JP3999491B2 - Forming method of coating layer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a corrosion-resistant and oxidation-resistant coating layer on the surface of a refractory metal member.
[0002]
[Prior art]
In recent years, fossil fuels used in gas turbines and jet engines have been increasing in the concentration of harmful components such as sulfur. This is because the consumption of fossil fuel, which is a limited resource, has progressed, and as a result, fuel with a high content of sulfur and the like has to be used.
[0003]
In addition, in gas turbines, jet engines, and the like, the inlet gas temperature tends to increase for higher efficiency. As a result, blades and nozzles of gas turbines, jet engines, etc. are susceptible to high temperature corrosion due to contact with high temperature corrosive combustion gas generated from low-quality fuel with high sulfur content. Therefore, it is desired to improve the corrosion resistance and oxidation resistance of the heat resistant metal member used in a high temperature environment.
[0004]
Conventionally, as a heat-resistant metal member that can be used as a structural material in a high temperature environment of 1500 ° C. or higher, an intermetallic compound of molybdenum or tungsten and silicon, an intermetallic compound of niobium, tantalum or iridium and aluminum, and the like have been studied. The intermetallic compound has a high melting point and is excellent in mechanical strength, corrosion resistance, oxidation resistance, etc. in a high temperature environment, but has a problem that it is extremely poor in toughness and cannot be used alone as a structural material. .
[0005]
On the other hand, it has been proposed to use a refractory metal having a high melting point as a structural material in a high temperature environment. A heat-resistant metal such as molybdenum, tungsten, niobium, tantalum, and iridium has an extremely high melting point of 2500 to 3400 ° C. and has high toughness even in a high temperature environment. However, there is a problem that all of the refractory metals are easily oxidized in a high temperature environment.
[0006]
Therefore, it has been attempted to coat the surface of the refractory metal with an intermetallic compound having excellent corrosion resistance and oxidation resistance under a high temperature environment . As a method of coating the surface of the pre-Symbol refractory metal in the intermetallic compound, pack cementation, chemical vapor deposition, slurry cementation method is a method of utilizing the diffusion phenomenon of the dipping method or the like, for example, pack cementation method Has reported that the surface of a refractory metal member made of niobium is coated with a molybdenum-silicon intermetallic compound (TA Kircher, Mater. Sci. Eng., A155 (1992), 67).
[0007]
However, in the method using the diffusion phenomenon, since the moving speed of atoms due to diffusion is extremely low, only a thin coating layer having a thickness of about several μm to several tens of μm can be obtained even if a long time treatment is performed at a high temperature. However, such a thin coating layer has a disadvantage that it is difficult to sufficiently protect the refractory metal member in a high temperature corrosive environment. Further, in the method using the diffusion phenomenon, not only the surface of the refractory metal member to be coated but also the entire refractory metal member must be heated for a long time, so that the microstructure of the refractory metal changes. As a result, the physical properties of the refractory metal itself deteriorate.
[0008]
[Problems to be solved by the invention]
The present invention eliminates such disadvantages and provides the surface of the refractory metal member with a sufficient thickness to protect the refractory metal member in a high temperature corrosive environment without deteriorating the physical properties of the refractory metal itself. It aims at providing the method of forming a corrosion-resistant oxidation-resistant coating layer.
[0009]
[Means for Solving the Problems]
In order to achieve this object, the method for forming a coating layer according to the present invention comprises disposing a coating layer forming material comprising aluminum and nickel on the surface of a heat-resistant metal member comprising nickel or a nickel alloy , and at least the coating layer forming material. by locally heating the, 1-1.5 mm in order to afford an intermetallic compound consisting of the coated layer forming material to each other, made from the intermetallic compound, to protect the heat resistant metal member under high temperature corrosive environment It is characterized in that a corrosion-resistant and oxidation-resistant coating layer having a thickness of 5 mm is formed.
[0011]
In the method of the present invention, first, the coating layer forming material is disposed on the surface of the refractory metal member, and at least the coating layer forming material is locally heated. As a result, the coating layer forming material is melted to generate an intermetallic compound between a plurality of coating layer forming materials made of different metals. By metal that is melted is solidified, the heat surface of the metal member, corrosion oxidation resistant coating layer comprising the intermetallic compound, in order to protect the heat resistant metal member under high temperature corrosive environments 1-1 To a thickness of 5 mm .
[0012]
Further, since the refractory metal member is only heated locally, deterioration of the refractory metal itself can be avoided. The coating layer can be formed in a predetermined range on the surface of the refractory metal member by continuously performing an operation of locally heating the refractory metal member and the coating layer forming material.
[0013]
The coating layer forming material can be used in at least one form selected from a rod shape, a linear shape, a ribbon shape, and a powder shape. The coating layer forming material can be continuously supplied to the heated portion to form a desired thickness corrosion-resistant and oxidation-resistant coating layer.
[0014]
The heat-resistant metal member and the coating layer forming material can be heated by arc discharge, laser irradiation, or the like, but is preferably performed by arc discharge in order to heat more locally.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is an explanatory cross-sectional view showing the method of this embodiment, FIG. 2 is an explanatory cross-sectional view showing the structure of a corrosion-resistant and oxidation-resistant coating layer obtained according to one aspect of this embodiment, and FIG. FIG. 4 is a graph showing the Vickers hardness of the corrosion-resistant and oxidation-resistant coating layer shown in FIG .
[0021]
In the method of this embodiment, first, as shown in FIG. 1 , a plurality of coating layer forming materials 2 a and 2 b are arranged on the surface of the refractory metal member 1. The coating layer forming materials 2a and 2b are made of different metals and can be melted to form an intermetallic compound. The coating layer forming materials 2a and 2b are used in the form of, for example, a rod, a line, a ribbon, or a powder.
[0022]
Next, by generating an arc discharge D between the carbon electrode 4 connected to the refractory metal member 1 via the power supply device 3 and the refractory metal member 1, the coating layer forming materials 2a and 2b are locally produced. Heat. By doing in this way, the coating layer forming materials 2a and 2b are melted, and an intermetallic compound made of a metal constituting the coating layer forming materials 2a and 2b is generated. Moreover, the surface of the heat-resistant metal member 1 is locally melted by the heat of fusion of the metal compound. And the corrosion-resistant oxidation-resistant coating layer 5 which consists of the said intermetallic compound is formed on the said heat-resistant metal member 1 by solidifying the metal fuse | melted as mentioned above.
[0026]
In the method shown in FIG. 1, the corrosion-resistant and oxidation-resistant coating layer 5 can be formed in a predetermined range on the surface of the refractory metal member 1 by continuously performing the local heating on the refractory metal member 1.
[0027]
In the method of the present embodiment, the refractory metal member 1, it can be used nickel or nickel alloy, the coating layer-forming material 2, Ru can be used aluminum or nickel. When aluminum and nickel are used as the coating layer forming material 2 for the heat-resistant metal member 1 made of nickel or a nickel alloy, nickel aluminide and trinickel aluminide are generated as the intermetallic compound.
[0034]
A nickel or surface of the refractory metal member 1 made of nickel alloy, if to produce nickel aluminide and tri nickel aluminide as the intermetallic compound, and a base metal phase of refractory metal member 1, the intermetallic compound phase of nickel aluminide The three phases can coexist by sharing the intermetallic compound phase of trinickel aluminide as an intermediate layer.
[0037]
Next, examples of the present invention will be described.
[0038]
[Example 1]
In this embodiment, a nickel-base superalloy (trade name, Inconel # 600) base material having a diameter of 15 mm and a thickness of 5 mm is used as the refractory metal member 1, and the surface of the refractory metal member 1 as shown in FIG. The ribbon-shaped nickel and the ribbon-shaped aluminum as the coating layer forming material 2 were arranged in an equimolar ratio. Then, by generating an arc discharge D between the tungsten electrode 4 and the refractory metal member 1, the nickel-base superalloy substrate, ribbon-like nickel, and ribbon-like aluminum were locally heated.
[0039]
According to the heating, first, ribbon-like nickel and ribbon-like aluminum were melted, and then the nickel-base superalloy substrate was melted by the heat of fusion of the produced nickel aluminide. And the corrosion resistance oxidation-resistant coating layer 5 was formed by joining the said nickel aluminide to the base-material surface at the time of solidification of the metal fuse | melted as mentioned above. The heating was performed for 2 seconds so that the entire surface of the nickel-base superalloy substrate was covered with the corrosion-resistant and oxidation-resistant coating layer 5.
[0040]
As a result, as shown in FIG. 2, a corrosion-resistant and oxidation-resistant coating layer 5 having a thickness of about 1.5 mm was formed on the surface of the heat-resistant metal member 1 made of the nickel-base superalloy substrate . The corrosion-resistant and oxidation-resistant coating layer 5 includes a surface layer 6a made of nickel aluminide (NiAl3) which is an intermetallic compound of nickel and aluminum, and nickel aluminide and trinickel aluminide (Ni3Al) which are intermetallic compounds of nickel and aluminum. The surface layer 6a is firmly bonded to the surface of the refractory metal member 1 through the intermediate layer 6b.
[0041]
Next, the chemical composition of the heat-resistant metal member 1 coated with the corrosion-resistant and oxidation-resistant coating layer 5 was measured with an X-ray microanalyzer. The results are shown in FIG. 3 as the relationship between the depth from the surface of the heat-resistant metal member 1 coated with the corrosion-resistant and oxidation-resistant coating layer 5 and the atomic concentration.
[0042]
From FIG. 3, the nickel concentration is about 60% and the aluminum concentration is about 40% from the surface of the refractory metal member 1 coated with the corrosion-resistant oxidation-resistant coating layer 5 to a depth of about 1 mm. It is made of nickel aluminide rich in. The composition is considered to be a result of melting the nickel-based superalloy substrate by nickel aluminide formed by melting ribbon-like nickel and ribbon-like aluminum in an equimolar ratio, and is not a stoichiometric composition. It is a value within the solubility limit of aluminide. Further, in the region having a depth of about 1 to 1.5 mm from the surface, the nickel concentration fluctuates between 60 to 70% and the aluminum concentration varies between 10 to 30%. It shows that aluminide and trinickel aluminide coexist. In a region deeper than about 1.5 mm from the surface, the aluminum concentration is substantially 0, while the nickel concentration is about 70%, which is the concentration in the nickel-based superalloy substrate. It shows that the physical properties of the material itself have not changed.
[0043]
Next, the Vickers hardness of the heat-resistant metal member 1 coated with the corrosion-resistant and oxidation-resistant coating layer 5 was measured. The results are shown in FIG. 4 as the relationship between the depth from the surface of the heat-resistant metal member 1 covered with the corrosion-resistant and oxidation-resistant coating layer 5 and the Vickers hardness.
[0044]
From FIG. 4, in the region corresponding to the surface layer 6a and the intermediate layer 6b from the surface to a depth of about 1.5 mm, the Vickers hardness increases, whereas the refractory metal member (nickel It is clear that the Vickers hardness is low in the region corresponding to the base superalloy base material 1 having a depth of 1.5 mm or more, and the nickel base superalloy base material retains the original toughness.
[0045]
Further, the melting point of the nickel aluminide is 1638 ° C., and the melting point of the trinickel aluminide is 1395 ° C., and it is expected that the heat-resistant metal member 1 is protected by the corrosion-resistant and oxidation-resistant coating layer 5 in a high temperature corrosion environment.
[0046]
Therefore, according to the method of the present embodiment, the nickel-base superalloy substrate is protected on the surface of the refractory metal member 1 in a high-temperature corrosive environment without deteriorating the physical properties of the nickel-base superalloy substrate itself. It is apparent that the corrosion-resistant and oxidation-resistant coating layer 5 having a sufficient thickness can be formed.
[Brief description of the drawings]
FIG. 1 is an explanatory sectional view showing a method of the present invention.
FIG. 2 is an explanatory cross-sectional view showing the structure of a corrosion-resistant and oxidation-resistant coating layer obtained according to an embodiment of the present invention.
3 is a graph showing the composition of the corrosion-resistant and oxidation-resistant coating layer shown in FIG.
4 is a graph showing the Vickers hardness of the corrosion-resistant and oxidation-resistant coating layer shown in FIG .
[ Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Heat-resistant metal member, 2a, 2b ... Coating layer forming material, 5 ... Corrosion-resistant oxidation-resistant coating layer.

Claims (3)

A metal composed of the coating layer forming materials by disposing a coating layer forming material composed of aluminum and nickel on the surface of the heat-resistant metal member composed of nickel or a nickel alloy, and locally heating at least the coating layer forming material. An intermetallic compound is formed, the intermetallic compound is formed, and a corrosion-resistant and oxidation-resistant coating layer having a thickness of 1 to 1.5 mm is formed to protect the heat-resistant metal member in a high-temperature corrosive environment. A method for forming a coating layer.   The method for forming a coating layer according to claim 1, wherein the coating layer forming material is used in at least one form selected from a rod shape, a linear shape, a ribbon shape, and a powder shape.   The method for forming a coating layer according to claim 1, wherein the heating is performed by arc discharge.

Images