Metal carbide coated material

Abstract

To provide a metal carbide coated material capable of increasing the number of repeated uses.SOLUTION: A metal carbide coated material comprises: a carbon base material 14 with carbon as a main component; and a metal carbide coating film that coats at least a part of the carbon base material 14 and has a metal carbide as a main component. Between 0% to 80% of a film depth in a thickness direction of the metal carbide coating film, a carbon concentration in the metal carbide coating film increases as the film depth increases.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a carbide-coated material including a carbon-based material mainly composed of carbon and a carbide coating film mainly composed of a carbide metal that coats at least a part of the carbon-based material.

Background Art

[0002] Carbides such as tantalum carbide, niobium carbide, zirconium carbide, hafnium carbide, and tungsten carbide have high melting points and are excellent in chemical stability, strength, toughness, and corrosion resistance. Therefore, by coating a carbon-based material with a carbide, properties such as heat resistance, chemical stability, strength, toughness, and corrosion resistance of the carbon-based material can be improved. A carbide-coated material in which a carbide film is coated on the surface of a carbon-based material, particularly a tantalum carbide-coated material, is used as a member of a semiconductor single crystal manufacturing apparatus such as Si (silicon), SiC (silicon carbide), GaN (gallium nitride), and AlN (aluminum nitride). As a method for manufacturing a bulk single crystal of SiC, the sublimation recrystallization method is widely known. In the sublimation recrystallization method, a SiC raw material is filled inside a crucible, and a SiC seed crystal is placed on top of it. Also, a guide member for guiding a sublimation gas to a single crystal is installed around the SiC seed crystal. The sublimation gas generated by heating the SiC raw material rises along the inner wall of the guide member, and a SiC single crystal grows on the SiC seed crystal. In addition, a SiC single crystal substrate used for semiconductor devices and the like is manufactured by epitaxially growing a SiC single crystal on a SiC substrate composed of a bulk single crystal. Known methods for epitaxially growing a SiC single crystal include the liquid phase epitaxy (LPE) method, the vapor phase epitaxy (VPE) method, and the chemical vapor deposition (CVD) method. The method for epitaxially growing a SiC single crystal is usually the CVD method. In the epitaxial growth method by the CVD method, a SiC substrate is placed on a susceptor in the apparatus, and a raw material gas is supplied at a high temperature of 1500 °C or higher to grow a SiC single crystal. In such a method for manufacturing a SiC single crystal, in order to obtain a higher-quality crystal, Patent Document 1 discloses a method using a crucible in which the inner surface of a graphite substrate is coated with tantalum carbide. Further, Patent Document 2 discloses a method using a guide member in which the inner wall is coated with tantalum carbide.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is known that a SiC single crystal grown by using a metal carbide coating material as a crucible or a guide member has a significantly improved crystal growth yield compared to the case where crystal growth is performed using an uncoated carbon material. From the perspective of crystal manufacturing cost, it is desirable that the metal carbide coating material be used repeatedly a large number of times. Therefore, an object of the present invention is to provide a metal carbide coating material that can increase the number of repeated uses.

Means for Solving the Problems

[0005] As a result of intensive studies, the present inventors have found that by focusing on the carbon concentration in the metal carbide coating film, the number of repeated uses of the metal carbide coating material can be increased, and thus the present invention has been completed. The gist of the present invention is as follows. [1] A metal carbide coating material including a carbon substrate mainly composed of carbon and a metal carbide coating film mainly composed of a metal carbide that coats at least a part of the carbon substrate, Regarding the thickness direction of the metal carbide coating film, a metal carbide coating material characterized in that the carbon concentration in the metal carbide coating film increases as the film depth represented by the following formula increases between 0% and 80%.

Number

Number

Effect of the Invention

[0006] According to the present invention, a metal carbide coating material capable of increasing the number of repeated uses can be provided.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0008] The carbon metal coating material of the present invention includes a carbon base material mainly composed of carbon and a carbon metal coating film mainly composed of a carbon metal that coats at least a part of the carbon base material. Here, "mainly composed of carbon" means that carbon occupies 50% by mass or more of all substances constituting the carbon base material, and "mainly composed of a carbon metal" means that the carbon metal occupies 50% by mass or more of all substances constituting the carbon metal coating film. The carbon metal coating film may be a coating film of a high melting point carbide such as tantalum carbide, niobium carbide, zirconium carbide, hafnium carbide, tungsten carbide, or a composite coating film in which two or more of these high melting point carbides are combined. The carbon metal in the carbon metal coating film is preferably a carbide of at least one metal element among tantalum and niobium.

[0009] Hereinafter, the carbon metal coating material of the present invention will be described by taking a tantalum carbide coating material as an example.

[0010] [Regarding the tantalum carbide coating material] Hereinafter, a tantalum carbide coating material according to an embodiment of the present invention will be described with reference to FIG. 1. A tantalum carbide coating material according to an embodiment of the present invention includes a carbon base material 14 mainly composed of carbon and a tantalum carbide coating film mainly composed of tantalum carbide that coats the carbon base material 14. Note that the tantalum carbide coating film may coat a part of the carbon base material 14 or may coat all of the carbon base material 14.

[0011] As the carbon base material 14, for example, a base material of a carbon material such as isotropic graphite, extruded graphite, pyrolytic graphite, or a carbon fiber reinforced carbon composite material (C / C composite) can be used. The shape and properties of the carbon base material 14 are not particularly limited. The carbon base material 14 can be processed into an arbitrary shape according to the application and used.

[0012] The tantalum carbide coating material according to an embodiment of the present invention can be produced by forming a tantalum carbide coating film on the surface of a carbon substrate 14. The tantalum carbide coating film can be formed on the surface of the carbon substrate 14 by methods such as, for example, chemical vapor deposition (CVD) method, sintering method, carbonization method, etc. Among these, the CVD method is preferable as a method for forming the tantalum carbide coating film because it can form a uniform and dense film.

[0013] Furthermore, the CVD method includes a thermal CVD method, a photo CVD method, a plasma CVD method, etc., and for example, the thermal CVD method can be used for forming the tantalum carbide coating film. The thermal CVD method has advantages such as a relatively simple apparatus configuration and no damage by plasma. The formation of the tantalum carbide coating film by the thermal CVD method can be carried out using, for example, an external heating type reduced pressure CVD apparatus 10 as shown in FIG. 1. In the external heating type reduced pressure CVD apparatus 10, in a reaction chamber 12 equipped with a heater 13, a raw material supply section 16, an exhaust section 17, etc., the carbon substrate 14 is supported by a support means 15.

[0014] The manufacturing method of the tantalum carbide coating material according to an embodiment of the present invention will be described with reference to FIG. 1. First, the carbon substrate 14 is placed in the reaction chamber 12 of the external heating type reduced pressure CVD apparatus 10. The carbon substrate 14 is supported by a support means 15 having a support portion with a pointed tip.

[0015] Next, the reaction chamber 12 is heated. For example, the reaction chamber 12 is heated under conditions of an atmospheric pressure of 10 to 1000 Pa and a temperature of 800 to 2200°C.

[0016] Next, a tantalum carbide coating film is formed on the surface of the carbon base material 14. As raw material gases, a gas of a compound containing carbon atoms such as methane (CH4), hydrogen (H2), and a tantalum halide gas such as tantalum pentachloride (TaCl5) are supplied from the raw material supply unit 16 to the reaction chamber 12. The tantalum halide gas can be generated, for example, by a method of heating and vaporizing tantalum halide, a method of reacting tantalum metal with a halogen gas, or the like. Subsequently, the raw material gas supplied from the raw material supply unit 56 is subjected to a thermal CVD reaction under high-temperature and reduced pressure of 800 to 2200 °C and 1 to 1000 Pa to form a tantalum carbide coating film on the carbon base material 14.

[0017] [Method for Controlling Carbon Content in Tantalum Carbide Coating Film] The produced tantalum carbide-coated material is annealed at a heating temperature of 2000 °C or higher and a heating time of 50 hours or longer. At this time, it is preferable to set the inside of the reaction furnace to a reducing gas atmosphere. As the reducing gas, a compound that does not become an impurity in the growth of SiC single crystal is preferable. Specifically, hydrogen gas and SiCx gas are preferable. When annealing is performed with such a gas, decarburization occurs from the surface of the tantalum carbide coating film. On the other hand, due to long-time annealing, carbon atoms in the carbon base material diffuse through the tantalum carbide coating film. Due to the above two effects, a tantalum carbide coating film having a carbon concentration gradient is formed from the film surface of the tantalum carbide coating film toward the carbon base material. As a result, in the thickness direction of the tantalum carbide coating film, when the film depth represented by the following formula is between 0% and 80%, the carbon concentration in the tantalum carbide coating film increases as the film depth increases. [Equation] Also, in the thickness direction of the tantalum carbide coating film, even when the film depth represented by the above formula is between 20% and 80%, the carbon concentration in the tantalum carbide coating film increases as the film depth increases. Note that the film depth is set between 20% and 80% in order to prevent carbon in the impurities adhering to the surface of the tantalum carbide coating film from being measured as carbon in the tantalum carbide coating film in the measurement of the carbon concentration in the tantalum carbide coating film. Note that the distance from the film surface of the tantalum carbide coating film to the carbon substrate is specifically the distance between the film surface of the tantalum carbide coating film and the interface between the tantalum carbide coating film and the carbon substrate in the thickness direction of the tantalum carbide coating film.

[0018] The tantalum carbide coating material of one embodiment of the present invention described above is an example of the carbide coating material of the present invention, and the carbide coating material of the present invention is not limited to the tantalum carbide coating material of one embodiment of the present invention. Further, the carbide metal of the carbide metal coating film of the present invention is not limited to tantalum carbide. Examples of the carbide metal of the carbide metal coating film of the present invention include tantalum carbide, niobium carbide, zirconia carbide, hafnium carbide, tungsten carbide, and the like. These carbides can be used alone or in combination of two or more. Among these carbide metals, tantalum carbide and niobium carbide are preferable, and tantalum carbide is more preferable because they have the highest melting point and excellent chemical stability, strength, and corrosion resistance.

[0019] [Regarding film thickness] The thickness of the carbide metal coating film is not particularly limited. However, if the carbide metal coating film is too thin, the gas generated from the carbon substrate may pass through the carbide metal coating film and adversely affect the semiconductor single crystal. On the other hand, if the carbide metal coating film is too thick, the film formation time will be prolonged, and the film formation cost may increase. Considering these factors together, the thickness of the carbide metal coating film is preferably 10 μm or more and 100 μm or less, and more preferably 20 μm or more and 50 μm or less. Note that the thickness of the carbide metal coating film here is a value measured based on the cross-sectional observation of the carbide metal coating film by a scanning electron microscope (SEM).

[0020] [Regarding carbon concentration in the film and number of repeated uses] The carbide coating material of the present invention can increase the number of repeated uses of the carbide coating material by increasing the carbon concentration in the carbide coating film as the film depth increases between 0% and 80% or between 20% and 80%. The following explanation takes a tantalum carbide coating material as an example to discuss the mechanism by which the metal carbide coating material of the present invention can increase the number of repeated uses, but this discussion does not limit the present invention. Generally, tantalum carbide has high hardness and is prone to cracking. When a tantalum carbide coating material with cracks in the tantalum carbide coating film is exposed to a high-temperature corrosive environment, the carbon substrate is corroded through the cracks in the tantalum carbide coating film, and the original tantalum carbide coating film at the corroded part peels off. Once the tantalum carbide film peels off, it becomes impossible to use it repeatedly. Therefore, it is preferable that there are no cracks in the tantalum carbide coating film. On the other hand, even if the thermal expansion coefficient of the tantalum carbide coating film and that of the carbon material are matched, cracks can occur in the tantalum carbide coating film due to differences in the shape of the carbon substrate or local thermal expansion coefficients. Therefore, even in a tantalum carbide coating material with a completely matched thermal expansion coefficient, there is a limit to the number of times it can be repeatedly used.

[0021] In contrast, the tantalum carbide coating film in which the carbon concentration of the above-mentioned tantalum carbide coating film increases from the film surface toward the carbon substrate is considered to have a surface close to ductile metal tantalum and closer to tantalum carbide toward the carbon substrate. Also, in the tantalum carbide coating film of the tantalum carbide coating material according to an embodiment of the present invention, since the metal tantalum layer and the tantalum carbide layer are not separated by an interface, the generation of cracks in the vicinity of the surface is suppressed, and it is considered that the entire film can exhibit corrosion resistance equivalent to that of a tantalum carbide ratio peritoneal film where the whole film is tantalum carbide.

[0022] [Explanation of GDMS analysis] By glow discharge mass spectrometry (GDMS), the contents (mass basis) of Ta, Nb, Hf, Zr, W, C, O, Cl, Fe, Al, Ca, and S in the metal carbide coating material can be measured according to the following measurement conditions. As an apparatus used for glow discharge mass spectrometry, for example, a glow discharge mass spectrometer (manufactured by VG Elemental, trade name "VG9000") can be used. (Measurement conditions) ·Discharge Gas: Ar(7N) ·Insulator: Ceramic ·Secondary Electrode: In Orifice ·Cell: Flat Cell Assembly ·Nomakization: 1kV, 1.6mA ·Ion Current: Ta ~1.2×E-11 A ·Detectors: Faraday cup: 160msec ·Daly - multiplier: 500msec

[0023] Note that the film depth of 0% means the initial sputtering position in GDMS analysis, and the film depth of 100% means the point where the mass ratio of the main component metal element in the metal carbide coating to the carbon content in the metal carbide coating becomes 1 in GDMS analysis. Also, when the carbon concentration increases, it means that in the analysis in the film depth direction, the sputtering position (number of times) up to 80% of the depth and the elemental analysis values are approximated by a straight line using the least squares method, and the value of this slope has a positive value. For example, in an analysis having at least 10 or more sputtering points until the depth reaches 100%, it means that the slope obtained by the least squares method for the elemental analysis values from the film depth of 0% to 80% has a positive value.

[0024] The slope of the carbon concentration from the film depth of 0% to 80% obtained by the least squares method is preferably 100 - 20000 mass ppm / μm, more preferably 500 - 15000 mass ppm / μm, and still more preferably 700 - 9000 mass ppm / μm. Also, the slope of the carbon concentration from the film depth of 20% to 80% obtained by the least squares method is preferably 100 - 20000 mass ppm / μm, more preferably 500 - 15000 mass ppm / μm, and still more preferably 700 - 9000 mass ppm / μm.

Examples

[0025] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

[0026] The tantalum carbide coating materials of Examples 1 to 10 and Comparative Example 1 were produced as follows.

[0027] (Example 1) First, isotropic graphite was processed into a bottomed cylindrical shape (crucible 21) and a truncated conical cylindrical shape (guide member 22) as shown in FIG. 2, and these were used as the carbon base material 14. The arithmetic mean roughness Ra of the surface of the carbon base material 14 was 6.0 μm, and the thermal expansion coefficient of the carbon base material 14 was 7.0×10 -6 / °C. For the measurement of the thermal expansion coefficient of the carbon base material 14, a thermomechanical analyzer (TMA7300) of Hitachi High-Technologies Corporation was used, and the value of the thermal expansion coefficient in the temperature range from 200°C to 1200°C was taken as the thermal expansion coefficient of the carbon base material 14.

[0028] Next, two sets of the carbon base material 14 were placed in the reaction chamber 12 of the external heating type reduced pressure CVD apparatus 10 shown in FIG. 1. The carbon base material 14 was supported by a support means 15 having three support portions with pointed tips. The tip of the support portion is in contact with the outer surface of the carbon base material 14 in the case of the truncated conical cylindrical carbon base material 14, the outer surface of the carbon base material 14 in the case of the bottomed cylindrical carbon base material 14, the lower surface of the carbon base material 14 in the case of the disk-shaped carbon base material 14, and the outer side surface outside the carbon base material 14 in the case of the cylindrical carbon base material 14. Although only the bottomed cylindrical shape (crucible) is arranged as the carbon base material 14 in the reaction chamber 12 of the external heating type reduced pressure CVD apparatus 10 shown in FIG. 1, actually, two sets of a combination of a bottomed cylindrical shape (crucible) and a truncated conical cylindrical shape (guide member) were arranged as the carbon base material 14.

[0029] Subsequently, from the raw material supply unit 16, 0.25 SLM of methane (CH4) gas, 1.0 SLM of argon (Ar) gas as a carrier gas, 0.125 SLM of hydrogen (H2) gas, and 0.25 SLM of tantalum pentachloride (TaCl5) gas heated to 220°C and vaporized were supplied, and reacted at a pressure of 100 Pa and a temperature of 1250°C in the reaction chamber 12 to form a tantalum carbide coating film on the entire surface of the carbon base material 14.

[0030] The carbon substrate 14 coated with a tantalum carbide coating film was taken out from the reaction chamber 12, and a crucible and a guide member made of a tantalum carbide-coated carbon material were completed. The taken-out carbon substrate 14 was put back into the reaction chamber 12, and the carbon substrate 14 was heated to 2000 °C. Then, hydrogen (H2) gas was introduced at 0.125 SLM, and while maintaining the internal pressure of the reaction chamber 12 at 5000 Pa abs, it was heated for 50 hours to perform an annealing process, and two sets of samples (crucible and guide member) were prepared.

[0031] Regarding the two sets of samples prepared, one of the samples (crucible and guide member) was destroyed, and the film thickness was calculated from the cross-sectional observation of the tantalum carbide coating film by a scanning electron microscope (SEM). Furthermore, the carbon concentration in the tantalum carbide coating film was evaluated by glow discharge mass spectrometry (GDMS). The results are shown in FIG. 4. Separately, a flaw detector was sprayed on the sample to visualize the cracks generated in the tantalum carbide coating film, and the presence or absence thereof was investigated.

[0032] Regarding the other sample (crucible and guide member), the crucible 21 and the guide member 22 prepared in the reduced-pressure heating furnace 20 as shown in FIG. 2 were installed, and a SiC single crystal was grown by the sublimation recrystallization method. The SiC raw material 25 was placed in the crucible 21, and a 2-inch diameter SiC seed crystal 24 was installed on the upper part thereof. Argon gas was introduced into the reduced-pressure heating furnace 20 at 10 to 30 SLM, the atmospheric pressure was 500 to 1000 Pa, and the temperature was 2000 to 2500 °C. The SiC raw material 25 was sublimated to grow a 5-mm-thick SiC single crystal on the SiC seed crystal 24.

[0033] The production of SiC single crystals was repeated multiple times to check the number of times the crucible 21 and the guide member 22 were used repeatedly. As a result, peeling of the tantalum carbide coating film was confirmed after 7 uses, and it became necessary to replace them with new members. These conditions and results are shown in Table 1. Also, the results of Example 1 are shown in Figure 3. The vertical axis represents the concentration (mass ppm), and the horizontal axis represents the depth (μm). The depth was converted assuming a constant sputtering rate during analysis based on the measured value of the crater depth after analysis. Note that since there are irregularities of about several μm at the bottom of the crater after analysis, there is an error in the depth direction resolution.

[0034] Regarding the definition of "in the tantalum carbide coating film", it was defined as follows. The actually measured film thickness obtained by cross-sectional observation using SEM was taken as the film thickness. Also, the measurement point where the carbon concentration increased and the Ta concentration decreased in the GDMS analysis was defined as the interface between the carbon tantalum coating film and the carbon substrate. And the first measurement was defined as a film depth of 0%, and the measurement point at the interface between the carbon tantalum coating film and the carbon substrate was defined as a film depth of 100%.

[0035] For example, in Example 1, an increase in carbon concentration and a decrease in Ta concentration were observed in the measurement of the 25-μm portion from the GDMS analysis. Therefore, from the 0th measurement (defined as a film depth of 0%) to the 25th measurement (defined as a film depth of 100%) in this measurement were defined as "in the tantalum carbide coating film".

[0036] Furthermore, the film depth from the film surface of the tantalum carbide coating film toward the carbon substrate was set such that the outermost surface was 0% and the interface between the carbon substrate and the tantalum carbide coating film was 100%. The GDMS measurement is performed in the direction of increasing film depth, but the actual sputtering proceeds in a substantially hemispherical shape as seen from the cross-sectional direction. Therefore, the sputtering depth when a certain element is detected involves an error.

[0037] This time, since the carbon concentration in the tantalum carbide coating film was the object of investigation, the range of film depth from 0 to 80% was targeted so that the carbon concentration in the tantalum carbide coating film could be discussed reliably. Similarly, at the initial stage of GDMS measurement, impurities adhering to the outermost surface can be measured. Therefore, it was considered preferable to investigate the range of film depth from 20% to 80%.

[0038]

Table 1

[0039] (Example 2) In the annealing process, the heating temperature was set to 2100 °C. Otherwise, the same operations as in Example 1 were performed. The results are shown in Table 1.

[0040] (Example 3) In the annealing process, the heating temperature was set to 2200 °C. Otherwise, the same operations as in Example 1 were performed. The results are shown in Table 1.

[0041] (Example 4) In the annealing process, the heating temperature was set to 2300 °C. Otherwise, the same operations as in Example 1 were performed. The results are shown in Table 1.

[0042] (Example 5) In the annealing process, the heating temperature was set to 2400 °C. Otherwise, the same operations as in Example 1 were performed. The results are shown in Table 1.

[0043] (Example 6) In the annealing process, the heating temperature was set to 2500 °C. Otherwise, the same operations as in Example 1 were performed. The results are shown in Table 1.

[0044] (Example 7) In the annealing process, the heating time was set to 100 hours. Otherwise, the same operations as in Example 1 were performed. The results are shown in Table 1.

[0045] (Example 8) In the annealing process, the heating time was set to 500 hours. Otherwise, the same operations as in Example 1 were performed. The results are shown in Table 1.

[0046] (Example 9) In the annealing process, the heating time was 1000 hours. Otherwise, the same operations as in Example 1 were performed. The results are shown in Table 1.

[0047] (Example 10) In the annealing process, instead of hydrogen gas, SiCx gas (SiC, Si2C, SiC2) generated when sublimating SiC powder was used. Otherwise, the same operations as in Example 1 were performed. The results are shown in Table 1.

[0048] (Example 11) Niobium pentachloride (NbCl5) was used instead of tantalum pentachloride (TaCl5). Otherwise, the same operations as in Example 1 were performed. The results are shown in Table 1.

[0049] (Comparative Example 1) The annealing process was not carried out. Otherwise, the same operations as in Example 1 were performed. The results are shown in Table 1 and Figure 4.

[0050] Comparing the results from Example 1 to Example 10 with the result of Comparative Example 1, in Examples 1 to 10 where annealing treatment was performed, regarding the thickness direction of the tantalum carbide coating film (film thickness 25 μm), when the range from the film surface to the carbon substrate was defined as film depth 0% to 100%, in the range of film depth 0% to 80%, the carbon concentration tended to increase as the film depth increased. On the other hand, in Comparative Example 1 where annealing treatment was not performed, regarding the thickness direction of the tantalum carbide coating film (film thickness 15 μm), when the range from the film surface to the carbon substrate was defined as film depth 0% to 100%, in the range of film depth 0% to 80%, the carbon concentration did not show a tendency to increase as the film depth increased. The same results were obtained in the range of film depth 20% to 80%. Furthermore, when confirming the number of repeated uses in the production of SiC single crystals, it was found that Examples 1 to 10 had a larger number of repeated uses compared to Comparative Example 1. From the above results, Examples 1 to 10, which had an increasing gradient in the carbon concentration in the film, had a larger number of possible repeated uses compared to Comparative Example 1 without a gradient, and were suitable for cost reduction.

Explanation of Symbols

[0051] 10 External-heat type vacuum CVD apparatus 11 Top chamber 12 Reaction chamber 13 Heater 14 Carbon substrate 15 Support means 16 Raw material supply section 17 Exhaust section 20 SiC single crystal growth apparatus 21 Crucible 22 Guide member 23 Upper lid 24 SiC seed crystal 25 SiC raw material

Claims

1. A metal carbide coating material comprising a carbon base material mainly composed of carbon and a metal carbide coating film mainly composed of a metal carbide that coats at least a part of the carbon base material, with respect to the thickness direction of the metal carbide coating film, when the film depth represented by the following formula is between 0% and 80%, the carbon concentration in the metal carbide coating film increases as the film depth increases. A metal carbide coating material characterized by this. 【Equation 1】

2. A metal carbide coating material comprising a carbon base material mainly composed of carbon and a metal carbide coating film mainly composed of a metal carbide that coats at least a part of the carbon base material, with respect to the thickness direction of the metal carbide coating film, when the film depth represented by the following formula is between 20% and 80%, the carbon concentration in the metal carbide coating film increases as the film depth increases. A metal carbide coating material characterized by this. 【Equation 2】

3. The metal carbide coating material according to claim 1 or 2, wherein the metal carbide is a carbide of at least one metal element among tantalum and niobium.

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