GB2041246A - Improved protective layer - Google Patents
Improved protective layer Download PDFInfo
- Publication number
- GB2041246A GB2041246A GB8002916A GB8002916A GB2041246A GB 2041246 A GB2041246 A GB 2041246A GB 8002916 A GB8002916 A GB 8002916A GB 8002916 A GB8002916 A GB 8002916A GB 2041246 A GB2041246 A GB 2041246A
- Authority
- GB
- United Kingdom
- Prior art keywords
- platinum group
- article according
- layer
- coating
- barrier layer
- 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.)
- Granted
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
- F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
- F01D5/12—Blades
- F01D5/28—Selecting particular materials; Particular measures relating thereto; Measures against erosion or corrosion
- F01D5/288—Protective coatings for blades
-
- 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
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
-
- 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
- C23C4/10—Oxides, borides, carbides, nitrides or silicides; Mixtures thereof
- C23C4/11—Oxides
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Plasma & Fusion (AREA)
- General Engineering & Computer Science (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
- Coating By Spraying Or Casting (AREA)
Abstract
An article e.g. blades in gas turbine engines suitable for use all elevated temperature (up to 1600 DEG C and beyond) comprises a metallic substrate on which is deposited a first coating or layer comprising one or more of the platinum group metals or an alloy including one or more of the platinum group metals on which is deposited a second coating or layer comprising a thermal barrier layer.
Description
SPECIFICATION
Improved protective layer
This invention relates to means for protecting substrates and in particular Ni- and Co-base superalloys from high temperatures, for example temperatures such as typically occur in gas turbine engines.
Improvements in the efficiency of gas turbine engines can in general best be achieved directly or indirectly by an increase in the temperature of the combustion gases incident on the turbine blades.
The main constraint to the achievement of this objective is the limited choice of materials for the blades which will retain adequate strength and corrosion resistance above 1 100"C for sufficient lengths of time. New processing developments for advanced
Ni- and Co-base superalloys have given the engine designer new limits of strength capability at the expense of environmental corrosion resistance.
Simultaneous advances in coating technology have gone some way in achieving a satisfactory balance of materials requirements. However, further increases in gas temperature up to and even beyond 1 6000C are still required. To meet this problem refractory alloys and ceramics must be considered as potential materials for advanced engines or, alternatively, progress towards more sophisticated means of reducing metal temperature, for example by forced cooling, must be made.
Four methods of cooling to reduce metal surface temperature, namely convection, impingement, film and transpiration or effusion cooling, involve elaborate fabrication and machining techniques to produce complex geometry components. Although effective, they all involve an increase in the coolant to gas flow ratio which adversely affects the overall turbine efficiency. An alternative approach to surface cooling, and one which can be termed complementary to existing cooling techniques, is the concept of thermal barrier coating. This technique comprises effectively a transitional technology between a metallic and an all ceramic engine system, and some of the problems associated with ceramics operating in a high temperature, for example thermal cycling and erosion/corrosion-promoting environment, need to be carefully considered when designing such a coating formulation.
The principle of applying a low thermal conductivity ceramic to a metal substrate as a means of thermal insulation has been recognised for some time.
Many of the problems which have arisen in the past have been associated with metal substrate/ceramic compatibility. Differences in thermal expansion between the alloy and oxide invariably cause spallation of the thermal barrier layer. Adhesion of the ceramic composition to the substrate has posed further problems. Many of these initial limitations have been overcome by applying to the substrate a first socalled bond coat, e.g. of Mo, Nichrome or NiCrAIY, followed by the preferred refractory oxide barrier layer, usually comprising some form of stabilised zirconia. Zirconia stabilised with either calcia, hafnia, magnesia or any of the rare earth oxides may be used as a barrier oxide due to its very low thermal conductivity, low density and high melting point.
However, thermal expansion compatibilty with normally used bond-coats is still far from adequate. This fact in general has lead to the development of the so-called graded thermal barrier system where compositional control of the coating from metal or metal/ceramic to ceramic has met with some success. It is preferred, however, to limit the total barrier coating thickness to below 0.020 inches and develop a simple duplex metal-ceramic system.
Further to mechanical problems of bonding ceramics to metals, the questions of chemical compatibility between the oxide and metal bond coat and the rate at which combustion gases can permeate the preferred oxide barrier must be taken into account. In the first case, nickel, nickel-aluminide or
NiCrAIY bond coats are most suitable choices with respect to ZrO2 as nickel oxide does not react in any way with monoclinic or cubic zirconia, although other MCrAIY compositions where M=Fe or Co may be poor second choice bond coat systems because of the significant reaction of cobalt oxide and iron oxide with zirconia.Although chemically inert towards zirconia, under oxidising conditions (normally experienced in gas turbines) nickel oxide NiO oxidises to Ni2 O3 at 400"C and reverts to NiO at approximately 600"C. The volume change which accompanies this reaction can exacerbate ceramic thermal barrier spallation.
We have now found that one or more of the platinum group metals, by which we mean platinum, palladium, rhodium, iridium, ruthenium and osmium, may be used as a layer intermediate the substrate and the refractory oxide barrier layer.
According to the present invention, therefore, an article suitable for use at elevated temperature, for example in a gas turbine engine, comprises a metallic substrate on which is deposited a first coating or layer comprising one or more of the platinum group metals or an alloy including one or more of the platinum group metals on which is deposited a second coating or layer comprising a thermal barrier layer.
Preferably: (i) the substrate material comprises an alloy, for example a Nit, Co or Fe-based superalloy or a refractory alloy, or a refractory metal,
(ii) the said first coating or layer comprises a protective coating composition typically formed from one or more of the platinum group metals and one or more refractory oxide forming elements such as
Ai, Zr, Ti and soon,
(iii) the thickness of the thermal barrier layer is between 250 and 500 microns and
(iv) the thermal barrier layer comprises a stabilized refractory oxide, for example zirconia stabilised with one or more of calcia, hafnia, magnesia, yttria or a rare earth oxide.
Alternatively, the said first coating or layer consists essentially of one or more of the platinum group metals or an alloy thereof having a thickness within the range 2-25 microns, preferably 3-10 microns.
Optionally, articles according to the present invention may further include one or more of the platinum group metals either in combination with the material
of the thermal barrier layer and/or comprising a
further layer (a so-called "overlayer") over the ther
mal barrier layer.
The platinum group metals which we prefer to use
in articles according to the invention are platinum,
rhodium and/or iridium. We have found that these
metals are particularly efficacious due to theirther
mal expansion compatibility with stabilised zirconia
and their low rates of oxygen permeation. Although the platinum group metals react with zirconia under
extreme reducing conditions, the porous structure of
an oxygen permeation through stabilised zirconia
maintain a sufficient oxygen potential at the interface for no chemical interaction to occur.
Similarly, a platinum group metal used as an overlayer on thermal barrier systems provides a barrier to significant combustion gas penetration to the underlying substrate alloy. A further advantage of the overlayer system is the highly reflective nature of the platinum group metals. The high reflectance of the outer skin backed by a low thermal conductivity oxide layer provides a protective system capable of operating in environments where the combustion gas stream may be as high as 1600"C. A platinum group metal overlayer on a turbine blade would also increase the efficiency of the engine in that a very smooth surface would be presented to the combustion gases.
By way of example, a preferred total system may be prepared by (a) depositing on the preferred substrate between 5 and 12 micron of platinum by any of the standard techniques but preferably by fused salt
plating, (b) diffusion bonding the said platinum layer
to the substrate, for example at 700"C for 1 hour in
vacuo, and (c) plasma- orflame-spraying a stabilised
zirconia coating to a depth of between 250 and 500
micron. A further annealing treatment may be given to stress relieve the total coating.
Alternatively, palladium may be used instead of platinum, at a film thickness between 10 and 25 microns, for example, or iridium may be used at a film thickness between say 2 and 7 microns.
A second preferred method would be to (a) apply the platinum group metal bond coat as above to the preferred substrate (b) zirconise and simultaneously diffusion bond the platinum layer to the substrate, e.g. zirconise using a vacuum pack cementation process operating with a pack composition of 90% zirconia, alumina or magnesia. 8% zirconium metal and 2% ammonium chloride activator at a temperature of 1050"C for 1 hour, (c) pre-oxidise the platinumzirconised coating for 1 hour at 800"C and (d) apply the thermal barrier oxide by plasma- orflamespraying. The latter technique produces an initial internally oxidised (ZrO2) cermet type structure upon which is keyed the total stabilised zirconia barrier layer. The effective result is a graded thermal barrier system.
A third method is to apply the total thermal barrier composition by plasma- or flame-spraying sequentially platinum-zirconium powder compositions from at least 98% Pt 2% ZrO2 at the substrate to 100% zirconia at the outer surface. In this instance, e.g. in flame-spraying, a controlled level of oxygen during processing with platinum- zirconium-stabilizer oxide
powder mix can genrate the desired graded insula
tion coating.
Of the many processing techniques available to
those familiar with coatings application, the aim of the present invention is to improve the adherence,
durability and corrosion resistance of a thermal bar
rier system without affecting the prime purpose of
said system, namely to reduce substrate metal surface temperature thus allowing current high temper
ature materials to operate effectively in hotter com
bustion gas streams.
The system so described and the various methods of application involve the use of one or more of the
platinum group metals or alloys as bond coats,
integral metal/ceramic compositions or overlayers to generate effective high temperature insulation coatings.
Although this invention has been described with particular reference to components, for example turbine nozzle guide vanes, turbine blades, combustors and so on, of gas turbine engines, it may also find application in other technologies such as coal gasification, glass processing and oil refining.
Further, although specific reference has been made to the use of the present invention effectively to reduce metal wall temperatures using low thermal conductivity oxides, the methods herein described results in the production of effective erosion resistant coatings which have application not only in the field of gas turbine engines, but also in processing plant equipment where, for example, rapid pumping of abrasive slurries can cause premature failure of components.
Claims (11)
1. An article suitable for use at elevated temperatures including a metallic substrate on which is deposited a first coating or layer comprising one or more of the platinum group metals or an alloy including one or more of the platinum group metals on which is deposited a second coating or layer comprising a thermal barrier layer.
2. An article according to Claim 1 wherein the metallic substrate is made from a metallic material selected from the group consisting of a nickel, cobalt or iron superalloy, a refractory alloy and a refractory metal.
3. An article according to Claim 1 wherein the first coating or layer comprises a protective coating composition selected from the group consisting of at least one platinum group metal and at least one refractory oxide forming element.
4. An article according to Claim 1 wherein the first coating or layer is made from at least one platinum group metal or alloys containing at least one platinum group metal and having a thickness within the range 2 to 25 microns.
5. An article according to Claim 3 or Claim 4 wherein the refractory oxide forming element is selected from the group consisting of Al, Zr and Ti.
6. An article according to Claim 1 wherein the thermal barrier layer comprises a stabilised refractory oxide.
7. An article according to Claim 6 wherein the stabilised refractory oxide is zirconia stabilised with at least one of the oxides calcia, hafnia, magnesia, yttria and the rare earth oxides.
8. An article according to any one of claims 1,6 or 7 wherein the barrier layer has a thickness between 250 and 500 microns.
9. An article according to any preceding claim including an additional layer disposed overthe thermal barrier layer, the additional layer comprising at least one platinum group metal or an alloy containing at least one platinum group metal.
10. An article according to any one of claims 1,6 or 7 wherein the thermal barrier layer also contains one or more platinum group metals.
11. An article according to claim 1 wherein the platinum group metal is selected from the group consisting of platinum, rhodium and iridium.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8002916A GB2041246B (en) | 1979-02-01 | 1980-01-29 | Protective layer |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB7903511 | 1979-02-01 | ||
GB8002916A GB2041246B (en) | 1979-02-01 | 1980-01-29 | Protective layer |
Publications (2)
Publication Number | Publication Date |
---|---|
GB2041246A true GB2041246A (en) | 1980-09-10 |
GB2041246B GB2041246B (en) | 1982-12-01 |
Family
ID=26270417
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB8002916A Expired GB2041246B (en) | 1979-02-01 | 1980-01-29 | Protective layer |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB2041246B (en) |
Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3426201A1 (en) * | 1984-07-17 | 1986-01-23 | BBC Aktiengesellschaft Brown, Boveri & Cie., Baden, Aargau | PROCESS FOR APPLYING PROTECTIVE LAYERS |
EP0230554A1 (en) * | 1985-12-12 | 1987-08-05 | Asea Brown Boveri Aktiengesellschaft | High-temperature protective layer and method of manufacturing the same |
EP0718420A1 (en) * | 1994-12-24 | 1996-06-26 | Rolls Royce Plc | A method of applying a thermal barrier coating to a superalloy article and a thermal barrier coating |
WO1996035826A1 (en) * | 1995-05-08 | 1996-11-14 | Alliedsignal Inc. | Porous thermal barrier coating |
EP0792948A1 (en) * | 1996-02-29 | 1997-09-03 | Societe Nationale D'etude Et De Construction De Moteurs D'aviation "Snecma" | Thermal barrier coating with improved underlayer and articles having this thermal barrier coating |
EP0814178A1 (en) * | 1996-06-19 | 1997-12-29 | ROLLS-ROYCE plc | A thermal barrier coating for a superalloy article and a method of application thereof |
US5897947A (en) * | 1995-01-31 | 1999-04-27 | Maschinenfabrik Rieter Ag | Method of coating and thread guiding elements produced thereby |
WO2001088218A1 (en) * | 2000-05-15 | 2001-11-22 | Euromat Gesellschaft Für Werkstofftechnologie Und Transfer Mbh | Method for applying precious metal layer and/or alloy and use thereof |
-
1980
- 1980-01-29 GB GB8002916A patent/GB2041246B/en not_active Expired
Cited By (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3426201A1 (en) * | 1984-07-17 | 1986-01-23 | BBC Aktiengesellschaft Brown, Boveri & Cie., Baden, Aargau | PROCESS FOR APPLYING PROTECTIVE LAYERS |
EP0230554A1 (en) * | 1985-12-12 | 1987-08-05 | Asea Brown Boveri Aktiengesellschaft | High-temperature protective layer and method of manufacturing the same |
EP0718420A1 (en) * | 1994-12-24 | 1996-06-26 | Rolls Royce Plc | A method of applying a thermal barrier coating to a superalloy article and a thermal barrier coating |
US5897947A (en) * | 1995-01-31 | 1999-04-27 | Maschinenfabrik Rieter Ag | Method of coating and thread guiding elements produced thereby |
WO1996035826A1 (en) * | 1995-05-08 | 1996-11-14 | Alliedsignal Inc. | Porous thermal barrier coating |
US5624721A (en) * | 1995-05-08 | 1997-04-29 | Alliedsignal Inc. | Method of producing a superalloy article |
EP0792948A1 (en) * | 1996-02-29 | 1997-09-03 | Societe Nationale D'etude Et De Construction De Moteurs D'aviation "Snecma" | Thermal barrier coating with improved underlayer and articles having this thermal barrier coating |
FR2745590A1 (en) * | 1996-02-29 | 1997-09-05 | Snecma | THERMAL BARRIER COATING WITH IMPROVED UNDERLAYER AND PARTS COATED BY SUCH A THERMAL BARRIER |
US5843585A (en) * | 1996-02-29 | 1998-12-01 | Societe Nationale D'etude Et De Construction De Moteurs D'aviation "Snecma" | Thermal barrier coating with improved sub-layer and parts coated with said thermal barrier |
EP0814178A1 (en) * | 1996-06-19 | 1997-12-29 | ROLLS-ROYCE plc | A thermal barrier coating for a superalloy article and a method of application thereof |
US5942337A (en) * | 1996-06-19 | 1999-08-24 | Rolls-Royce, Plc | Thermal barrier coating for a superalloy article and a method of application thereof |
WO2001088218A1 (en) * | 2000-05-15 | 2001-11-22 | Euromat Gesellschaft Für Werkstofftechnologie Und Transfer Mbh | Method for applying precious metal layer and/or alloy and use thereof |
Also Published As
Publication number | Publication date |
---|---|
GB2041246B (en) | 1982-12-01 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PCNP | Patent ceased through non-payment of renewal fee |