CA2011753A1 - Structural element with protective coating on nickel or cobalt - Google Patents
Structural element with protective coating on nickel or cobaltInfo
- Publication number
- CA2011753A1 CA2011753A1 CA002011753A CA2011753A CA2011753A1 CA 2011753 A1 CA2011753 A1 CA 2011753A1 CA 002011753 A CA002011753 A CA 002011753A CA 2011753 A CA2011753 A CA 2011753A CA 2011753 A1 CA2011753 A1 CA 2011753A1
- Authority
- CA
- Canada
- Prior art keywords
- basic material
- protective coating
- coating
- component
- grain
- 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.)
- Abandoned
Links
- 239000011253 protective coating Substances 0.000 title claims abstract description 30
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 title claims abstract description 27
- 229910017052 cobalt Inorganic materials 0.000 title claims abstract description 12
- 239000010941 cobalt Substances 0.000 title claims abstract description 12
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 title claims abstract description 12
- 229910052759 nickel Inorganic materials 0.000 title claims abstract description 12
- 239000000463 material Substances 0.000 claims abstract description 68
- 238000000576 coating method Methods 0.000 claims abstract description 53
- 239000011248 coating agent Substances 0.000 claims abstract description 38
- 238000005260 corrosion Methods 0.000 claims abstract description 16
- 230000007797 corrosion Effects 0.000 claims abstract description 16
- 230000003647 oxidation Effects 0.000 claims abstract description 16
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 16
- 239000000203 mixture Substances 0.000 claims abstract description 15
- 239000000126 substance Substances 0.000 claims abstract description 14
- 238000009792 diffusion process Methods 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 14
- 239000011651 chromium Substances 0.000 claims description 10
- 239000010936 titanium Substances 0.000 claims description 8
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 7
- 229910052782 aluminium Inorganic materials 0.000 claims description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 7
- 229910052804 chromium Inorganic materials 0.000 claims description 7
- 229910045601 alloy Inorganic materials 0.000 claims description 6
- 239000000956 alloy Substances 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 6
- 238000007750 plasma spraying Methods 0.000 claims description 6
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 5
- 239000013078 crystal Substances 0.000 claims description 5
- 229910052719 titanium Inorganic materials 0.000 claims description 5
- 229910052720 vanadium Inorganic materials 0.000 claims description 5
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 238000001020 plasma etching Methods 0.000 claims description 3
- 238000001953 recrystallisation Methods 0.000 claims description 3
- 239000007921 spray Substances 0.000 claims description 3
- 238000007596 consolidation process Methods 0.000 claims description 2
- 238000000227 grinding Methods 0.000 claims description 2
- 238000005480 shot peening Methods 0.000 claims description 2
- 238000005507 spraying Methods 0.000 claims description 2
- 238000003486 chemical etching Methods 0.000 claims 1
- 238000002360 preparation method Methods 0.000 description 6
- 229910000601 superalloy Inorganic materials 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 230000001681 protective effect Effects 0.000 description 4
- 238000001816 cooling Methods 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000009172 bursting Effects 0.000 description 2
- 238000009499 grossing Methods 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000009661 fatigue test Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 150000002910 rare earth metals Chemical class 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 230000035882 stress Effects 0.000 description 1
- 238000005486 sulfidation Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000003878 thermal aging Methods 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical group [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
- 229910001928 zirconium oxide 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
- C23C30/00—Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process
-
- 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
-
- 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
- C23C4/18—After-treatment
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Plasma & Fusion (AREA)
- General Engineering & Computer Science (AREA)
- Coating By Spraying Or Casting (AREA)
- Turbine Rotor Nozzle Sealing (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
Abstract
Abstract The present invention relates to a component of a basic material based on nickel or cobalt, which has a coating to provide it with protection against oxidation, corrosion, and thermal fatigue, the protective coating and the basic material being of the same chemical composition. This enhances the adhesion of the protective coating, reduces the tendency to crack, and improves its resistance to thermal fatigue.
Description
20117~3 The present invention relates to a component of a basic material that is based on nickel or cobalt, which has a coating to protect it against oxidation, corrosion, and thermal fatigue.
Super alloys that are resistant to high temperatures, and are based on nickel or cobalt, were developed for use in turbine construction. The material used in the blades is exposed to particularly high stress levels; the blades have to be able to withstand not only the high temperatures (in excess of 950C) within the turbine, but must also possess a high level of creep resistance. In order to ensure a higher order of creep resistance, the material used for the blades is grown with large crystals and in part with a columnar structure, from super alloys, by suitable casting and crystallization techniques. It is a disadvantage for corrosion resistance that during this growth, grain boundary deposits of easily oxidized alloy additives, such as vanadium or titanium, for example, are formed. This causes a disadvantageous deterioration of the surface properties such as resistance to oxidation and corrosion, as well as resistance to thermal fatigue. For this reason, coatings such as the MCrAlX,Y
family have been developed (metal, chromium, aluminum, X =
rare earths, Y = yttrium); these improve the surface properties by virtue of their high chromium and aluminum contents which, for their part, form stable oxides during operation of the turbine, and which, as a result of the rare earth metals, improve the adhesion of the oxide layer to the surface coating.
Diffusion processes are disadvantageous because of the different concentrations on both sides of the boundary layer between the coating surface and the coating, which lead to diffusion pores in the area close to the boundary layers, so that the protective coating bursts when thermal stresses are superimposed on points with higher densities of diffusion pores. Furthermore, the MCrAlX,Y coatings have a tendency to 20117~s~
thermal fatigue since there is a disparity in the thermal expansion behaviour between the basic material alloy and the MCrAlYX coating, and the MCrAlX,Y coatings are extremely ductile in comparison to the basic material.
A further known technical solution is the formation of chromium and/or aluminum-rich diffusion coatings on the surface of the basic material by powder pack cementing and/or gas diffusion coating. Coatings of this kind form oxidation-resistant intermetallic phases with the basic material.
Because of the increased hardness of these coatings with intermetallic phases, the fatigue limit of the components is disadvantageously reduced by up to 30 per cent. Since the thermal expansion behaviour is not adapted to the basic material, there is an increased risk of microcracks forming in the component, and this increases with increased thickness of the coating. For this reason, and most disadvantageously, the thickness of the coatings must be kept below 100 ~m.
In the case of the known coatings, components of the basic material that are sensitive to oxidation and corrosion, such as vanadium and titanium, are not used, and stable oxide-forming substances such as aluminum, up to 20 per cent, for example, and chromium up to 40 per cent, are added to form alloys. Matching the composition of the coating to the super-alloy based on cobalt or nickel that is to be coated becomes increasingly involved and more extensive in order to overcome problems of adhesion or to minimize diffusion processes, or to build up protective stable oxides on the surface.
It i~ an object of the present invention to describe a component produced from a basic material based on cobalt or nickel and with a protective coating, that displays greater resistance to thermal fatigue, oxidation, and corrosion at temperatures above 800C, than formerly known coatings and which overcomes the disadvantages of such coatings, and a process for producing such components.
This has been achieved in that the basic material and the protective coating are of the same chemically equal material, and the protective coating is structured with a much finer grain.
According to the present invention there is provided in a component of a basic material based on nickel or cobalt, with a protective coating of the same chemical composition to ensure protection against oxidation, corrosion, and thermal fatigue, the improvement wherein the protective coating is essentially structure with a finer grain than the basic material, and the lowest layer of the fine-grain coating exhibits the same crystal orientation as the large-volume crystallite of the basic material on the boundaries of the coating.
The present invention solves the problems and the disadvantages as they exist in the prior art, in that the substance for the basic material is used for a coating of a similar type, so that there are no diffusion processes and problems of adhesion do not occur when the surface of the basic material is free of oxide. Thus there is no bursting of the particles in the protective coating.
Because of a constant composition of the alloy in the grain volume, an even, stable and protective oxide layer will advantageously be formed on the grain surface when such components are used in an oxidizing flow of hot gas, as in a turbine, for example. Since the grain boundaries of this coating exhibit fewer grain boundary deposits than the basic material, grain boundary corrosion is advantageously reduced. -The preferred corrosion attack at the grain boundaries and the associated tendency to crack, is hindered by the 20117~3 which overcomes the disadvantages of such coatings, and a process for producing such components.
This has been achieved in that the basic material and the protective coating are of the same chemically equal material, and the protective coating is structured with a much finer grain.
According to the present invention there is provided in a component of a basic material based on nickel or cobalt, with a protective coating of the same chemical composition to ensure protection against oxidation, corrosion, and thermal fatigue, the improvement wherein the protective coating is essentially structure with a finer grain than the basic material, and the lowest layer of the fine-grain coating exhibits the same crystal orientation as the large-volume crystallite of the basic material on the boundaries of the cvating.
The present invention solves the problems and the disadvantages as they exist in the prior art, in that the substance for the basic material is used for a coating of a similar type, so that there are no diffusion processes and problems of adhesion do not occur when the surface of the basic material is free of oxide. Thus there is no bursting of the particles in the protective coating.
Because of a constant composition of the alloy in the grain volume, an even, stable and protective oxide layer will aclvantageously be formed on the grain surface when such components are used in an oxidizing flow of hot gas, as in a turbine, for example. Since the grain boundaries of this coating exhibit fewer grain boundary deposits than the basic material, grain boundary corrosion is advantageously reduced. ~-The preferred corrosion attack at the grain boundaries and the associated tendency to crack, is hindered by the 20117~3 this reason, the grain volume of the coating is preferably three powers of ten smaller than the grain volume of the basic material.
The grain boundaries of the preferred basic material IN 100 exhibit grain boundary deposits that contain titanium and vanadium, and these form unstable or low-melting point oxides. For this reason, the coating has fewer deposits on the grain boundaries than the basic material, and this advantageously improves resistance to oxidation and corrosion.
A preferred formation of the protective coating is such that the protective coating is a plasma-spray coating that crystallizes with an extremely fine grain and with small number of deposits because of its very high hardening speed.
In addition, present invention provides a process for the production of a component by the following process steps:
a) Surface preparation by removal of the surface of the basic material, this being done to improve adhesion;
b) Coating applied to the basic material by means of plasma spraying with plasma spra~ing material with the chemical composition of the basic material;
c) Epitactic recrystallisation by means of solution heat treatment at temperatures between 1150 and 1250C;
d) After-treatment of the surface of the protective coating 2S by mechanical consolidation for smoothing and strengthening of the surface and/or diffusion coatings to increase resistance to oxidation.
The process has the advantage that it is suitable for mass-production processes.
When increased demands made of the quality of the coating, the surface preparation is effected by plasma etching with argon plasma. This preparation entails the advantage of 201~7~3 freedom from contamination, and is compatible with a low-pressure plasma spraying process, so that both surface preparation and coating of the basic material can be effected on a component element with an assembly procedure. This enhances the quality so no move to another plant is needed, and no time is spent in a normal atmosphere.
In the event that there are increased demands for economy, the surface preparation can be effected by chemical removal, so that a higher throughput can be achieved.
An abrasive jet preparation is advantageously used as surface removal since large area components such a rotor disks can be prepared for subsequent coating by using this process.
In the case of increased demands for quality, coating can be effected by plasma spraying with plasma spraying material of the same chemical composition as the basic material; in the case of large components and/or in the event of higher demands for economy, this can be effected by plasma spraying in an atmosphere of protective gas.
An optimal accumulation of the coating on the basic material is achieved by epitactic recrystallisation at a solution heat treatment temperature between 1150 and 1250C. When this is done, the lowest position of the fine-grain coating recrystallises in the transition zone between the basic material and the coating, in the same crystal orientation as the large volume crystallite of the basic material on the coating boundary, so that intensive denticulation results between the fine-grain coating and the coarse-grain basic material, which greatly increases adhesion compared to conventional coatings of different kinds. Then, the coated components can be cooled from 1000C to 800C at 30C/minute to 80C/minute and subjected to a multi-stage thermal aging processingO
20117~3 For cast components of super-alloys based on nickel or cobalt a two-stage aging process for forming a suitable ~
structure at 1080C to 1120C for 2 hours to 6 hours followed by 900 to 980C for 10 hours to 20 hours, with intermediate cooling at 750C to 800C. This type of thermal treatment regenerates the properties of the basic material that have been altered by the solution heat treatment, and the strength values of the coating are advantageously enhanced thereby.
Mechanical after-treatment of the surface of the protective coating improves the hardness by preferably shot-blasting, as serves to smooth the surface. The smoothing of the surface can also be effected by means of vibratory grinding or Druckfliess processing.
Diffusion coating as an after-treatment of the surface, as is usually applied to the basic material of super-alloys that are based on nickel or cobalt in order to increase long-term resistance to oxidation can advantageously be effected on the fine-grain coating. This entails the advantage that deep diffusions, as they occur along the grain boundary deposits of the basic material, do not occur in the fine-grain coatings with fewer grain-boundary deposits. The diffusion zone in the fine-grain coating is thus more even and homogeneous when doped, for example, with aluminum or chromium, than is possible on the coarse crystalline basic material. When this is done, the chromium doping improves the resistance to oxidation up to temperatures of 850C, and at the same time, brings about enhanced resistance to corrosion caused by sulfidation. Doping with aluminum, for example, increas~s resistance to oxidation at temperatures of up to 1250C.
The following examples of applications for a component and a process represent preferred embodiments of the present invention.
201~7~3 Example of a component:
A low-pressure plasma coating of the same chemical composition, which has a 3-103-times smaller grain volume than the basic material, was applied on a coarse-crystalline turbine blade of IN 100 as the basic material, which was composed as follows:
13 to 17 %-wt Co 8 to 11 %-wt Cr to 6 %-wt Al 4.5 to 5 %-wt Ti 2 to 4 %-wt Mo 0.~ to 1.2 %-wt V
0.15 to 0.2 %-wt C
0.01 to 0.02 %-wt B
0~03 to 0.09 %-wt Zr Remainder Ni During thermal-fatigue testing (test temperature 1050DC) the coated component exhibited a temperature-endurance three times greater than that of the uncoated basic material.
Example of a process In a coarse-crystalline turbine blade of IN 100 as the basic material, composed of the following elements 13 to 17 %-wt Co 8 to 11 %-wt Cr 5 to 6 %-wt ~1 4.5 to 5 %-wt Ti 2 to 4 %-wt Mo 0.7 to 1.2 %-wt V
0.15 to 0.2 % w~ C
0.01 to 0.02 %-wt B
0.03 to 0.09 %-wt Zr 201~
Remainder Ni the surface of the basic material was removed on average to a depth of 0.5 to 10 ~m by means of argon~plasma etching at a pressure of 2 kPa to 4 kPa.
Next, the basic material was coated with plasma spray material of the same chemical composition as the basic material, using plasma spray technology; this was done at a pressure of 4 kP~ and at a temperature of the basic material of 900C, for a period of 120 seconds.
After the removal of the coated turbine blade, epitactic recrysallisation was effected in a high-vacuum oven. To this end, the component was maintained at a solution heat treatment temperature of 1200C for 4 hours, and cooled to 80C at a rate of 60C/minute.
In order to regenerate the strength characteristics of the basic material and to enhance the strength of the coating, a two-state heat treatment was completed in a high vacuum at 1100C for 4 hours and at 950C for 16 hours, with intermediate cooling to 800C at 60C/minute.
After cooling to room temperature, the surface of the component was smoothed and consolidated by shot peening with zirconium oxide pellets 0.5 to 1.0 mm diameter.
Super alloys that are resistant to high temperatures, and are based on nickel or cobalt, were developed for use in turbine construction. The material used in the blades is exposed to particularly high stress levels; the blades have to be able to withstand not only the high temperatures (in excess of 950C) within the turbine, but must also possess a high level of creep resistance. In order to ensure a higher order of creep resistance, the material used for the blades is grown with large crystals and in part with a columnar structure, from super alloys, by suitable casting and crystallization techniques. It is a disadvantage for corrosion resistance that during this growth, grain boundary deposits of easily oxidized alloy additives, such as vanadium or titanium, for example, are formed. This causes a disadvantageous deterioration of the surface properties such as resistance to oxidation and corrosion, as well as resistance to thermal fatigue. For this reason, coatings such as the MCrAlX,Y
family have been developed (metal, chromium, aluminum, X =
rare earths, Y = yttrium); these improve the surface properties by virtue of their high chromium and aluminum contents which, for their part, form stable oxides during operation of the turbine, and which, as a result of the rare earth metals, improve the adhesion of the oxide layer to the surface coating.
Diffusion processes are disadvantageous because of the different concentrations on both sides of the boundary layer between the coating surface and the coating, which lead to diffusion pores in the area close to the boundary layers, so that the protective coating bursts when thermal stresses are superimposed on points with higher densities of diffusion pores. Furthermore, the MCrAlX,Y coatings have a tendency to 20117~s~
thermal fatigue since there is a disparity in the thermal expansion behaviour between the basic material alloy and the MCrAlYX coating, and the MCrAlX,Y coatings are extremely ductile in comparison to the basic material.
A further known technical solution is the formation of chromium and/or aluminum-rich diffusion coatings on the surface of the basic material by powder pack cementing and/or gas diffusion coating. Coatings of this kind form oxidation-resistant intermetallic phases with the basic material.
Because of the increased hardness of these coatings with intermetallic phases, the fatigue limit of the components is disadvantageously reduced by up to 30 per cent. Since the thermal expansion behaviour is not adapted to the basic material, there is an increased risk of microcracks forming in the component, and this increases with increased thickness of the coating. For this reason, and most disadvantageously, the thickness of the coatings must be kept below 100 ~m.
In the case of the known coatings, components of the basic material that are sensitive to oxidation and corrosion, such as vanadium and titanium, are not used, and stable oxide-forming substances such as aluminum, up to 20 per cent, for example, and chromium up to 40 per cent, are added to form alloys. Matching the composition of the coating to the super-alloy based on cobalt or nickel that is to be coated becomes increasingly involved and more extensive in order to overcome problems of adhesion or to minimize diffusion processes, or to build up protective stable oxides on the surface.
It i~ an object of the present invention to describe a component produced from a basic material based on cobalt or nickel and with a protective coating, that displays greater resistance to thermal fatigue, oxidation, and corrosion at temperatures above 800C, than formerly known coatings and which overcomes the disadvantages of such coatings, and a process for producing such components.
This has been achieved in that the basic material and the protective coating are of the same chemically equal material, and the protective coating is structured with a much finer grain.
According to the present invention there is provided in a component of a basic material based on nickel or cobalt, with a protective coating of the same chemical composition to ensure protection against oxidation, corrosion, and thermal fatigue, the improvement wherein the protective coating is essentially structure with a finer grain than the basic material, and the lowest layer of the fine-grain coating exhibits the same crystal orientation as the large-volume crystallite of the basic material on the boundaries of the coating.
The present invention solves the problems and the disadvantages as they exist in the prior art, in that the substance for the basic material is used for a coating of a similar type, so that there are no diffusion processes and problems of adhesion do not occur when the surface of the basic material is free of oxide. Thus there is no bursting of the particles in the protective coating.
Because of a constant composition of the alloy in the grain volume, an even, stable and protective oxide layer will advantageously be formed on the grain surface when such components are used in an oxidizing flow of hot gas, as in a turbine, for example. Since the grain boundaries of this coating exhibit fewer grain boundary deposits than the basic material, grain boundary corrosion is advantageously reduced. -The preferred corrosion attack at the grain boundaries and the associated tendency to crack, is hindered by the 20117~3 which overcomes the disadvantages of such coatings, and a process for producing such components.
This has been achieved in that the basic material and the protective coating are of the same chemically equal material, and the protective coating is structured with a much finer grain.
According to the present invention there is provided in a component of a basic material based on nickel or cobalt, with a protective coating of the same chemical composition to ensure protection against oxidation, corrosion, and thermal fatigue, the improvement wherein the protective coating is essentially structure with a finer grain than the basic material, and the lowest layer of the fine-grain coating exhibits the same crystal orientation as the large-volume crystallite of the basic material on the boundaries of the cvating.
The present invention solves the problems and the disadvantages as they exist in the prior art, in that the substance for the basic material is used for a coating of a similar type, so that there are no diffusion processes and problems of adhesion do not occur when the surface of the basic material is free of oxide. Thus there is no bursting of the particles in the protective coating.
Because of a constant composition of the alloy in the grain volume, an even, stable and protective oxide layer will aclvantageously be formed on the grain surface when such components are used in an oxidizing flow of hot gas, as in a turbine, for example. Since the grain boundaries of this coating exhibit fewer grain boundary deposits than the basic material, grain boundary corrosion is advantageously reduced. ~-The preferred corrosion attack at the grain boundaries and the associated tendency to crack, is hindered by the 20117~3 this reason, the grain volume of the coating is preferably three powers of ten smaller than the grain volume of the basic material.
The grain boundaries of the preferred basic material IN 100 exhibit grain boundary deposits that contain titanium and vanadium, and these form unstable or low-melting point oxides. For this reason, the coating has fewer deposits on the grain boundaries than the basic material, and this advantageously improves resistance to oxidation and corrosion.
A preferred formation of the protective coating is such that the protective coating is a plasma-spray coating that crystallizes with an extremely fine grain and with small number of deposits because of its very high hardening speed.
In addition, present invention provides a process for the production of a component by the following process steps:
a) Surface preparation by removal of the surface of the basic material, this being done to improve adhesion;
b) Coating applied to the basic material by means of plasma spraying with plasma spra~ing material with the chemical composition of the basic material;
c) Epitactic recrystallisation by means of solution heat treatment at temperatures between 1150 and 1250C;
d) After-treatment of the surface of the protective coating 2S by mechanical consolidation for smoothing and strengthening of the surface and/or diffusion coatings to increase resistance to oxidation.
The process has the advantage that it is suitable for mass-production processes.
When increased demands made of the quality of the coating, the surface preparation is effected by plasma etching with argon plasma. This preparation entails the advantage of 201~7~3 freedom from contamination, and is compatible with a low-pressure plasma spraying process, so that both surface preparation and coating of the basic material can be effected on a component element with an assembly procedure. This enhances the quality so no move to another plant is needed, and no time is spent in a normal atmosphere.
In the event that there are increased demands for economy, the surface preparation can be effected by chemical removal, so that a higher throughput can be achieved.
An abrasive jet preparation is advantageously used as surface removal since large area components such a rotor disks can be prepared for subsequent coating by using this process.
In the case of increased demands for quality, coating can be effected by plasma spraying with plasma spraying material of the same chemical composition as the basic material; in the case of large components and/or in the event of higher demands for economy, this can be effected by plasma spraying in an atmosphere of protective gas.
An optimal accumulation of the coating on the basic material is achieved by epitactic recrystallisation at a solution heat treatment temperature between 1150 and 1250C. When this is done, the lowest position of the fine-grain coating recrystallises in the transition zone between the basic material and the coating, in the same crystal orientation as the large volume crystallite of the basic material on the coating boundary, so that intensive denticulation results between the fine-grain coating and the coarse-grain basic material, which greatly increases adhesion compared to conventional coatings of different kinds. Then, the coated components can be cooled from 1000C to 800C at 30C/minute to 80C/minute and subjected to a multi-stage thermal aging processingO
20117~3 For cast components of super-alloys based on nickel or cobalt a two-stage aging process for forming a suitable ~
structure at 1080C to 1120C for 2 hours to 6 hours followed by 900 to 980C for 10 hours to 20 hours, with intermediate cooling at 750C to 800C. This type of thermal treatment regenerates the properties of the basic material that have been altered by the solution heat treatment, and the strength values of the coating are advantageously enhanced thereby.
Mechanical after-treatment of the surface of the protective coating improves the hardness by preferably shot-blasting, as serves to smooth the surface. The smoothing of the surface can also be effected by means of vibratory grinding or Druckfliess processing.
Diffusion coating as an after-treatment of the surface, as is usually applied to the basic material of super-alloys that are based on nickel or cobalt in order to increase long-term resistance to oxidation can advantageously be effected on the fine-grain coating. This entails the advantage that deep diffusions, as they occur along the grain boundary deposits of the basic material, do not occur in the fine-grain coatings with fewer grain-boundary deposits. The diffusion zone in the fine-grain coating is thus more even and homogeneous when doped, for example, with aluminum or chromium, than is possible on the coarse crystalline basic material. When this is done, the chromium doping improves the resistance to oxidation up to temperatures of 850C, and at the same time, brings about enhanced resistance to corrosion caused by sulfidation. Doping with aluminum, for example, increas~s resistance to oxidation at temperatures of up to 1250C.
The following examples of applications for a component and a process represent preferred embodiments of the present invention.
201~7~3 Example of a component:
A low-pressure plasma coating of the same chemical composition, which has a 3-103-times smaller grain volume than the basic material, was applied on a coarse-crystalline turbine blade of IN 100 as the basic material, which was composed as follows:
13 to 17 %-wt Co 8 to 11 %-wt Cr to 6 %-wt Al 4.5 to 5 %-wt Ti 2 to 4 %-wt Mo 0.~ to 1.2 %-wt V
0.15 to 0.2 %-wt C
0.01 to 0.02 %-wt B
0~03 to 0.09 %-wt Zr Remainder Ni During thermal-fatigue testing (test temperature 1050DC) the coated component exhibited a temperature-endurance three times greater than that of the uncoated basic material.
Example of a process In a coarse-crystalline turbine blade of IN 100 as the basic material, composed of the following elements 13 to 17 %-wt Co 8 to 11 %-wt Cr 5 to 6 %-wt ~1 4.5 to 5 %-wt Ti 2 to 4 %-wt Mo 0.7 to 1.2 %-wt V
0.15 to 0.2 % w~ C
0.01 to 0.02 %-wt B
0.03 to 0.09 %-wt Zr 201~
Remainder Ni the surface of the basic material was removed on average to a depth of 0.5 to 10 ~m by means of argon~plasma etching at a pressure of 2 kPa to 4 kPa.
Next, the basic material was coated with plasma spray material of the same chemical composition as the basic material, using plasma spray technology; this was done at a pressure of 4 kP~ and at a temperature of the basic material of 900C, for a period of 120 seconds.
After the removal of the coated turbine blade, epitactic recrysallisation was effected in a high-vacuum oven. To this end, the component was maintained at a solution heat treatment temperature of 1200C for 4 hours, and cooled to 80C at a rate of 60C/minute.
In order to regenerate the strength characteristics of the basic material and to enhance the strength of the coating, a two-state heat treatment was completed in a high vacuum at 1100C for 4 hours and at 950C for 16 hours, with intermediate cooling to 800C at 60C/minute.
After cooling to room temperature, the surface of the component was smoothed and consolidated by shot peening with zirconium oxide pellets 0.5 to 1.0 mm diameter.
Claims (10)
1. In a component of a basic material based on nickel or cobalt, with a protective coating of the same chemical composition to ensure protection against oxidation, corrosion, and thermal fatigue, the improvement wherein the protective coating is essentially structure with a finer grain than the basic material, and the lowest layer of the fine-grain coating exhibits the same crystal orientation as the large-volume crystallite of the basic material on the boundaries of the coating.
2. A component as claimed in claim 1, wherein the protective coating exhibits fewer grain-boundary deposits and a more constant composition of the alloy in the grain volume than in the basic material.
3. A component as claimed in claim 1, wherein the basic material and the protective coating have the following composition:
13 to 17 %-wt Co 8 to 11 %-wt Cr to 6 %-wt Al
13 to 17 %-wt Co 8 to 11 %-wt Cr to 6 %-wt Al
4.5 to 5 %-wt Ti 2 to 4 %-wt Mo 0.7 to 1.2 %-wt V
0.15 to 0.2 %-wt C
0.01 to 0.02 %-wt B
0.03 to 0.09 %-wt Zr Remainder Ni 4. A component as claimed in any one of claims 1 to 3, wherein the protective coating exhibits a grain volume that is three powers of ten finer than the basic material.
0.15 to 0.2 %-wt C
0.01 to 0.02 %-wt B
0.03 to 0.09 %-wt Zr Remainder Ni 4. A component as claimed in any one of claims 1 to 3, wherein the protective coating exhibits a grain volume that is three powers of ten finer than the basic material.
5. A component as claimed in any one of claims 1 to 3, wherein the protective coating has fewer vanadium or titanium deposits on the grain boundaries than the basic material with an equal vanadium or titanium content.
6. A component as claimed in any one of claims 1 to 3, wherein the protective coating is a plasma spray coating.
7. A process for the production of a component of a basic material based on nickel or cobalt, with a protective coating of the same chemical composition to ensure protection against oxidation, corrosion, and thermal fatigue, comprising the steps of:
a) pre-treating the surface of the component by removal of the surface of the basic material so as to improve adhesion;
b) coating the basic material by plasma spraying using plasma-spray material that is of the same chemical composition as the basic material;
c) carrying out epitactic recrystallisation by means of solution heat treatment at temperatures between 1150°C and 1250°C ; and d) carrying out after-treatment of the surface of the protective coating by mechanical consolidation to smooth and strengthen the surface and/or the diffusion coatings so as to increase resistance to oxidation.
a) pre-treating the surface of the component by removal of the surface of the basic material so as to improve adhesion;
b) coating the basic material by plasma spraying using plasma-spray material that is of the same chemical composition as the basic material;
c) carrying out epitactic recrystallisation by means of solution heat treatment at temperatures between 1150°C and 1250°C ; and d) carrying out after-treatment of the surface of the protective coating by mechanical consolidation to smooth and strengthen the surface and/or the diffusion coatings so as to increase resistance to oxidation.
8. A process as claimed in claim 7, wherein removal is effected by means of chemical etching, plasma etching, or abrasive jet processing such as shot peening.
9. A component as claimed in claim 7 or 8, wherein the surface of the protective coating is processed by a jet process to increase hardness and/or pressure-flow lapping and/or vibratory grinding.
10. A component as claimed in any one of claims 1 to 3, wherein the surface of the protective coating is subjected to after-treatment with a diffusion coating with aluminum and/or chromium.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE3907625A DE3907625C1 (en) | 1989-03-09 | 1989-03-09 | |
| DEP3907625.3 | 1989-03-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2011753A1 true CA2011753A1 (en) | 1990-09-09 |
Family
ID=6375923
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002011753A Abandoned CA2011753A1 (en) | 1989-03-09 | 1990-03-08 | Structural element with protective coating on nickel or cobalt |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0386618B1 (en) |
| JP (1) | JPH02277760A (en) |
| CA (1) | CA2011753A1 (en) |
| DE (1) | DE3907625C1 (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2950436B2 (en) * | 1990-03-15 | 1999-09-20 | 株式会社東芝 | Manufacturing method of composite material |
| US5316866A (en) * | 1991-09-09 | 1994-05-31 | General Electric Company | Strengthened protective coatings for superalloys |
| JP3571052B2 (en) * | 1995-07-25 | 2004-09-29 | シーメンス アクチエンゲゼルシヤフト | Products with metal body |
| US5881972A (en) * | 1997-03-05 | 1999-03-16 | United Technologies Corporation | Electroformed sheath and airfoiled component construction |
| EP1162284A1 (en) | 2000-06-05 | 2001-12-12 | Alstom (Switzerland) Ltd | Process of repairing a coated component |
| DE102004050474A1 (en) | 2004-10-16 | 2006-04-20 | Mtu Aero Engines Gmbh | Process for producing a component coated with a wear protection coating |
| DE102011087159B3 (en) * | 2011-11-25 | 2013-03-28 | Mtu Aero Engines Gmbh | Priming preparation for cold gas spraying and cold gas spraying device |
| PL3050997T3 (en) * | 2013-09-25 | 2018-12-31 | The Chugoku Electric Power Co., Inc. | Method for diffusion coating heat-resistant metal member with creep reinforcement material, and creep-strength-enhanced heat-resistant metal member |
| KR102182690B1 (en) * | 2014-11-11 | 2020-11-25 | (주) 코미코 | Internal member applying plasma treatment apparatus and method for manufacturing the same |
| KR102182699B1 (en) * | 2014-11-11 | 2020-11-25 | (주) 코미코 | Internal member applying plasma treatment apparatus and method for manufacturing the same |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4419416A (en) * | 1981-08-05 | 1983-12-06 | United Technologies Corporation | Overlay coatings for superalloys |
| US4532191A (en) * | 1982-09-22 | 1985-07-30 | Exxon Research And Engineering Co. | MCrAlY cladding layers and method for making same |
| DE3246507C2 (en) * | 1982-12-16 | 1987-04-09 | BBC Aktiengesellschaft Brown, Boveri & Cie., Baden, Aargau | High temperature protection layer |
| US4743514A (en) * | 1983-06-29 | 1988-05-10 | Allied-Signal Inc. | Oxidation resistant protective coating system for gas turbine components, and process for preparation of coated components |
| DE3426201A1 (en) * | 1984-07-17 | 1986-01-23 | BBC Aktiengesellschaft Brown, Boveri & Cie., Baden, Aargau | PROCESS FOR APPLYING PROTECTIVE LAYERS |
| DE3683091D1 (en) * | 1985-05-09 | 1992-02-06 | United Technologies Corp | PROTECTIVE LAYERS FOR SUPER ALLOYS, WELL ADAPTED TO THE SUBSTRATES. |
| DE3522646A1 (en) * | 1985-06-25 | 1987-01-08 | Wiederaufarbeitung Von Kernbre | MOLDED BODY FROM BAD WELDABLE MATERIAL |
-
1989
- 1989-03-09 DE DE3907625A patent/DE3907625C1/de not_active Expired - Lifetime
-
1990
- 1990-03-01 EP EP90103963A patent/EP0386618B1/en not_active Expired - Lifetime
- 1990-03-08 JP JP2059815A patent/JPH02277760A/en active Pending
- 1990-03-08 CA CA002011753A patent/CA2011753A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| DE3907625C1 (en) | 1990-02-15 |
| JPH02277760A (en) | 1990-11-14 |
| EP0386618B1 (en) | 1994-02-16 |
| EP0386618A1 (en) | 1990-09-12 |
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