Zirconia-based composite oxide

Abstract

To provide a zirconia-based composite oxide capable of obtaining a thermal-sprayed coating excellent in thermal stability, while having a thermal expansion coefficient comparable to that of conventional products, a coating strength comparable to or higher than that of conventional products, and a thermal conductivity comparable to or lower than that of conventional products.SOLUTION: A zirconia-based composite oxide includes zirconia and a stabilizer. The stabilizer includes yttrium oxide and another stabilizer. The other stabilizer is gadolinium oxide or scandium oxide. The content of yttrium oxide is 3.66 mol% or more and 4.57 mol% or less. When gadolinium oxide is contained as the other stabilizer, the content of gadolinium oxide is 0.18 mol% or more and 0.45 mol% or less. When scandium oxide is contained as the other stabilizer, the content of scandium oxide is 0.46 mol% or more and 1.39 mol% or less. The specific surface area is 0.2 m2 / g or more and 4.5 m2 / g or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a zirconia-based composite oxide. [Background technology]

[0002] Components such as hearth rolls used in the continuous casting process in steel production and turbine blades that make up gas turbine engines are used in high-temperature environments, so they require heat resistance and strength.

[0003] Yttria-stabilized zirconia (YSZ) is known as a thermal spray material for thermal barrier coating to provide heat resistance.

[0004] For example, Patent Document 1 discloses a thermal spray material containing particles made of 8% yttria-stabilized zirconia with an average particle size of 24 μm (Example Sample 8). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2015 / 079906 Summary of the Invention [Problem to be solved by the invention]

[0006] When yttria-stabilized zirconia (YSZ) is used as a thermal spray material, the crystalline structure of the film after thermal spraying is dominated by the tetragonal and cubic phases, and the film strength is maintained at a high level. However, due to thermal stress caused by red-hot steel, the high heat of the slab, and the combustion heat of a gas turbine, part of the tetragonal phase undergoes a phase transition to the monoclinic phase and precipitates, causing volume fluctuations and potentially damaging or peeling off the sprayed film. By increasing the amount of yttria added, the cubic phase ratio can be increased and the precipitation of the monoclinic phase due to high temperature load can be suppressed. However, increasing the amount of yttria added leads to a decrease in film strength and an increase in the thermal expansion coefficient due to the presence of the cubic phase, which can cause peeling of the sprayed film. Furthermore, the turbine blades of jet engines are coated with porous films to reduce heat conduction, but these films are susceptible to damage from external particles such as dust. In addition, although the strength of the YSZ thermal spray coating can be improved by slightly reducing the yttria content, the problem is that the coating will become destabilized due to thermal stress, which will lead to earlier maintenance times.

[0007] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a zirconia-based composite oxide that can provide a thermal sprayed coating having excellent thermal stability while having a coefficient of thermal expansion that is the same as that of conventional products, a coating strength that is the same as or greater than that of conventional products, and a thermal conductivity that is the same as or less than that of conventional products.

[0008] The present inventors have conducted extensive research to address the above-mentioned challenges. As a result, they have found that by substituting a portion of the Y2O3 in yttria-stabilized zirconia with Gd2O3 or Sc2O3, the phase transition from the tetragonal phase to the monoclinic phase is reduced, resulting in excellent thermal stability, even when exposed to thermal stresses caused by red-hot steel, the high heat of a slab, or the combustion heat of a gas turbine. They have also found that the Vickers hardness of the thermal sprayed coating surface is equivalent to or greater than that of thermal sprayed coatings obtained from conventional yttria-stabilized zirconia (e.g., 8% yttria-stabilized zirconia as disclosed in Patent Document 1). This is expected to reduce damage caused by external stress. They have also found that the thermal conductivity is equivalent to or lower than that of thermal sprayed coatings obtained from conventional yttria-stabilized zirconia. [Means for solving the problem]

[0009] The present invention provides the following: (1) A composition comprising zirconia and a stabilizer, the stabilizer includes yttrium oxide and other stabilizers; the other stabilizer is gadolinium oxide or scandium oxide; The content of the yttrium oxide is 3.66 mol% or more and 4.57 mol% or less when the total content of the zirconia and the stabilizer is 100 mol%, When gadolinium oxide is contained as the other stabilizer, the content of the gadolinium oxide is 0.18 mol% or more and 0.45 mol% or less when the total amount of the zirconia and the stabilizer is 100 mol%, When scandium oxide is contained as the other stabilizer, the content of the scandium oxide is 0.46 mol% or more and 1.39 mol% or less when the total amount of the zirconia and the stabilizer is 100 mol%, Specific surface area is 0.2m 2 / g or more 4.5m 2 / g or less.

[0010] According to the configuration (1), the content of the yttrium oxide is 3.66 mol% or more and 4.57 mol% or less, and when gadolinium oxide is included as the other stabilizer, the content of the gadolinium oxide is 0.18 mol% or more and 0.45 mol% or less, so that the phase transition from the tetragonal phase to the monoclinic phase is reduced, resulting in excellent thermal stability. The Vickers hardness of the thermal spray coating surface is also improved. This is expected to reduce damage caused by external stress. The thermal conductivity is also improved. The thermal expansion coefficient is also comparable to that of conventional products. Furthermore, when the content of yttrium oxide is 3.66 mol% or more and 4.57 mol% or less, and scandium oxide is included as the other stabilizer, the content of scandium oxide is 0.46 mol% or more and 1.39 mol% or less, thereby reducing the phase transition from the tetragonal phase to the monoclinic phase and providing excellent thermal stability. The Vickers hardness of the sprayed coating surface is also improved. This is expected to reduce damage caused by external stress. The thermal conductivity is also improved. The thermal expansion coefficient is also comparable to that of conventional products. This is also clear from the examples. Although the mechanism is not clear, it is thought that the stabilizer yttrium oxide undergoes desolubilization (destabilization) due to inherent molecular motion caused by thermal stress, i.e., the phase transition from the tetragonal phase to the monoclinic phase progresses. However, by replacing a portion of the yttrium oxide with trace amounts of gadolinium oxide or scandium oxide, the inherent molecular motion of gadolinium oxide and scandium oxide cancels out the molecular motion that causes the desolubilization of yttrium oxide, thereby reducing desolubilization (destabilization) (reducing the phase transition from the tetragonal phase to the monoclinic phase). In addition, the specific surface area is 0.2m 2 / g or more 4.5m 2 / g or less, it can be suitably used as a thermal spray material.

[0011] Furthermore, the present invention provides the following: (2) The specific surface area is 0.2 m 2 / g or more 0.3m 2 The zirconia composite oxide according to (1) above, wherein the zirconia composite oxide has a viscosity of 1000 MPa or less.

[0012] The specific surface area is 0.2 m 2 / g or more 0.3m 2 When the content is 0.01 to 0.1g, the thermal spray material can be more suitably used.

[0013] Furthermore, the present invention provides the following: (3) The zirconia-based composite oxide according to (1) or (2), wherein when gadolinium oxide is contained as the other stabilizer, the content of the gadolinium oxide is 0.18 mol % or more and 0.35 mol % or less when the total of the zirconia and the stabilizer is taken as 100 mol %.

[0014] When gadolinium oxide is included as the other stabilizer, if the content of the gadolinium oxide is 0.18 mol% or more and 0.35 mol% or less, when the total of the zirconia and the stabilizer is 100 mol%, the phase transition from tetragonal to monoclinic is further reduced. In addition, the Vickers hardness of the sprayed coating surface is improved. In addition, the thermal conductivity is also improved.

[0015] Furthermore, the present invention provides the following: (4) A zirconia-based composite oxide according to any one of (1) to (3) above, which is formed under the following film-forming conditions, and the resulting thermal sprayed film has a tetragonal phase ratio of 30% or more in all crystalline phases after heat treatment at 1450°C under atmospheric pressure for 90 hours. <Film forming conditions> Spraying method: plasma spraying in air Sprayed film thickness: 150 μm Output: 28kw Working gas: Ar, 70L / min, N2, 10L / min mixed gas

[0016] When a thermal spray coating is formed under the above conditions and the resulting coating is heat-treated at 1450°C under atmospheric pressure for 90 hours, if the tetragonal phase ratio of the total crystalline phase is 30% or more, it can be said that the phase transition from the tetragonal phase to the monoclinic phase is further reduced.

[0017] Furthermore, the present invention provides the following: (5) A zirconia-based composite oxide according to any one of (1) to (3) above, which is formed under the following film-forming conditions, and the resulting thermal sprayed film has a tetragonal phase ratio of 50% or more of all crystalline phases after being heat-treated at 1450°C under atmospheric pressure for 90 hours. <Film forming conditions> Spraying method: plasma spraying in air Sprayed film thickness: 150 μm Output: 28kw Working gas: Ar, 70L / min, N2, 10L / min mixed gas

[0018] If the thermal spray coating formed under the above conditions has a tetragonal phase ratio of 50% or more among all crystalline phases after heat treatment at 1450°C under atmospheric pressure for 90 hours, it can be said that the phase transition from the tetragonal phase to the monoclinic phase is further reduced.

[0019] Furthermore, the present invention provides the following: (6) The zirconia composite oxide according to any one of (1) to (5) above, which is formed under the following film-forming conditions, and the resulting thermal sprayed film has a Vickers hardness of 300 Hv or more and 400 Hv or less. <Film forming conditions> Spraying method: plasma spraying in air Sprayed film thickness: 150 μm Output: 28kw Working gas: Ar, 70L / min, N2, 10L / min mixed gas

[0020] When the thermal sprayed film formed under the above film forming conditions has a Vickers hardness of 300 Hv or more and 400 Hv or less, it can be said that the hardness of the surface of the thermal sprayed film is sufficiently high.

[0021] Furthermore, the present invention provides the following: (7) The zirconia composite oxide according to any one of (1) to (5) above, which is formed under the following film-forming conditions and has a Vickers hardness of 310 Hv or more and 370 Hv or less when the thermal sprayed film is formed under the following film-forming conditions: <Film forming conditions> Spraying method: plasma spraying in air Sprayed film thickness: 150 μm Output: 28kw Working gas: Ar, 70L / min, N2, 10L / min mixed gas

[0022] When a thermal sprayed film formed under the above film forming conditions has a Vickers hardness of 310 Hv or more and 370 Hv or less, it can be said that the hardness of the surface of the thermal sprayed film is high. [Effects of the Invention]

[0023] According to the present invention, it is possible to provide a zirconia-based composite oxide that can produce a thermal sprayed film having excellent thermal stability while having a thermal expansion coefficient similar to that of conventional products, a film strength similar to or greater than that of conventional products, and a thermal conductivity similar to or less than that of conventional products. DETAILED DESCRIPTION OF THE INVENTION

[0024] Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to these embodiments. In this specification, the zirconia-based composite oxide is a general one that contains 10 mass % or less of impurity metal compounds, including hafnium. In addition, in this specification, the expressions "contain" and "comprise" include the concepts of "contain," "comprise," "substantially consist," and "consist only of."

[0025] The maximum and minimum values ​​of the content of each component shown below are independently the preferred minimum and maximum values ​​of the present invention, regardless of the content of other components. Furthermore, the maximum and minimum values ​​of the various parameters (measured values, etc.) shown below are independently the preferred minimum and maximum values ​​of the present invention, regardless of the content (composition) of each component.

[0026] [Zirconia-based composite oxide] The zirconia-based composite oxide according to this embodiment is Contains zirconia and a stabilizer, the stabilizer includes yttrium oxide and other stabilizers; the other stabilizer is gadolinium oxide or scandium oxide; The content of the yttrium oxide is 3.66 mol% or more and 4.57 mol% or less when the total content of the zirconia and the stabilizer is 100 mol%, When gadolinium oxide is contained as the other stabilizer, the content of the gadolinium oxide is 0.18 mol% or more and 0.45 mol% or less when the total amount of the zirconia and the stabilizer is 100 mol%, When scandium oxide is contained as the other stabilizer, the content of the scandium oxide is 0.46 mol% or more and 1.39 mol% or less when the total amount of the zirconia and the stabilizer is 100 mol%, Specific surface area is 0.2m 2 / g or more 4.5m 2 / g or less.

[0027] The zirconia-based composite oxide according to this embodiment contains zirconia and a stabilizer. The zirconia-based composite oxide may be composed of only zirconia and a stabilizer, or may contain other components as long as the effects of the present invention are achieved (as long as the effects of the present invention are not significantly impaired).

[0028] The total content of the zirconia and the stabilizer is preferably 90.5% by mass or more, and more preferably 91.0% by mass or more, when the entire zirconia-based composite oxide is taken as 100% by mass. The total content of the zirconia and the stabilizer is, for example, 93.0 mass % or less, 92.8 mass % or less, when the entire zirconia-based composite oxide is taken as 100 mass %. The total content of the zirconia and the stabilizer is preferably 90.5% by mass or more and 93.0% by mass or less, and more preferably 91.0% by mass or more and 92.8% by mass or less, when the entire zirconia-based composite oxide is taken as 100% by mass.

[0029] The content of the zirconia is preferably 90.5% by mass or more, and more preferably 91.0% by mass or more, when the entire zirconia-based composite oxide is taken as 100% by mass. The content of the zirconia is preferably 93.0% by mass or less, and more preferably 92.8% by mass or less, when the entire zirconia-based composite oxide is taken as 100% by mass. The content of the zirconia is preferably 90.5% by mass or more and 93.0% by mass or less, and more preferably 91.0% by mass or more and 92.8% by mass or less, when the entire zirconia-based composite oxide is taken as 100% by mass.

[0030] The content of the stabilizer includes yttrium oxide and other stabilizers (gadolinium oxide or scandium oxide). The stabilizer may be composed only of yttrium oxide and other stabilizers (gadolinium oxide or scandium oxide), or may contain stabilizers other than yttrium oxide, gadolinium oxide, and scandium oxide as long as the effects of the present invention are achieved (as long as the effects of the present invention are not significantly impaired). Examples of stabilizers other than yttrium oxide, gadolinium oxide, and scandium oxide include praseodymium oxide, alkaline earth metal elements, and rare earth elements.

[0031] The content of the yttrium oxide is 3.66 mol % or more and 4.57 mol % or less when the total of the zirconia and the stabilizer is taken as 100 mol %. The content of the yttrium oxide is preferably 3.78 mol % or more, and more preferably 3.89 mol % or more, when the total of the zirconia and the stabilizer is taken as 100 mol %. The content of the yttrium oxide is preferably 4.36 mol % or less, and more preferably 4.32 mol % or less, when the total of the zirconia and the stabilizer is taken as 100 mol %. The content of the yttrium oxide is preferably 3.78 mol % or more and 4.36 mol % or less, and more preferably 3.89 mol % or more and 4.32 mol % or less, when the total of the zirconia and the stabilizer is taken as 100 mol %.

[0032] The other stabilizer is gadolinium oxide or scandium oxide.

[0033] When gadolinium oxide is contained as the other stabilizer, the content of the gadolinium oxide is 0.18 mol % or more and 0.45 mol % or less when the total of the zirconia and the stabilizer is 100 mol %. When gadolinium oxide is contained as the other stabilizer, the content of the gadolinium oxide is preferably 0.181 mol % or more, and more preferably 0.185 mol % or more, when the total of the zirconia and the stabilizer is taken as 100 mol %. When gadolinium oxide is contained as the other stabilizer, the content of the gadolinium oxide is preferably 0.44 mol % or less, and more preferably 0.35 mol % or less, when the total of the zirconia and the stabilizer is taken as 100 mol %. When gadolinium oxide is contained as the other stabilizer, the content of the gadolinium oxide is preferably 0.181 mol % or more and 0.44 mol % or less, and more preferably 0.185 mol % or more and 0.35 mol % or less, when the total of the zirconia and the stabilizer is taken as 100 mol %. Even when gadolinium oxide is contained as the other stabilizer in a range of 0.18 mol % to 0.45 mol %, scandium oxide may be further contained as long as the effects of the present invention are achieved (as long as the effects of the present invention are not significantly impaired).

[0034] When scandium oxide is contained as the other stabilizer, the content of the scandium oxide is 0.46 mol % or more and 1.39 mol % or less when the total of the zirconia and the stabilizer is taken as 100 mol %. When scandium oxide is contained as the other stabilizer, the content of the scandium oxide is preferably 0.47 mol % or more, and more preferably 0.56 mol % or more, when the total of the zirconia and the stabilizer is 100 mol %. When scandium oxide is contained as the other stabilizer, the content of the scandium oxide is preferably 1.38 mol % or less, and more preferably 0.92 mol % or less, when the total of the zirconia and the stabilizer is taken as 100 mol %. When scandium oxide is contained as the other stabilizer, the content of the scandium oxide is preferably 0.47 mol % or more and 1.38 mol % or less, and more preferably 0.56 mol % or more and 0.92 mol % or less, when the total of the zirconia and the stabilizer is taken as 100 mol %. Even when scandium oxide is contained as the other stabilizer in a range of 0.46 mol % to 1.39 mol %, gadolinium oxide may be further contained as long as the effects of the present invention are achieved (as long as the effects of the present invention are not significantly impaired).

[0035] The total content of the stabilizer is preferably 4.0 mol % or more, and more preferably 4.3 mol % or more, when the total of the zirconia and the stabilizer is taken as 100 mol %. The total content of the stabilizer is preferably 6.6 mol % or less, and more preferably 6.42 mol % or less, when the total of the zirconia and the stabilizer is taken as 100 mol %. The total content of the stabilizer is preferably 4.0 mol % or more and 6.6 mol % or less, and more preferably 4.3 mol % or more and 6.42 mol % or less, when the total of the zirconia and the stabilizer is taken as 100 mol %.

[0036] The zirconia-based composite oxide has an yttrium oxide content of 3.66 mol% or more and 4.57 mol% or less, and when gadolinium oxide is contained as the other stabilizer, the gadolinium oxide content is 0.18 mol% or more and 0.45 mol% or less, thereby reducing the phase transition from tetragonal to monoclinic, resulting in excellent thermal stability. The thermal spray coating also has a good Vickers hardness. This can be expected to reduce damage caused by external stress. The thermal conductivity is also good. The thermal expansion coefficient is also comparable to that of conventional products. Furthermore, when the content of yttrium oxide is 3.66 mol% or more and 4.57 mol% or less, and scandium oxide is included as the other stabilizer, the content of scandium oxide is 0.46 mol% or more and 1.39 mol% or less, so that the phase transition from tetragonal to monoclinic is suppressed, resulting in excellent thermal stability. The Vickers hardness of the thermal spray coating surface is also improved. This is expected to reduce damage caused by external stress. The thermal conductivity is also improved. The thermal expansion coefficient is also comparable to that of conventional products.

[0037] The specific surface area of ​​the zirconia composite oxide is 0.2 m 2 / g or more 4.5m 2 / g or less. 2 / g or more 4.5m 2 / g or less, it can be suitably used as a thermal spray material. The specific surface area is preferably 0.21 m 2 / g or more, more preferably 0.22m 2 / g or more. The specific surface area is preferably 4.0 m 2 / g or less, more preferably 2.0m 2 / g or less, more preferably 0.3m 2 / g. The specific surface area is preferably 0.21 m 2 / g or more 4.0m 2 / g or less, more preferably 0.22m 2 / g or more 2.0m 2 / g or less, more preferably 0.22m 2 / g or more 0.3m 2 / g or less.

[0038] The particle diameter D of the zirconia-based composite oxide 50 The particle diameter D is preferably 10.0 μm or more and 55.0 μm or less. 50 When the particle diameter D is 10.0 μm or more, the flowability of the thermal spray material during thermal spraying is stable, and the variation in the thermal spray film thickness can be suppressed. 50 When the particle size is 55.0 μm or less, there are few particles that do not melt during thermal spraying, and a decrease in thermal spraying efficiency can be suppressed.

[0039] The particle diameter D 50 is preferably 15.0 μm or more, more preferably 20.0 μm or more, even more preferably 23.0 μm or more, and particularly preferably 27.0 μm or more. The particle diameter D 50 is preferably 45.0 μm or less, more preferably 40.0 μm or less, even more preferably 37.0 μm or less, and particularly preferably 33.0 μm or less. The particle diameter D 50 is preferably 15.0 μm or more and 45.0 μm or less, more preferably 20.0 μm or more and 40.0 μm or less, even more preferably 23.0 μm or more and 37.0 μm or less, and particularly preferably 27.0 μm or more and 33.0 μm or less.

[0040] The particle diameter D of the zirconia-based composite oxide 10 The particle diameter D is preferably 4.5 μm or more and 33.0 μm or less. 10 When the particle diameter D is 4.5 μm or more, the flowability of the thermal spray material during thermal spraying is stable, and the variation in the thermal spray film thickness can be suppressed. 10 When the particle size is 33.0 μm or less, there are few particles that do not melt during thermal spraying, and a decrease in thermal spraying efficiency can be suppressed.

[0041] The particle diameter D 10 is preferably 11.0 μm or more, more preferably 13.0 μm or more. The particle diameter D 10 is preferably 28.0 μm or less, more preferably 25.0 μm or less. The particle diameter D 10 is preferably 11.0 μm or more and 28.0 μm or less, and more preferably 13.0 μm or more and 25.0 μm or less.

[0042] The particle diameter D of the zirconia-based composite oxide 90 The particle diameter D is preferably 25.0 μm or more and 110.0 μm or less. 90 When the particle diameter D is 25.0 μm or more, the flowability of the thermal spray material during thermal spraying is stable, and the variation in the thermal spray film thickness can be suppressed.90 When the particle diameter is 110.0 μm or less, there are few particles that do not melt during thermal spraying, and a decrease in thermal spraying efficiency can be suppressed.

[0043] The particle diameter D 90 is preferably 30.0 μm or more, more preferably 35.0 μm or more. The particle diameter D 90 is preferably 90.0 μm or less, more preferably 80.0 μm or less. The particle diameter D 90 is preferably 30.0 μm or more and 90.0 μm or less, more preferably 35.0 μm or more and 80.0 μm or less. The particle diameter D 10 , the particle diameter D 50 , the particle diameter D 90 The measurement method is the same as that described in the Examples.

[0044] The zirconia-based composite oxide is preferably formed into a film under the following film-forming conditions, and the resulting sprayed film is preferably heat-treated at 1450°C under atmospheric pressure for 90 hours, after which the tetragonal phase ratio of all crystalline phases is 30% or more. <Film forming conditions> Spraying method: plasma spraying in air Sprayed film thickness: 150 μm Output: 28kw Working gas: Ar, 70L / min, N2, 10L / min mixed gas

[0045] If the thermal spray coating formed under the above conditions has a tetragonal phase ratio of 30% or more among all crystalline phases after heat treatment at 1450°C under atmospheric pressure for 90 hours, it can be said that the phase transition from tetragonal to monoclinic has been further reduced. The tetragonal phase ratio can be controlled by adjusting the content of each stabilizer within a predetermined range. Specifically, when gadolinium oxide is included as the other stabilizer, this can be achieved by setting the content of yttrium oxide to 3.66 mol% or more and 4.57 mol% or less, and the content of gadolinium oxide to 0.18 mol% or more and 0.45 mol% or less. Furthermore, when scandium oxide is included as the other stabilizer, this can be achieved by setting the content of yttrium oxide to 3.66 mol% or more and 4.57 mol% or less, and the content of scandium oxide to 0.46 mol% or more and 1.39 mol% or less.

[0046] The thermal sprayed coating formed under the above conditions has a tetragonal phase ratio of more preferably 50% or more, and even more preferably 60% or more, of the total crystal phase after being heat-treated at 1450°C under atmospheric pressure for 90 hours. The thermal spray coating formed under the above conditions is preferably heat-treated at 1450°C under atmospheric pressure for 90 hours, and the proportion of the tetragonal phase in all crystalline phases is preferably as high as possible, for example, 70% or less, or 68% or less. The thermal spray coating formed under the above conditions has a tetragonal phase ratio of 50% or more and 70% or less, and more preferably 60% or more and 68% or less, after being heat-treated at 1450°C under atmospheric pressure for 90 hours.

[0047] The zirconia-based composite oxide has a thermal expansion coefficient of 11.0×10 -6 / ℃ or more 12.5×10 -6 / °C or less is preferable. The thermal expansion coefficient is 11.0 x 10 -6 / ℃ or more 12.5×10 -6 / °C or less, it can be said that the thermal expansion coefficient is equivalent to that of the hearth roll, turbine blade, etc. As a result, peeling of the sprayed coating due to the difference in the thermal expansion coefficient can be suppressed. The thermal expansion coefficient can be within the above numerical range, for example, by forming a film under the above film forming conditions and heat-treating the resulting sprayed film at 1450°C under atmospheric pressure for 90 hours, after which the tetragonal phase ratio of all crystalline phases is set to 30% or more. The thermal expansion coefficient is a value measured by the method described in the examples.

[0048] The coefficient of thermal expansion is preferably 11.2×10 -6 / °C or more, more preferably 11.3 × 10 -6 / ℃ or more. The coefficient of thermal expansion is preferably 12.3×10 -6 / °C or less, more preferably 12.1 × 10 -6 / ℃ or less. The coefficient of thermal expansion is preferably 11.2×10 -6 / ℃ or more 12.3×10 -6 / °C or less, more preferably 11.3 × 10 -6 / ℃ or more 12.1×10 -6 / ℃ or less.

[0049] The zirconia-based composite oxide is preferably formed into a film under the following film-forming conditions, and the resulting thermal sprayed film preferably has a Vickers hardness of 300 Hv or more and 400 Hv or less. <Film forming conditions> Spraying method: plasma spraying in air Sprayed film thickness: 150 μm Output: 28kw Working gas: Ar, 70L / min, N2, 10L / min mixed gas

[0050] When the thermal sprayed film formed under the above film forming conditions has a Vickers hardness of 300 Hv or more and 400 Hv or less, it can be said that the hardness of the surface of the thermal sprayed film is sufficiently high.

[0051] The thermal sprayed coating formed under the above conditions has a Vickers hardness of more preferably 310 Hv or more, and even more preferably 320 Hv or more. The thermal sprayed coating formed under the above conditions preferably has a high Vickers hardness, for example, 390 Hv or less, or 380 Hv or less. The Vickers hardness of the thermal sprayed film formed under the above film forming conditions is more preferably 310 Hv or more and 390 Hv or less, and even more preferably 320 Hv or more and 380 Hv or less.

[0052] The zirconia-based composite oxide preferably has a thermal conductivity of 2.50 W / m K or less at 500° C. When the thermal conductivity at 500° C. is 2.50 W / m K or less, it can be said that the thermal conduction is sufficiently suppressed. The thermal conductivity at 500°C can be controlled by adjusting the content of each stabilizer within a predetermined range. Specifically, when gadolinium oxide is included as the other stabilizer, this can be achieved by setting the content of yttrium oxide to 3.66 mol% or more and 4.57 mol% or less, and the content of gadolinium oxide to 0.18 mol% or more and 0.45 mol% or less. Furthermore, when scandium oxide is included as the other stabilizer, this can be achieved by setting the content of yttrium oxide to 3.66 mol% or more and 4.57 mol% or less, and the content of scandium oxide to 0.46 mol% or more and 1.39 mol% or less. The thermal conductivity at 500°C is a value measured by the method described in the examples.

[0053] The thermal conductivity at 500°C is more preferably 2.45 W / m·K or less, and even more preferably 2.4 W / m·K or less. The thermal conductivity at 500° C. is preferably as small as possible, for example, 1.8 W / m·K or more and 1.9 W / m·K or more. The thermal conductivity at 500°C is more preferably 1.8 W / m·K or more and 2.45 W / m·K or less, and even more preferably 1.9 W / m·K or more and 2.4 W / m·K or less.

[0054] The zirconia composite oxide preferably has a thermal conductivity of 2.9 W / m K or less at room temperature (25°C). When the thermal conductivity at room temperature is 2.9 W / m K or less, it can be said that thermal conduction is sufficiently suppressed. The thermal conductivity at room temperature can be controlled by adjusting the content of each stabilizer within a predetermined range. Specifically, when gadolinium oxide is included as the other stabilizer, this can be achieved by setting the content of the yttrium oxide to 3.66 mol% or more and 4.57 mol% or less, and the content of the gadolinium oxide to 0.18 mol% or more and 0.45 mol% or less, when the total of the zirconia and the stabilizer is 100 mol%. Furthermore, when scandium oxide is contained as the other stabilizer, this can be achieved by setting the content of the yttrium oxide to 3.66 mol% or more and 4.57 mol% or less, and the content of the scandium oxide to 0.46 mol% or more and 1.39 mol% or less, when the total of the zirconia and the stabilizer is 100 mol%. The thermal conductivity at room temperature is a value measured by the method described in the examples.

[0055] The thermal conductivity at room temperature is more preferably 2.8 W / m·K or less, and even more preferably 2.7 W / m·K or less. The smaller the thermal conductivity at room temperature, the more preferable, and is, for example, 2.3 W / m·K or more, 2.4 W / m·K or more. The thermal conductivity at room temperature is more preferably 2.3 W / m·K or more and 2.8 W / m·K or less, and even more preferably 2.4 W / m·K or more and 2.7 W / m·K or less.

[0056] [Method of manufacturing zirconia-based composite oxide] An example of a method for producing a zirconia-based composite oxide will be described below, but the method for producing a zirconia-based composite oxide of the present invention is not limited to the following example.

[0057] The zirconia composite oxide according to this embodiment can be produced by an electrofusion method or a granulation sintering method.

[0058] [Electrofusion method] The method for producing a zirconia-based composite oxide by electrofusion according to this embodiment includes the following steps: A step A of mixing yttrium oxide and gadolinium oxide or scandium oxide with zirconium oxide; A step B of heating and melting the mixture obtained in the step A to obtain an ingot; and step C of crushing the ingot obtained in step B, In the step A, zirconium oxide, yttrium oxide, and gadolinium oxide or scandium oxide are mixed to have the following contents. The content of yttrium oxide in the obtained stabilized zirconium oxide composition is 3.66 mol % or more and 4.57 mol % or less, when the total of the zirconia and the stabilizer is taken as 100 mol %. When gadolinium oxide is contained as the other stabilizer, the content of the gadolinium oxide is 0.18 mol % or more and 0.45 mol % or less when the total of the zirconia and the stabilizer is 100 mol %. When scandium oxide is contained as the other stabilizer, the content of the scandium oxide is 0.46 mol % or more and 1.39 mol % or less when the total of the zirconia and the stabilizer is taken as 100 mol %.

[0059] <Process A> In step A, zirconium oxide is mixed with yttrium oxide and gadolinium oxide or scandium oxide. Commercially available zirconium oxide, yttrium oxide, gadolinium oxide, and scandium oxide can be used. High purity products are preferred, for example, those with a purity of 99.9% or higher.

[0060] <Process B> In step B, the mixture obtained in step A is heated and melted to obtain an ingot. For example, an arc-type electric furnace can be used for the heating and melting. The heating and melting conditions are not particularly limited, but are preferably in the range of 2 kWh / kg to 4 kWh / kg in terms of power consumption rate. The application time is preferably 20 minutes to 40 minutes. The melting temperature is preferably 2700°C to 3000°C.

[0061] After melting, the melt is cooled. Although the cooling method is not particularly limited, it is preferable to cool the melt slowly in the air for 10 hours or more. This produces an ingot.

[0062] <Process C> In step C, the ingot obtained in step B is crushed. The crushing method is not particularly limited, but a jaw crusher or a roll crusher can be used. The crushing may be performed, for example, to particles of 3 mm or less, or 1 mm or less.

[0063] After pulverization, the collected powder may be heat-treated, if necessary, to remove suboxides generated during the melting process or distortion within the crystals due to supercooling. The heat-treatment conditions are not particularly limited, but may be, for example, in air at 1100°C to 1300°C for 3 to 5 hours. Thereafter, pulverization and classification may be performed, if necessary. The pulverization method is not particularly limited, but pulverization can be performed using a small vibration mill or ball mill for research and testing. The pulverization may be performed, for example, to a particle size of 100 μm or less, or 53 μm or less. The classification may be performed, for example, to a particle size of 45 μm to 10 μm. A zirconia-based composite oxide is obtained through the above steps.

[0064] The method for producing a zirconia composite oxide by electrofusion has been described above.

[0065] [Granulation sintering method] The method for producing a zirconia-based composite oxide by the granulation and sintering method according to this embodiment includes the following steps: A step A-1 of adding zirconium oxide, yttrium oxide, and gadolinium oxide or scandium oxide to ion-exchanged water, and wet-mixing and pulverizing the mixture; Step B-1: drying and granulating the slurry obtained in step A-1 using a spray dryer; and step C-1 of firing the granulated powder obtained in step B-1, In the step A-1, zirconium oxide, yttrium oxide, and gadolinium oxide or scandium oxide are mixed to have the following contents. The content of yttrium oxide in the obtained stabilized zirconium oxide composition is 3.66 mol % or more and 4.57 mol % or less, when the total of the zirconia and the stabilizer is taken as 100 mol %. When gadolinium oxide is contained as the other stabilizer, the content of the gadolinium oxide is 0.18 mol % or more and 0.45 mol % or less when the total of the zirconia and the stabilizer is 100 mol %. When scandium oxide is contained as the other stabilizer, the content of the scandium oxide is 0.46 mol % or more and 1.39 mol % or less when the total of the zirconia and the stabilizer is taken as 100 mol %.

[0066] <Process A-1> In step A-1, zirconium oxide, yttrium oxide, and gadolinium oxide or scandium oxide are added to ion-exchanged water, followed by wet mixing and pulverization. Commercially available zirconium oxide, yttrium oxide, gadolinium oxide, and scandium oxide can be used. High purity products are preferred, for example, those with a purity of 99.9% or higher. The wet mixing and pulverization methods are not particularly limited, but for example, a pot mill filled with zirconia pulverization media can be used. The ion-exchanged water may be added in such a proportion that the solids concentration of the slurry after wet pulverization falls within the range of 45% by mass to 55% by mass. As an example of the pulverization conditions, 100 kg of zirconia balls Φ5 mm, 20 kg of material, and pure water are charged into a 100L ball mill and pulverized. The pulverization time may be 10 hours or more and 20 hours or less.

[0067] <Process B-1> In step B-1, the slurry obtained in step A-1 is dried and granulated using a spray dryer. The drying and granulation conditions are not particularly limited, but for example, the slurry is fed into the spray dryer at a rate of 5 kg / h to 10 kg / h. The operating conditions may be appropriately set within the ranges of an inlet temperature of 170°C to 210°C, a disk rotation speed of 7000 rpm to 10,000 rpm, and an outlet temperature of 70°C to 110°C.

[0068] If necessary, the resulting granulated powder may be sized using a sieve, for example, a sieve with a mesh size of 250 to 100.

[0069] <Process C-1> In step C-1, the granulated powder obtained in step B-1 is fired. The firing conditions are not particularly limited, but may be in the air at 1300°C to 1500°C for 3 hours to 5 hours. In this way, a zirconia-based composite oxide is obtained.

[0070] The method for producing a zirconia-based composite oxide by the granulation and sintering method has been described above. [Example]

[0071] The present invention will be described in detail below using examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. The zirconia-based composite oxides obtained in the examples and comparative examples contain 1 to 3 mass % of hafnium as an unavoidable impurity relative to zirconium (calculated using the following formula (X)). <Expression(X)> ([Mass of hafnium] / ([Mass of zirconium]+[Mass of hafnium]))×100(%)

[0072] The maximum and minimum contents of each component shown in the following examples should be considered as the preferred minimum and maximum contents of the present invention, regardless of the contents of other components. Furthermore, the maximum and minimum values ​​of the measured values ​​shown in the following examples should be considered to be the preferred minimum and maximum values ​​of the present invention, regardless of the content (composition) of each component.

[0073] [Preparation of zirconia-based composite oxide] Example 1 Zirconium oxide (purity 99.9%, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.), yttrium oxide (purity 99.99%, manufactured by Kishida Chemical Co., Ltd.), and gadolinium oxide (purity 99.99%, manufactured by Kishida Chemical Co., Ltd.) were prepared. First, 9.2 kg of zirconium oxide, 0.75 kg of yttrium oxide, and 0.05 kg of gadolinium oxide were separated and mixed. Next, using an arc-type electric furnace, a power consumption of 2.8 kWh / kg was applied for 30 minutes, and melting was carried out at 2800°C or higher. After melting, the material was slowly cooled in the atmosphere for 10 hours or more to obtain an ingot. The obtained ingot was crushed to 3 mm or less using a jaw crusher and a roll crusher, and then powder of 1 mm or less was collected using a sieve. The collected powder was heat-treated to remove suboxides generated during the melting process and distortion within the crystals due to supercooling. The heat treatment was carried out in an electric furnace in the atmosphere at 1250°C for 4 hours. The powder was then pulverized for 1 hour using a small vibration mill for testing and research (manufactured by Chuo Kakoki Co., Ltd., device name: MB-1 model, milling conditions: zirconia balls Φ10 mm and material placed in a 2 L alumina pot). The powder was then classified using a wind classifier (manufactured by Koei Sangyo Co., Ltd., device name: Ultrafine Powder Classifier Donaserec, classification conditions: 700 rpm) and a vibration sieve (manufactured by Dalton Co., Ltd., device name: Ultrasonic Vibration Sieve RF model, classification conditions: 45 μm wire mesh pass), to obtain the zirconia-based composite oxide of Example 1.

[0074] (Examples 2 to 6, 9 to 12, Comparative Examples 1 to 10) Zirconia composite oxides according to Examples 2 to 6, 9 to 12 and Comparative Examples 1 to 10 were obtained in the same manner as in Example 1, except that the mixing ratio of zirconium oxide, yttrium oxide, and gadolinium oxide was changed so that the composition would be the ratio shown in Table 1.

[0075] Example 7 BET specific surface area is 10m 2 / g of zirconia powder (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) was prepared. To 920 g of this zirconia powder, 75 g of yttrium oxide (purity 99.99%, manufactured by Kishida Chemical Co., Ltd.) and 5 g of gadolinium oxide (purity 99.99%, manufactured by Kishida Chemical Co., Ltd.) were added, and ion-exchanged water was further added. The mixture was wet mixed and pulverized for 10 hours in a pot mill filled with zirconia pulverization media. More specifically, the pulverization conditions were as follows: 100 kg of zirconia balls (Φ5 mm), 20 kg of material, and pure water were added to a 100 L ball mill, and pulverization was carried out for 10 hours. The ion-exchanged water was added in such a proportion that the solids concentration of the slurry after wet pulverization would be 40 mass%. The resulting slurry was then dried and granulated using a spray dryer. Specifically, the slurry was fed into the spray dryer at a rate of 4 kg / hour. The operating conditions were an inlet temperature of 170°C, a disk rotation speed of 10,000 rpm, and an outlet temperature of 75°C. The resulting granulated powder was sieved using a 120-mesh sieve. The sieved granulated powder was fired at 1,400°C for 3 hours to produce the zirconia-based composite oxide of Example 7.

[0076] Example 8 A zirconia-based composite oxide according to Example 8 was obtained in the same manner as in Example 7, except that the mixing ratio of zirconium oxide, yttrium oxide, and gadolinium oxide was changed so that the composition would be the ratio shown in Table 1.

[0077] Table 1 shows the compositions of the examples and comparative examples.

[0078] [Table 1]

[0079] [Tetragonal phase (t phase) ratio (%) of ZrO2 in thermal spray coating after high temperature loading] <Making of thermal sprayed coating> The surface of an alumina setter, an SSA-T square plate 50 × 50 × 1.0 mm manufactured by Nikkato Corporation, was roughened by blasting (blasting conditions: molten alumina F60). Next, the zirconia-based composite oxides of the examples and comparative examples were sprayed onto the surface of the alumina setter in the atmosphere using a plasma spraying device to form a sprayed film with a thickness of 150 μm. The thermal spraying conditions were as follows: <Thermal spraying conditions> Plasma spraying equipment (manufactured by Bay State Surface Technologies, product name: PG-120) Output: 28kw Distance from spray gun to substrate: 100 mm

[0080] The resulting sprayed coating was subjected to heat treatment in an electric furnace at 1450° C. The heat treatment times were set to 0, 30, 60, and 90 hours. After the heat treatment, the monoclinic phase ratio (m-phase ratio), tetragonal phase ratio (t-phase ratio), and cubic phase ratio (c-phase ratio) of ZrO2 were calculated from the diffracted X-ray intensity obtained at the diffraction angle of each crystalline phase using X-ray diffraction. The angles at which each crystalline phase was analyzed are as follows. Of the calculated values, the tetragonal phase (t-phase) ratio (%) is shown in Table 2. Table 2 also shows the visual surface observation results (film peeling observation results) of the thermal sprayed film after 90 hours of heat treatment. m phase: 28.2°, 31.2° T phase: 73.1°, 74.4° c phase: 73.7° T+C phase: 30.2° <Measurement conditions> XRD equipment: ULTIMA-4, manufactured by HORIBA Measurement range: 20~80° Scan speed: 4° / min Slit width: 0.01

[0081] [Table 2]

[0082] In Comparative Examples 4-6, the tetragonal crystal ratio decreased after high-temperature loading because neither gadolinium oxide nor scandium oxide was contained. Although Comparative Examples 4-6 contained praseodymium oxide, it was confirmed that praseodymium oxide could not suppress the desolvation (destabilization) of yttrium oxide, i.e., the phase transition from the tetragonal phase to the monoclinic phase.

[0083] [Measurement of thermal expansion coefficient] 1. Wet grinding using a planetary mill 900 g of φ2 mm zirconia balls, 95 g of pure water, and 150 g of the zirconia composite oxides of the Examples and Comparative Examples were placed in a zirconia pot (volume: 500 cc) and wet-ground for 15 minutes. The removed slurry was then dried at 110°C for 10 hours or more. Next, the dried sample was collected from the tray and passed through a sieve with 106 μm openings. Then, the particle size distribution was measured using a particle size distribution analyzer (LA-950) manufactured by HORIBA. 50 Check that the particle diameter D is within the range of 1.2±0.2μm. 50 If the particle diameter D is not within the range of 1.2±0.2 μm, adjust the grinding time. 50 was adjusted to be within the range of 1.2±0.2 μm. 2.Molding Particle diameter D 50 The sample adjusted to a value within the range of 1.2±0.2μm was temporarily molded in a small uniaxial press using a mold attached to the TMA device to obtain a measurement specimen, which was then subjected to CIP at 1t / cm 2 The pressure was maintained for 2 minutes to complete the molding. The TMA is a thermomechanical analyzer that measures changes in sample dimensions while applying a constant pressure to the sample during the temperature change program, and the CIP stands for cold isostatic pressing. 3. Sintering Thereafter, the molded body was heated to 1500°C at a rate of 100°C / hour, kept at 1500°C for 3 hours, and then cooled to 1000°C at a rate of 200°C / hour. 4. Measurement The thermal expansion coefficient of the resulting sintered body was measured using a differential thermal dilatometer (TD5000SA, manufactured by Brugger AXS) under the following measurement conditions. The results are shown in Table 3. <Measurement conditions for thermal expansion coefficient> Heating rate: 250°C / hour Sintering temperature and time: 1500℃, 1 hour Cooling rate: 350℃ / hour Load: 10g Atmosphere: atmospheric pressure

[0084] [Table 3]

[0085] [Measurement of thermal conductivity] 1. Wet grinding using a planetary mill 900 g of φ2 mm zirconia balls, 95 g of pure water, and 150 g of the zirconia composite oxides of the Examples and Comparative Examples were placed in a zirconia pot (volume: 500 cc) and wet-ground for 15 minutes. The removed slurry was then dried at 110°C for 10 hours or more. Next, the dried sample was collected from the tray and passed through a sieve with 106 μm openings. Then, the particle size distribution was measured using a particle size distribution analyzer (LA-950) manufactured by HORIBA. 50 Check that the particle diameter D is within the range of 1.2±0.2μm. 50 If the particle diameter D is not within the range of 1.2±0.2 μm, adjust the grinding time. 50 was adjusted to be within the range of 1.2±0.2 μm. 2.Molding Particle diameter D 50 The sample adjusted to within the range of 1.2±0.2μm is temporarily molded into a Φ20mm×5mmh using a small uniaxial molding press, and then pressed at 1t / cm using a CIP (cold isostatic pressing) machine. 2 The final molding was completed in 2 minutes. 3. Sintering Thereafter, the molded body was heated to 1500°C at a rate of 100°C / hour, kept at 1500°C for 3 hours, and then cooled to 1000°C at a rate of 200°C / hour. Next, the obtained sintered body was cut into a piece with a diameter of 10 mm and a thickness of 2 mm to prepare pellets for measuring thermal conductivity (for the laser flash method). 4. Measurement The thermal conductivity of the obtained pellets for thermal conductivity measurement was measured using a measuring device (NETZSCH, LFA457, laser flash method). The measurement temperatures were room temperature (25°C) and 500°C. The results are shown in Table 4.

[0086] [Table 4]

[0087] [Vickers hardness measurement] 1. Creating a thermal spray coating In the same manner as in the above <Preparation of Thermal Sprayed Film>, thermal sprayed films were prepared using the zirconia composite oxides of the Examples and Comparative Examples. Next, the surface of the thermal sprayed film was mirror-polished using an automatic polishing machine ("Ecomet 250" manufactured by BUEHLER). For the mirror-polished finish, a diamond paste containing diamond abrasive grains with a particle size of 3 μm was used. 2. Measurement The polished surface of the thermal spray coating was measured using a measuring device (Mitutoyo Hardness Testing Machine) under the following measurement conditions. The results are shown in Table 5. <Vickers hardness measurement conditions> Pressure: 30N Number of measurements: 5 (The average of the 5 measurements was used as the measurement result.)

[0088] [Table 5]

[0089] [Measurement of specific surface area] The specific surface areas of the zirconia composite oxides of the examples and comparative examples were measured by the BET method using a specific surface area meter ("Macsorb" manufactured by Mountec). The results are shown in Table 6.

[0090] [Particle diameter D 10 , particle diameter D 50 , particle diameter D 90 Measurement of 0.15 g of the zirconia composite oxide of each of the Examples and Comparative Examples and 40 ml of a 0.2% aqueous solution of sodium hexametaphosphate were placed in a 50 ml beaker and dispersed for 5 minutes in a tabletop ultrasonic cleaner "W-113" (manufactured by Honda Electronics Co., Ltd.), and then the beaker was placed in a laser diffraction particle size distribution analyzer ("SALD-2300" manufactured by Shimadzu Corporation) and measured. The results are shown in Table 6.

[0091] [Table 6]

Claims

1. Contains zirconia and a stabilizer, the stabilizer includes yttrium oxide and other stabilizers; the other stabilizer is gadolinium oxide or scandium oxide; the content of the yttrium oxide is 3.66 mol % or more and 4.57 mol % or less when the total of the zirconia and the stabilizer is 100 mol %, When gadolinium oxide is contained as the other stabilizer, the content of the gadolinium oxide is 0.18 mol % or more and 0.45 mol % or less when the total of the zirconia and the stabilizer is 100 mol %, When scandium oxide is contained as the other stabilizer, the content of the scandium oxide is 0.46 mol % or more and 1.39 mol % or less when the total of the zirconia and the stabilizer is 100 mol %, Specific surface area is 0.2m ２ / g or more 4.5m ２ / g or less.

2. The specific surface area is 0.2 m ２ / g or more 0.3m ２ 2. The zirconia composite oxide according to claim 1, wherein the zirconia composite oxide has a molecular weight of 1 / g or less.

3. 3. The zirconia-based composite oxide according to claim 1, wherein when gadolinium oxide is contained as the other stabilizer, the content of the gadolinium oxide is 0.18 mol % or more and 0.35 mol % or less when the total of the zirconia and the stabilizer is taken as 100 mol %.

4. 3. The zirconia-based composite oxide according to claim 1, wherein the tetragonal phase ratio of all crystalline phases is 30% or more after the thermal sprayed coating is formed under the following conditions and the resulting coating is heat-treated at 1,450°C under atmospheric pressure for 90 hours: <Film forming conditions> Spraying method: plasma spraying in air Sprayed film thickness: 150 μm Output: 28kw Working gas: Ar, 70 L / min, N ２ , 10L / min mixed gas

5. 3. The zirconia-based composite oxide according to claim 1, wherein the tetragonal phase ratio of all crystalline phases is 50% or more after the thermal sprayed coating is formed under the following conditions and the resulting coating is heat-treated at 1,450°C under atmospheric pressure for 90 hours: <Film forming conditions> Spraying method: plasma spraying in air Sprayed film thickness: 150 μm Output: 28kw Working gas: Ar, 70 L / min, N ２ , 10L / min mixed gas

6. 3. The zirconia composite oxide according to claim 1, wherein the thermal sprayed coating formed under the following conditions has a Vickers hardness of 300 Hv or more and 400 Hv or less. <Film forming conditions> Spraying method: plasma spraying in air Sprayed film thickness: 150 μm Output: 28kw Working gas: Ar, 70 L / min, N ２ , 10L / min mixed gas

7. 3. The zirconia-based composite oxide according to claim 1, wherein the thermal sprayed coating formed under the following conditions has a Vickers hardness of 310 Hv or more and 370 Hv or less. <Film forming conditions> Spraying method: plasma spraying in air Sprayed film thickness: 150 μm Output: 28kw Working gas: Ar, 70 L / min, N ２ , 10L / min mixed gas

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