JP4234936B2 - Sodium-sulfur battery anode container, method for forming spray coating on inner surface of anode container, and method for determining quality of spray coating - Google Patents

Description

【００４０】
単位厚み１０μｍ内に存在する扁平溶射粒子数が６〜８個の範囲となる溶射条件で溶射した初期溶射皮膜の厚みが６２μｍの実施例１における陽極容器溶射皮膜の残存厚みは、５９〜６０μｍであり、厚みの減少は極めて小さい。また、単位厚み１０μｍ内に存在する扁平溶射粒子数が３〜５個の範囲となる溶射条件で溶射した初期溶射皮膜の厚みが６１μｍの実施例２における陽極容器溶射皮膜の残存厚みは、５４〜５８μｍであり、実施例１に比べ若干厚みの減少は大きいものの、充分な残存厚みである。一方、実施例１とほぼ同じ厚みに溶射し、単位厚み１０μｍ内に存在する扁平溶射粒子数が１〜２個の範囲になる溶射条件で溶射した比較例１における陽極容器溶射皮膜の残存厚みは、２８〜３５μｍであり、実施例１又は２に比べて大幅な厚み減少を生じていた。
【００４１】
【発明の効果】
以上説明したように、陽極容器内周面に形成された溶射皮膜において、溶射皮膜の厚み１０μｍ単位の断面金属組織が、少なくとも３個以上の扁平溶射粒子からなる層状組織である本発明の陽極容器を用いてナトリウム−硫黄電池を組立てれば、長期に亘り運転しても、陽極容器内周面の溶射皮膜の減少が少なく、更なる長期の運転を可能にする。又、本発明の溶射皮膜品質良否判定方法に基づいて良質と判定される本発明の溶射条件で溶射する溶射方法によれば、溶射皮膜の厚み１０μｍ単位の断面金属組織が、少なくとも３個以上の扁平溶射粒子からなる層状組織である溶射皮膜を内周面に有する陽極容器が得られる。
【図面の簡単な説明】
【図１】 本発明のナトリウム−硫黄電池用陽極容器に係り、陽極容器内周面に形成された溶射皮膜の断面金属組織を示す写真である。
【図２】 図１の断面金属組織写真を模式的に示す図である。
【図３】 本発明の陽極容器内周面に形成された溶射皮膜の断面金属組織を説明する図である。
【図４】 本発明の陽極容器内周面に溶射皮膜を形成する方法を説明する図である。
【図５】 ナトリウム−硫黄電池を示す模式的断面図である。
【図６】 従来の溶射皮膜良否判定方法で良質と判定される溶射皮膜の断面金属組織を示す写真である。
【図７】 図６の溶射皮膜断面金属組織写真の模式図である。
【符号の説明】
１…扁平溶射金属粒子、２…陽極容器円筒体、３…扁平溶射金属粒子からなる層状組織、４…溶射皮膜、５…溶射ガン、６…溶射用金属粉末供給パイプ、７…回転治具、８…未溶融粒子、９…固体電解質管、１０…陽極容器、１１…底蓋、１２…安全管、１３…ナトリウム収納容器、１４…絶縁リング、１５…陰極金具、１６…陰極蓋、１７…陽極金具、１８…プラズマジェット、１９…気泡。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an anode container for a sodium-sulfur battery having a thermal spray coating excellent in corrosion resistance and durability on its inner peripheral surface, a method for forming the high-quality thermal spray coating, and a quality determination method for the thermal spray coating.
[0002]
[Prior art]
A sodium-sulfur battery is used in a power storage system for realizing functions such as power leveling and peak cut. The structure of the sodium-sulfur battery is schematically shown in FIG. That's right.
[0003]
The battery structure at the time of manufacture is such that a bottomed cylindrical beta-alumina solid electrolyte tube 9 is glass-bonded to the inner peripheral surface of the α-alumina insulating ring 14 at the upper end outer peripheral surface, and further bonded to the upper surface of the insulating ring 14. The cathode chamber 15 partitioned by the cathode fitting 15 and the cathode lid 16 welded to the cathode fitting 15, the insulating ring 14, and the beta alumina solid electrolyte tube 9 is a bottomed cylindrical metal safety tube 12 and its safety. A sodium storage container 13 storing sodium and a small amount of sodium azide is disposed inside the tube 12, while the anode chamber is connected to an anode fitting 17 joined to the lower surface of the insulating ring 14 and the anode fitting 17. A welded anode vessel 10, further a bottom lid 11 welded to the anode vessel 10, an insulating ring 14, and a beta alumina solid electrolyte tube 9, and a car impregnated with sulfur. Nmatto is disposed, on its upper a structure that inert gas is filled, such as nitrogen.
[0004]
After assembling the cell by each member, the sodium in the sodium storage container 13 is melted in the process of raising the temperature to the battery operating temperature, and nitrogen generated by decomposition of sodium azide contained in the upper part of the sodium storage container 13 Due to the pressure of the gas, molten sodium flows into the cathode chamber from a small hole provided in the bottom of the sodium container 13 and fills the cathode chamber.
[0005]
The battery operates at a temperature of 290 ° C. to 385 ° C., and sodium conducts ions in the beta alumina solid electrolyte tube 9 as sodium ions, reacts with molten sulfur in the anode chamber, generates sodium polysulfide, and the discharge reaction proceeds. To do. The reverse reaction proceeds during charging, and the molten sodium is returned to the cathode chamber.
[0006]
In the sodium-sulfur battery having the above-described configuration, an anode container made of an aluminum alloy has a corrosion sprayed coating on its inner peripheral surface because of the problem of corrosion resistance against sodium polysulfide as an anode active material. The quality of the thermal spray coating is greatly affected by the thermal spraying conditions. Therefore, conventionally, the sprayed coating sprayed on the inner peripheral surface of the anode container is embedded in a resin, mirror-polished, the sprayed coating cross section is observed with an optical microscope, the degree of melting of the sprayed particles (melted, unmelted), the size of the pores Then, the distribution and the adhesion to the substrate were examined, and the quality of the sprayed coating was judged by measuring the bonding strength between the sprayed coating and the substrate.
[0007]
Conventionally, an anode container having a low-porosity, dense, and excellent quality sprayed coating with excellent adhesion to a substrate as shown in FIGS. 6 and 7 is used in FIG. The sodium-sulfur battery shown has been assembled and fabricated. When the battery was operated for a long time, the battery after operation was disassembled, and the sprayed coating on the inner peripheral surface of the anode container was examined and measured. As a result, it was found that the sprayed coating was thinner than expected.
[0008]
[Problems to be solved by the invention]
The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an anode container for a sodium-sulfur battery having an anticorrosion spray coating excellent in corrosion resistance and durability on the inner peripheral surface. To do. It is another object of the present invention to provide a method for spraying such an anticorrosion spray coating excellent in corrosion resistance and durability on the inner peripheral surface of the anode container and a method for determining the quality of the spray coating.
[0009]
[Means for Solving the Problems]
According to the present invention, the inner circumferential surface of sodium to form a sacrificial sprayed coating in - at the anode container sulfur battery, sectional metal structure in the thickness 10μm units of the thermal spray coating is composed of at least three or more soluble morphism particles dense An anode container for a sodium-sulfur battery characterized by having a layered structure is provided.
[0010]
In the present invention, the thickness of the sprayed coating is preferably in the range of 30 μm to 80 μm.
[0011]
Further, according to the present invention, sodium - a method of forming a thermal spray coating on the inner peripheral surface of the anode container sulfur batteries, thermal spraying metal powder is a Cr-Fe alloy powder containing more than 65% of Cr, the While the amount of O ₂ in the metal powder is 1.5% or less and the metal powder is a lump powder by pulverization with a particle diameter of 75 μm or less , the spray gun is moved up and down while rotating the cylindrical anode container. When the plasma spraying is performed in the atmosphere by moving the gas to the gas, the flow rate of the primary gas using the argon gas of the spray gun is 30 to 45 l / min, and the flow rate of the secondary gas using hydrogen is 3.5 to 5.0. l / min, flow rate of carrier gas using argon carrying metal powder is 2.5 to 3.5 l / min, spray gun output is 12 to 15 kW, spray distance is 35 to 42 mm, metal powder supply amount is 70 to 81g / min, anode capacity There is provided a method for forming a sprayed coating on the inner peripheral surface of an anode container for a sodium-sulfur battery, characterized in that spraying is performed in a range of 380 to 450 rpm and a spray gun traverse speed of 8 to 15 mm / sec. The
[0013]
In a further, according to the present invention, sodium - in quality determining method of thermal spray coating formed on the inner peripheral surface of the anode container sulfur battery, chemically corrode cutting polished thermal spray coating section, made of sprayed metal particles A quality determination method for a thermal spray coating formed on the inner peripheral surface of an anode container for a sodium-sulfur battery, wherein the quality of the thermal spray coating is determined based on the number of layered structures is provided.
[0014]
In the present invention, it is preferable to determine a case where the number of layered structures made of the sprayed metal particles is 3 or more within a thickness of 10 μm as a good quality.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, although embodiment of this invention is described, it cannot be overemphasized that this invention is not limited to the following embodiment.
[0016]
FIG. 1 is a photograph showing a cross-sectional metallographic structure of a sprayed coating that protects the inner peripheral surface of an anode container for a sodium-sulfur battery according to the present invention. FIG. 2 is a locally enlarged view schematically showing the cross-sectional metal structure shown in the photograph of FIG.
As shown in FIGS. 1 and 2, the feature of the present invention is that the metallographic structure of the sprayed coating 4 formed on the inner peripheral surface of the anode container is such that the flat sprayed particles 1 and 1 are bonded to each other in layers, and the unit thickness is within 10 μm. Further, it is a layered structure composed of at least three flat spray particles 1.
[0017]
For example, when the sprayed coating 4 having a thickness of 70 μm is formed on the inner peripheral surface of the aluminum alloy anode container cylinder 2 having an outer diameter of 95 mm and a wall thickness of 1.7 mm, as shown in FIG. The unit thickness (t) means that the layered structure 3 in the unit thickness (t) is a layered structure 3 composed of at least three flat spray particles 1. That is, the entire thickness of 70 μm is a layered structure composed of 21 or more flat spray particles 1. As the thermal spray coating 4 on the inner peripheral surface of the anode container used as a sodium-sulfur battery, a Cr—Fe alloy film containing 65% Cr is preferable. The thickness of the sprayed coating is preferably 30 to 80 μm.
[0018]
Due to this feature of the present invention, even if the sodium-sulfur battery is operated for a long period of time, the thickness of the sprayed coating 4 on the inner peripheral surface of the anode container is little decreased, and the corrosion resistance and durability are maintained. Enables long-term operation. In addition, the reliability is improved.
[0019]
The inventors of the present invention based on the new determination method of the present invention as a method for determining the quality of the thermal spray coating 4 on the inner peripheral surface of the anode container, without observing the porosity in the cross section of the spray coating with a conventional optical microscope. Thus, it is possible to form the sprayed coating 4 having excellent durability on the inner peripheral surface of the anode container.
[0020]
Disassemble the battery that has been operated for a long period of time, and chemically etch the mirror-polished section of the sprayed coating 4 remaining on the inner peripheral surface of the anode container, observe the metal structure, and pay attention to the layered structure composed of flat sprayed particles. The remaining thickness of the thermal spray coating 4 and the layered structure were investigated. As a result, the present inventors have found that there is a correlation between the residual thickness and the lamellar structure composed of the flat spray particles 1 and completed the present invention.
[0021]
A method for determining the quality of the thermal spray coating 4 formed on the inner peripheral surface of the anode container will be described. If the anode container on which the thermal spray coating 4 is formed is cut, filled with resin, then polished, and the mirror-polished cross section is chemically corroded under predetermined conditions, the metal structure composed of the sprayed metal particles can be observed. It becomes possible.
[0022]
For example, in the case of a Cr—Fe alloy film containing 65% or more of Cr, the metal structure of the sprayed coating cross section can be observed if immersed in a HCl—HNO ₃ mixed solution at room temperature for 15 minutes. If the corrosion solution and the corrosion time are appropriately set according to the type of metal of the thermal spray coating, the metal structure of the cross section of the thermal spray coating can be observed. The metallographic structure of the sprayed coating varies depending on the spraying conditions.
[0023]
Depending on the spraying conditions such as the type, particle size, particle shape, gas flow rate, spraying distance, etc. of the metal powder for thermal spraying, the metallographic structure of the thermal spray coating shall be, for example, a structure in which sprayed particles with relatively roundness are densely laminated together. You can also. Moreover, it can also be set as the structure | tissue where the thermal spray particle | grains with large flatness were densely laminated | stacked. In both cases, according to the conventional thermal spray coating quality determination method for observing the porosity of the sprayed cross section, if it is dense and has a low porosity, it is determined to be a high quality thermal spray coating. However, when the battery is operated for a long period of time, a large difference is produced between the two.
[0024]
The quality pass / fail judgment method of the present invention is a method for judging pass / fail based on the number of layered structures made of sprayed metal particles. In particular, in the thickness direction of the sprayed coating, there are 3 flat sprayed metal particles within a unit thickness of 10 μm. This is a method for determining a case where there are more than one as a good quality thermal spray coating.
[0025]
It is not clear about the mechanism that provides a high-quality sprayed coating when three or more flat sprayed metal particles are present within a unit thickness of 10 μm. When the battery is operated for a long period of time, the thickness of the sprayed coating on the inner surface of the anode container is not simply corroded under high temperature by the anode active material, but is related to the corrosion conditions peculiar to sodium-sulfur batteries. The present inventors presume that this is the case.
[0026]
That is, after assembling as a battery, the temperature rises from room temperature to the battery operating temperature, the thermal cycle of temperature rise / fall due to repeated charging / discharging over a long period of time, the temperature drop to room temperature during periodic inspection, the room temperature when restarting again Due to various thermal cycles such as temperature rise from the battery to the battery operating temperature, fine cracks are generated between the sprayed particles due to the difference in thermal expansion (thermal strain), and sodium polysulfide penetrates into the cracks. The present inventors presume that the bond between the sprayed metal particles is weakened, and the sprayed particles are sequentially peeled to reduce the thickness of the sprayed coating.
[0027]
In particular, when the battery during regular inspection is cooled to room temperature or in the process of raising the temperature to the operating temperature, the bond between the sprayed metal particles is weakened by solidification or expansion of sodium polysulfide that has entered the cracks between the sprayed metal particles. The present inventors presume that the spray particles are more easily peeled off.
[0028]
Therefore, in the case where the thermal spray coating is a metal structure composed of thermal spray metal particles having a low flatness, the bondability between the thermal spray particles is weak, and when operated as a battery for a long time, the thermal spray coating is relatively faster than the thermal spray coating of the present invention. The present inventors presume that the thickness of the film is reduced.
[0029]
Next, a method for forming a sprayed coating on the inner peripheral surface of the anode container of the present invention will be described. According to the method for forming a thermal spray coating of the present invention, it is possible to form a high-quality thermal spray coating in which three or more flat thermal spray metal particles exist within a unit thickness of 10 μm in the thickness direction of the thermal spray coating.
[0030]
The method for forming a sprayed coating of the present invention is a method in which a metal powder for thermal spraying is sufficiently melted in a plasma region so as not to be excessively oxidized, sprayed onto a substrate at a high speed, and a dense coating composed of sprayed metal particles having high flatness. This is a method for forming a sprayed coating having a low porosity layered structure.
[0031]
Specifically, as shown in FIG. 4, an anode container cylindrical body 2 made of an aluminum alloy and having an outer diameter of 95 mm and a wall thickness of 1.5 mm is rotated by a rotating jig 7 at a speed of 380 to 450 rpm. Plasma spraying is performed on the inner peripheral surface of the anode container cylindrical body 2 in the atmosphere while the thermal spray gun 5 is lowered into the cylindrical body 2 at a traverse speed of 8 to 15 mm / sec. In accordance with the thickness of the spray coating, the spray gun 5 is sprayed by reciprocating up and down in the cylindrical body 2 of the anode container.
[0032]
The metal powder for thermal spraying used is a Cr-Fe alloy powder containing 65% or more of Cr, and the amount of O ₂ in the metal powder is 1.5% or less, that is, the content of metal oxide is low, and the metal The powder is a lump powder produced by pulverization, and the powder particle diameter is sieved to 75 μm or less.
[0033]
The spray gun 5 uses argon gas as the primary gas and hydrogen as the secondary gas, and the primary gas flow rate is set to 30 to 45 l / min and the secondary gas flow rate is set to 3.5 to 5.0 l / min. A plasma jet 18 is produced by hydrogen combustion, and metal powder is blown into the plasma jet region from the supply pipe 6. At this time, the flow rate of the carrier gas using argon for carrying the metal powder is set to 2.5 to 3.5 l / min, and the supply amount of the metal powder is set to 70 to 81 g / min. Also, the spray gun output is set to 12-15 kW. Further, the distance (S) between the spray gun 5 and the anode container cylindrical body 2, that is, the spray distance (S) is set to 35 to 42 mm.
[0034]
The setting of the spraying distance (S) is a particularly important spraying condition for forming the sprayed coating of the present invention. If the spraying distance is too long, the metal powder blown into the plasma jet is sufficiently melted, but this is not preferable because oxidation of the metal powder proceeds excessively. On the other hand, if the length is shorter, the melting is insufficient and the flat sprayed metal particles 1 are not formed, or the number of flat sprayed metal particles existing within a unit thickness of 10 μm is reduced.
It is important to set the thermal spraying conditions based on the method for determining quality of the thermal spray coating of the present invention.
[0035]
【Example】
Example 1
An anode container made of an aluminum alloy and having a sprayed coating made of a Cr—Fe alloy containing 65% or more of Cr on the inner peripheral surface of an anode container cylindrical body having an outer diameter of 95 mm and a wall thickness of 1.5 mm was prepared. The thermal spraying conditions were the thermal spraying conditions under which the thermal spray coating determined to be of good quality based on the quality determination method for thermal spray coating of the present invention was obtained. Incidentally, the spraying distance was 40 mm.
[0036]
Using this anode container, a sodium-sulfur battery was assembled and operated as a battery for a predetermined period. The heat cycle conditions received by the battery during this operation period are 40 cycles, with one cycle consisting of a temperature increase from room temperature to 410 ° C. and a temperature decrease from 410 ° C. to room temperature.
The battery after operation for a predetermined period was disassembled, and the remaining thickness of the inner peripheral surface sprayed coating of the anode container was measured. The results are shown in Table 1.
[0037]
(Example 2)
An anode container was prepared under the same thermal spraying conditions as in Example 1 except that an anode container cylindrical body having the same dimensions and the same material was used and the spraying distance was set to 36 mm. And operated for the same period under the same conditions. The battery after operation was disassembled, and the remaining thickness of the inner peripheral surface spray coating of the anode container was measured. The results are shown in Table 1.
[0038]
(Comparative example)
A cylindrical structure of the same size and the same material was used, and the layered structure composed of flat spray particles existing within a unit thickness of 10 μm was prepared under the same conditions as in Example 1 or 2 except that Example 1 or 2 was different. The anode container was produced and the batteries assembled using these containers were also operated for the same period under the same conditions as in Example 1. The battery after operation was disassembled, and the remaining thickness of the inner peripheral surface spray coating of the anode container was measured. The results are shown in Table 1 as Comparative Example 1.
[0039]
[Table 1]

[0040]
The residual thickness of the anode container sprayed coating in Example 1 in which the thickness of the initial sprayed coating sprayed under the spraying condition in which the number of flat sprayed particles existing in the unit thickness of 10 μm is in the range of 6 to 8 is 59 to 60 μm. There is very little reduction in thickness. Further, the remaining thickness of the anode container sprayed coating in Example 2 in which the thickness of the initial sprayed coating sprayed under the spraying conditions in which the number of flat sprayed particles existing within the unit thickness of 10 μm is in the range of 3 to 5 is 54 to Although it is 58 μm and the thickness is slightly decreased as compared with Example 1, it is a sufficient remaining thickness. On the other hand, the remaining thickness of the sprayed coating on the anode container in Comparative Example 1 was sprayed to substantially the same thickness as in Example 1 and sprayed under spraying conditions in which the number of flat sprayed particles existing within a unit thickness of 10 μm was in the range of 1 to 2. 28 to 35 μm, which is a significant reduction in thickness compared to Example 1 or 2.
[0041]
【The invention's effect】
As described above, in the sprayed coating formed on the inner peripheral surface of the anode container, the cross-sectional metal structure having a thickness of 10 μm is a layered structure composed of at least three flat sprayed particles. When a sodium-sulfur battery is assembled using the battery, even if it is operated for a long period of time, the thermal spray coating on the inner peripheral surface of the anode container is less reduced, and further long-term operation is possible. In addition, according to the thermal spraying method for thermal spraying under the thermal spraying conditions of the present invention determined to be good based on the thermal spray coating quality determination method of the present invention, the cross-sectional metal structure having a thickness of 10 μm unit of the thermal spray coating has at least three or more. An anode container having a thermal spray coating on the inner peripheral surface, which is a layered structure made of flat spray particles, is obtained.
[Brief description of the drawings]
FIG. 1 is a photograph showing a cross-sectional metallographic structure of a sprayed coating formed on the inner peripheral surface of an anode container according to the anode container for a sodium-sulfur battery of the present invention.
2 is a diagram schematically showing a cross-sectional metallographic photograph of FIG. 1. FIG.
FIG. 3 is a view for explaining a cross-sectional metal structure of a sprayed coating formed on the inner peripheral surface of the anode container of the present invention.
FIG. 4 is a diagram illustrating a method for forming a sprayed coating on the inner peripheral surface of the anode container of the present invention.
FIG. 5 is a schematic cross-sectional view showing a sodium-sulfur battery.
FIG. 6 is a photograph showing a cross-sectional metallographic structure of a thermal spray coating that is determined to be of good quality by a conventional thermal spray coating quality determination method.
FIG. 7 is a schematic diagram of a photograph of a cross-sectional metallographic structure of a thermal spray coating in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Flat sprayed metal particle, 2 ... Cylindrical body of anode container, 3 ... Laminar structure which consists of flat sprayed metal particle, 4 ... Sprayed coating, 5 ... Spraying gun, 6 ... Metal powder supply pipe for thermal spraying, 7 ... Rotating jig, DESCRIPTION OF SYMBOLS 8 ... Unmelted particle, 9 ... Solid electrolyte tube, 10 ... Anode container, 11 ... Bottom cover, 12 ... Safety tube, 13 ... Sodium storage container, 14 ... Insulation ring, 15 ... Cathode metal fitting, 16 ... Cathode cover, 17 ... Anode fitting, 18 ... plasma jet, 19 ... bubbles.

Claims (5)

Sodium were formed sacrificial sprayed coating on the inner peripheral surface - at the anode container sulfur battery, in cross section metallographic thickness 10μm units of the solution morphism film is a dense lamellar structure of at least three or more soluble morphism particles An anode container for a sodium-sulfur battery.   2. The sodium-sulfur battery anode container according to claim 1, wherein the sprayed coating has a thickness in a range of 30 μm to 80 μm. Sodium - A method of forming a thermal spray coating on the inner peripheral surface of the anode container sulfur battery, a Cr-Fe alloy powder spray metal powder contains 65% or more of Cr, O ₂ amount of the metal powder is 1.5% or less, and the metal powder is a lump powder obtained by pulverization with a particle diameter of 75 μm or less, and the spray gun is moved up and down while rotating the cylindrical anode container in the atmosphere. When plasma spraying, the flow rate of primary gas using argon gas of a spray gun is 30 to 45 l / min, the flow rate of secondary gas using hydrogen is 3.5 to 5.0 l / min, the metal powder The carrier gas flow rate using argon is 2.5 to 3.5 l / min, the spray gun output is 12 to 15 kW, the spray distance is 35 to 42 mm, the metal powder supply amount is 70 to 81 g / min, the anode The number of rotations of the container is 38 A method of forming a sprayed coating on the inner peripheral surface of an anode container for a sodium-sulfur battery, characterized by spraying in a range of 0 to 450 rpm and a spray gun traverse speed of 8 to 15 mm / sec . In the method for judging quality of the sprayed coating formed on the inner peripheral surface of the anode container for a sodium-sulfur battery, the section of the sprayed coating that has been cut and polished is chemically corroded, and the number of layered structures composed of sprayed metal particles is A quality determination method for a thermal spray coating formed on an inner peripheral surface of an anode container for a sodium-sulfur battery, wherein the quality is determined. 5. The inner peripheral surface of an anode container for a sodium-sulfur battery according to claim 4, wherein the number of the layered structures composed of the sprayed metal particles is determined as a good quality when there are three or more within a thickness of 10 μm. Quality judgment method of sprayed coating formed on the surface.

Images