulting edges conform so closely to the original geometry of a new blade that no additional refinishing or grinding operations are normally required after the sintering.
Inventors
- 👤 Salvatore J. Cretella
- 👤 Matthew Bernardo
- 👤 Ralph T. DeMusis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 08:24
CPC Classifications
B; B23; B23P; B23P6/00; B23P6/002; B23P6/007; F; F01; F01D; F01D5/00; F01D5/005; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49316; Y10T29/49318; Y10T29/49718; Y10T29/49721; Y10T29/49723; Y10T29/49725; Y10T29/49726; Y10T29/49728; Y10T29/49746; Y10T29/4998; Y10T29/49982; Y10T29/49986
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
186 words
The method of repairing worn turbine blades which are originally cast to a predetermined geometry, and formed of a metal selected from the group consisting of nickel-based and cobalt-based alloys, comprising the steps of grinding down to an accurately predetermined dimension, with respect to a predetermined but no longer existing original finished geometry of the shroud thereof, any of the worn, undersized edges of the Z-notch portion of the mounting shroud at one end of the blade, masking the shroud on both sides of said edge after the grinding thereof, subjecting said ground-down edge to a plasma stream comprising essentially a metal selected from the group consisting of nickel-based and cobalt-based alloys, said plasma stream having essentially the same composition as that of the turbine blade being repaired and being applied to an extent which is just sufficient to build up said edge substantially to its original overall finished dimension, such that the added alloy and the metal of the blade become essentially homogeneous and of similar composition, and thereafter sintering said blade at elevated temperatures for a predetermined length of time to season the repair.
Claim 2
Independent Claim
186 words
The method of repairing worn turbine blades which are originally cast to a predetermined geometry, and formed of a metal selected from the group consisting of nickel-based and cobalt-based alloys, comprising the steps of grinding down to an accurately predetermined dimension, with respect to a predetermined but no longer existing original finished geometry of the shroud thereof, any of the worn, undersized edges of the Z-notch portion of the mounting shroud at one end of the blade, masking the shroud on both sides of said edge after the grinding thereof, subjecting said ground-down edge to a plasma stream comprising essentially a metal selected from the group consisting of nickel-based and cobalt-based alloys, said plasma stream having essentially the same composition as that of the turbine blade being repaired and being applied to an extent which is just sufficient to build up said edge substantially to its original overall finished dimension, such that the added alloy and the metal of the blade become essentially homogeneous and of similar composition, and thereafter sintering said blade at elevated temperatures for a predetermined length of time to season the repair.
Claim 3
Dependent Claim
20 words
The method of claim 1, wherein the sintering is carried out at a temperature on the order of 1975° F.
Claim 4
Dependent Claim
16 words
The method of claim 1, wherein the sintering is carried out in an atmosphere containing argon.
Claim 5
Dependent Claim
16 words
The method of claim 1, wherein the sintering is carried out in an atmosphere containing hydrogen.
Claim 6
Dependent Claim
26 words
The method of claim 1, and including the further steps of cooling the blade after sintering, at a rate essentially not appreciably less than 35° F./minute.
Claim 7
Dependent Claim
34 words
The method of claim 1, wherein the step of subjecting the ground-down edge to the plasma stream comprises spraying the metal alloy against said edge with a particle velocity in excess of supersonic speed.
Claim 8
Dependent Claim
38 words
The method of claim 1, wherein the step of subjecting the ground-down edge to the plasma stream comprises spraying the metal alloy against said edge with a particle velocity on the order of twice the speed of sound.
Claim 9
Dependent Claim
30 words
The method of claim 1, wherein the step of subjecting the ground-down edge to the plasma stream comprises spraying the edge with a molten alloy having substantially quantities of chromium.
Claim 10
Dependent Claim
33 words
The method of claim 1, wherein the step of subjecting the ground-down edge to the plasma stream comprises spraying the edge with a molten alloy containing silicon not in excess of several percent.
Claim 11
Dependent Claim
27 words
The method of claim 1, wherein the step of masking the shroud comprises placing a housing around those portions of the edge which are to be built-up.
Claim 12
Dependent Claim
31 words
The method of claim 1, wherein the step of masking the shroud comprises placing a slotted metal plate in front of the portion of the edge which is to be built-up.
Claim 13
Dependent Claim
14 words
The method of claim 1, wherein the metal alloy of the blades contains nickel.
Claim 14
Dependent Claim
15 words
The method of claim 12, wherein the metal alloy of the plasma stream contains nickel.
Claim 15
Dependent Claim
14 words
The method of claim 1, wherein the metal alloy of the blades contains cobalt.
Claim 16
Dependent Claim
15 words
The method of claim 14, wherein the metal alloy of the plasma stream contains cobalt.
Claim 17
Dependent Claim
25 words
The method of claim 1, and including the further step of de-burring the said one edge of the shroud after it has been ground down.
Claim 18
Dependent Claim
66 words
The method of claim 1, and including the further steps of grinding down to an accurately predetermined dimension one edge of the other Z-notch portion of the mounting shroud, masking the shroud on both sides of the immediately preceding edge after the grinding thereof, and subjecting it to a plasma stream containing a metal alloy so a s to build it up to its original dimension.
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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) | 1984-09-28 | 1985-03-30 | 1985-09-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-09-28 | 1989-03-30 | 1989-09-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-09-28 | 1993-03-30 | 1993-09-29 | $7700.00 | Window Closed / Lapsed |