GB2025469A - Plasma sprayed MCrAlY coatings - Google Patents
Plasma sprayed MCrAlY coatings Download PDFInfo
- Publication number
- GB2025469A GB2025469A GB7830131A GB7830131A GB2025469A GB 2025469 A GB2025469 A GB 2025469A GB 7830131 A GB7830131 A GB 7830131A GB 7830131 A GB7830131 A GB 7830131A GB 2025469 A GB2025469 A GB 2025469A
- Authority
- GB
- United Kingdom
- Prior art keywords
- coating
- envelope
- mcraiy
- defects
- metallic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 238000000576 coating method Methods 0.000 title claims abstract description 108
- 239000011248 coating agent Substances 0.000 claims abstract description 87
- 230000007547 defect Effects 0.000 claims abstract description 27
- 239000000758 substrate Substances 0.000 claims abstract description 23
- 229910000601 superalloy Inorganic materials 0.000 claims abstract description 17
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 16
- 239000011651 chromium Substances 0.000 claims abstract description 16
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 13
- 229910052751 metal Inorganic materials 0.000 claims abstract description 12
- 239000002184 metal Substances 0.000 claims abstract description 12
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 11
- 239000011148 porous material Substances 0.000 claims abstract description 9
- 238000007750 plasma spraying Methods 0.000 claims abstract description 7
- 239000004411 aluminium Substances 0.000 claims abstract description 4
- 230000035515 penetration Effects 0.000 claims abstract description 4
- 238000003825 pressing Methods 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 20
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 18
- 230000001681 protective effect Effects 0.000 claims description 11
- 238000007789 sealing Methods 0.000 claims description 11
- 229910052759 nickel Inorganic materials 0.000 claims description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 6
- 239000011888 foil Substances 0.000 claims description 5
- 238000001513 hot isostatic pressing Methods 0.000 claims description 5
- 229910017052 cobalt Inorganic materials 0.000 claims description 4
- 239000010941 cobalt Substances 0.000 claims description 4
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 238000009713 electroplating Methods 0.000 claims 2
- 238000009792 diffusion process Methods 0.000 claims 1
- 230000002708 enhancing effect Effects 0.000 claims 1
- 230000000149 penetrating effect Effects 0.000 claims 1
- 229910045601 alloy Inorganic materials 0.000 abstract description 8
- 239000000956 alloy Substances 0.000 abstract description 8
- 238000005260 corrosion Methods 0.000 abstract description 8
- 150000002739 metals Chemical class 0.000 abstract description 3
- 239000007921 spray Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 4
- 230000002411 adverse Effects 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 238000007740 vapor deposition Methods 0.000 description 2
- 239000007832 Na2SO4 Substances 0.000 description 1
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 1
- 239000005030 aluminium foil Substances 0.000 description 1
- 239000000306 component Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 235000011152 sodium sulphate Nutrition 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 238000004544 sputter deposition Methods 0.000 description 1
- 238000005486 sulfidation Methods 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
- C23C4/06—Metallic material
- C23C4/073—Metallic material containing MCrAl or MCrAlY alloys, where M is nickel, cobalt or iron, with or without non-metal elements
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Plasma & Fusion (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Coating By Spraying Or Casting (AREA)
Abstract
The oxidation-corrosion resistance of plasma sprayed MCrAlY overlay coatings is improved. The coating method involves plasma spraying the MCrAlY coating alloy onto a superalloy substrate, applying a chromium or aluminium envelope over the outer surface of the coating or mechanically working the outer surface to seal the surface against penetration by the high pressure isostatic atmosphere to be subsequently applied and then hot isostatically pressing the coated substrate to close the coating defects and diffuse at least a portion of the envelope, is present, into the overlay coating. The invention thus can provide an MCrAlY coating not only substantially free of pores, voids and the like defects but also having at least an outer zone enriched in chromium, aluminium, or like metals.
Description
SPECIFICATION
Improved plasma sprayed MCrAIY coating and coating method
The present invention relates to high temperature coating of the MCrAIY type and their application to superalloy substrates, particularly by plasma spray techniques.
It is well known that the family of high temperature, oxidation-corrosion resistant coatings commonly referred to as MCrAIY coatings can markedly extend the service life of gas turbine blades, vanes and like compo
nents; for example, see U.S. Patents to Evans et al U.S. 3676085; Goward et al U.S.
3754903 and Talboom Jr. et al U.S.
3 542 530, all of which are of common assignee with the present invention. The MCrAIY coatings are referred to as overlay coatings denoting the fact that they are deposited on the substrate as an alloy and act substantially independently of the substrate in providing oxidation-corrision protection.
In the past, these coatings have been applied to superalloy substrates by vacuum vapor deposition, sputtering and plasma spraying techniques. Of the three, plasma spraying exhibits greatest versatility in manufacturing operations. However, in plasma spraying
MCrAIY coating alloys on superalloy substrates, the prior art has experienced less than satisfactory results due to the development of interconnected as well as isolated pores, voids and like defects in the coating, some of which extend to and penetrate the outer or free surface of the coating. It has been observed that such defects adversely affect the oxidation-corrosion resistance of MCrAIY coatings, for example, as compared to that of similar vapor deposited coatings.
Accordingly, the present invention has one of its objects a plasma spray coated superalloy article and method for coating same wherein the MCrAIY overlay coating is characterized as being substantially free of pores, voids and like defects internally and at the free surface thereof. Another object of the invention is to provide a plasma sprayed MCrAIY coating having oxidation-corrosion resistance at least comparable to that of vapor deposited coatings of the same composition.
The method of the present invention typically envisions a) plasma spraying and
MCrAIY coating alloy onto the superalloy substrate, the coating having the aforementioned defects usually associated with that coating technique, b) sealing the outer or free surface of the MCrAIY coating to prevent penetration of the high pressure isostatic atmosphere to be subsequently applied, and c) hot isostatically pressing the coated substrate to close and collapse the coating defects, thereby improving the protective ability of the coating. In one preferred version, sealing of the outer surface of the plasma sprayed coaing is effected by peening with fine glass frit.In another preferred version, sealing of the outer or free coating surface is effected by providing a metallic envelope thereon, the envelope preferably comprising a metal, such as chromium, aluminum and the like, having the ability to enhance the oxidation-corrosion resistance of the MCrAIY coating. During hot isostatic pressing, a portion, preferably all, of such metallic envelope is diffused into the overlay coating to provide at least an outer zone enriched in chromium, aluminium and the like which, in combination with the substantial absence of coating defects, results in a significantly improved plasma sprayed MCrAIY overlay coating.
These and other objects and advantages of the present invention will become more apparent from the following description of the drawings and preferred embodiment.
Figure 1 is a photomicrograph of plasma sprayed CoCrAIY overlay coating showing defects associated with conventionally applied coatings (100 x before reduction).
Figure 2 is a selected portion of Fig. 1 (500
X before reduction).
Figure 3 is a photomicrograph of a plasma sprayed CoCrAIY overlay coating applied in accordance with the invention (100 X before reduction).
Figure 4 is a selected portion of Fig. 3 (500
X before reduction).
Although the exemplary embodiment of the invention set forth in detail hereinbelow relates to a plasma sprayed CoCrAIY overlay coating on a nickel base superalloy substrate, it is offered merely for illustration and is not intended to limit the scope of the present invention. The invention has general applicability to the family of high temperature coatings designated MCrAIY overlay coatings wherein M is selected from nickel, cobalt and iron and combinations thereof and to the family of metals and alloys referred to as superalloys including, but not limited to, high strength nickel-base, cobalt-base and iron-base alloys.
Referring to Figs. 1 and 2, a CoCrAIY overlay coating of composition, by weight, 65.5% Co, 22.0%Cr, 12.0% Al and 0.5% Y is shown on a nickel base superalloy substrate (the superalloy being commonly known as
B-1900 having a nominal composition of 8.0% Cr, 10.0% Co, 1.0% Ti, 6.0% Al, 6.0% Mo, 4.3% Ta, balance essentially nickel) after conventional plasma spraying, such as after spraying with a spray gun designated SG-100 manufactured by Plasmadyne
Inc. The separation visible between the overlay coating and the substrate occurred during metallographic preparation and should be ignored.It is apparent from the figures that the conventional plasma sprayed CoCrAIY coating contains numerous pores of voids (arrows), both isolated and interconnected, some of which extend to and penetrate the outer or free exposed to the corrosive environment.
Corrosion tests have shown that CoCrAIY overlay coatings of the type shown in Figs. 1 and 2 are inferior in service life to the same coating applied by vacuum vapor deposition techniques. For example, for the same Co
CrAIY coating alloy, the service life of plasma sprayed coatings has been found to be approximately 60% that of vapor deposited coatings in corrosive environments such as sulfidation tests (high temperature Na2SO4 tests).
The present invention improves the oxidation-corrosion resistance of plasma sprayed
MCrAIY overlay coatings by a unique coating method involving a series of steps as set forth immediately below. According to the invention, the nickel base superalloy substrate is plasma sprayed with the CoCrAIY coating alloy in the conventional manner, e.g., with the spray gun designated SG-100 mentioned above. Of course, this overlay coating contains numerous defects in the form of pores or voids, Figs. 1 and 2, which defects adversely affect the protective ability of the coating.
Then, the outer of free surface of the CoCrAIY coating is sealed to prevent penetration of the high pressure isostatic atmosphere to be subsequently applied. In one preferred embodiment of the invention, the outer coating surface is peened or otherwise compressively worked to close the defects which penetrate that surface, thereby providing an outer skin or envelope through which the isostatic atomsphere cannot pass. Glass frit, such as - 40 to + 80 mesh, has been found to provide suitable sealing action when directed against the outer CoCrAIY coating surface with a force represented by 1 ON. Of course the peening material and force with which it is directed against the outer surface are adjusted as desired to achieve the proper sealing action.
In another embodiment, the outer or free surface of the CoCrAIY coating is electroplated or otherwise conveniently coated or wrapped to provide a metallic envelope thereon. Although the metallic envelope may be of any metal which is innocuous to the properties of the overlay coating, such as nickel, cobalt and the like, the envelope is preferably formed of chromium, aluminum or other similar metals which enhance the protective properties of the overlay coating. The metallic envelope is applied in such a manner that the envelope spans or bridges the coating defects which penetrate the free surface and seals them against the high pressure atmosphere to be subsequently applied. The thickness of the metallic envelope can be varied as desired from less than 0.1 mil to more than 3 mils.
An electro-deposited chromium envelope of 1 mil average thickness has been found suitable for use with the CoCrAIY coating and the nickel base superalloy substrate described above. If a wrapping technique is used, metal foil for example, aluminum foil may be satisfactorily used in the invention.
After proper outer surface sealing is achieved, the coated substrate or article is hot isostatically pressed to close the pores, voids and other defects of the CoCrAIY coating. The parameters of hot isostatic pressing can be varied to suit particular needs; times less than one hour to more than five hours, temperatures less than 1 600 F to more than 21 00 F and pressures less than 10 ksi to more than 30 ksi being useful. Preferably, however, if a metallic envelope is utilized, the pressing parameters are sufficient not only to close the defects in the CoCrAIY coating but also to diffuse at least a portion of the metallic envelope into the overlay coating to further improve its protective properties. Preferably, the entire envelope is diffused into the coating to provide maximum coating protectiveness.For the chromium envelope of 1 mil thickness, hot isostatic pressing for four hours at 1 950 F and 1 5 ksi was found suitable for closing substantially all the voids or defects associated with the coating and also for diffusing the chromium envelope completely into the outer zone of the coating. The resulting defect-free, chromium enriched CoCrAIY coating is shown in Figs. 3 and 4. It is apparent from these figures that the CoCrAIY coating is substantially free of pores, voids or other defects and is fully bonded to the superalloy substrate.
If aluminium foil is wrapped or otherwise provided in envelope form on the outer coating surface, the aluminum will melt and diffuse during hot isostatic pressing to form intermetallic compounds with the substrate, for example, NiAI, which compounds will enhance the oxidation resistance of the coating and fill-in and close the surface defects.
Those skilled in the art will recognize that the coated article produced in accordance with the present invention will exhibit a service life in corrosive environments, such as that present in gas turbine engines, significantly longer than the same article which is conventionally plasma spray coated. Experiments have shown that the oxidation-corrosion resistance of the MCrAIY overlay coating of the present invention is at least comparable to that of vapor deposited coatings of the same composition. By utilizing a chromium, aluminum, or similar metallic envelope during hot pressing and diffusing a portion or all of the envelope into the coating, the protective properties of the overlay coating can be further improved and varied as desired. Also, a plurality of individual envelopes deposited one upon the other may be employed if it is desired to further alter the overall coating properties.
Although the invention has been shown and described with respect to a preferred embodiment thereof, it should be understood by those skilled in the art that various changes and omissions in the form and detail thereof may be made therein without departing from the scope of the invention.
Claims (11)
1. A method for coating a superalloy substrate with a protective MCrAIY coating where
M is selected from the group consisting of nickel, cobalt and iron, characterized in comprising the steps of:
a) plasma spraying the MCrAIY coating onto the superalloy substrate, the coating being characterized as having pores, voids and similar defects, some of which extend to the free surface of the coating, said defects reducing the protectiveness of the coating.
b) sealing the free surface of the MCrAIY coating to prevent penetration of the high pressure isostatic atmosphere to be subsequently applied.
c) hot isostatically pressing the coated substrate to close the defects of the MCrAIY coating and thereby substantially increase its protective quality.
2. The method according to claim 1, characterized in that sealing is effected by covering the free surface with a metallic envelope.
3. The method of claim 2, characterized in that the envelope comprises a metal which enhances the protective properties of the
MCrAIY coating.
4. The method of claim 3, characterized in that hot isostatic pressing is conducted for a sufficient time and at a sufficient temperature to not only close said defects but also diffuse at least a portion of said metallic envelope into the MCrAIY coating to enhance its protective properties.
5. The method of claim 3, characterized in that the metallic envelope is selected from the group consisting of chromium and aluminium.
6. The method of claim 2, characterized in that the free surface of the MCrAIY coating is covered with the metallic envelope by electro plating a metallic coating thereon.
7. The method of claim 1, characterized in that sealing is effected by peening the free surface of the coating, said peening providing sealing action by closing the defects penetrating said free surface.
8. The method according to claim 1, characterized in that the free surface of the
MCrAIY coating is sealed by providing a metallic envelope thereover, said envelope spanning and sealing the defects which extend to the free surface of the coating and comprising a metal which enhances the protective properties of the MCrAIY coating; and the coated substrate is hot isostatically pressed at a sufficient pressure and temperature and for a sufficient time to close the defects internal of the MCrAIY coating and those intersecting said free surface and to diffuse at least a portion of the metallic envelope into the
MCrAIY coating, closure of said defects and diffusion of said metal envelope into the coating significantly enhancing the protective properties of the coating.
9. The method of claim 8, characterized in that the metallic envelope is provided by wrapping metallic foil thereon.
1 0. The method of claim 9, characterized in that the foil is aluminum foil.
11. The method of claim 8, characterized in that the metallic envelope is provided by electroplating the free surface to deposit a metallic coating thereon.
1 2. The method of claim 11, characterized in that the metallic coating is chromium.
1 3. A coated article, characterized in comprising:
a) a superalloy substrate;
b) a plasma sprayed MCrAIY coating thereon where M is selected from the group consisting of nickel, cobalt, and iron, said coating being characterized as substantially free of pores, voids and similar defects internally and at the free surface thereof 1 4. A coated article, according to claim 13, characterized in further comprising a metallic envelope on said MCrAIY coating, the envelope comprising a metal which enhances the protectiveness of the MCrAIY coating, at least a portion of the envelope being diffused into the coating.
1 5. The article of claim 14, characterized in that the metallic envelope is chromium.
1 6. A coated article, according to claim 13, characterized in having at least an outer zone enriched in a metal which enhances the protectiveness of the MCrAIY coating.
1 7. The article according to claim 13, characterized in that the metal is selected from the group consisting of chromium and aluminum.
1 8. A method of coating a superalloy substrate substantially as herein described with reference to the accompanying drawings.
1 9. A coated article constructed and arranged substantially as herein described and shown in Figs. 3 and 4 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7830131A GB2025469A (en) | 1978-07-17 | 1978-07-17 | Plasma sprayed MCrAlY coatings |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7830131A GB2025469A (en) | 1978-07-17 | 1978-07-17 | Plasma sprayed MCrAlY coatings |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2025469A true GB2025469A (en) | 1980-01-23 |
Family
ID=10498474
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7830131A Withdrawn GB2025469A (en) | 1978-07-17 | 1978-07-17 | Plasma sprayed MCrAlY coatings |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2025469A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2154614A (en) * | 1984-02-22 | 1985-09-11 | H I P | Densified coatings by application of direct fluid pressure |
| US4687678A (en) * | 1984-03-30 | 1987-08-18 | Lindblom Yngve S | Process for preparing high temperature materials |
| DE3810851A1 (en) * | 1988-03-30 | 1989-10-12 | Thyssen Guss Ag | METHOD FOR PRODUCING MOLDED PARTS |
| US6231651B1 (en) | 1999-06-18 | 2001-05-15 | Mississippi State University | Enhanced wood preservative composition |
-
1978
- 1978-07-17 GB GB7830131A patent/GB2025469A/en not_active Withdrawn
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2154614A (en) * | 1984-02-22 | 1985-09-11 | H I P | Densified coatings by application of direct fluid pressure |
| US4687678A (en) * | 1984-03-30 | 1987-08-18 | Lindblom Yngve S | Process for preparing high temperature materials |
| DE3810851A1 (en) * | 1988-03-30 | 1989-10-12 | Thyssen Guss Ag | METHOD FOR PRODUCING MOLDED PARTS |
| US6231651B1 (en) | 1999-06-18 | 2001-05-15 | Mississippi State University | Enhanced wood preservative composition |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |