KR100276331B1 - The spray coating for cermet carbide - Google Patents

Abstract

PURPOSE: A spray coating method of ceramic metal is provided to improve surface processability and productivity by coating large-sized carbide powder on the bottom part of the coating layer and coating small-sized carbide powder on the upper part of the coating layer. CONSTITUTION: The spray coating method of ceramic metal comprises the step of coating carbide powder of a particle size ranging from 3 to 5μm on the lower part of the coating layer; coating a mixture of carbide powder where carbide powder of a particle size ranging from 3 to 5μm and carbide powder having a particle size below 2 μm are blended in a ration of 1:1 on the surface of the first coating layer; coating carbide powder having a particle size below 2μm on the surface of the second coating layer. The depth of the upper coating layer is 60μm.

Description

Carbide metal cermet thermal spray coating method

The present invention relates to a method of thermal spray coating with a thermal spraying material made of carbide-metal on a material widely used in various fields of the steel industry, aviation industry, paper industry, and the like. It relates to a more easy spray coating method.

In general, a material widely used in various fields of the industry is mainly used by spray coating a thermal spraying material of carbide metal to give mechanical properties such as wear resistance. Carbide, which is widely used as the thermal spraying material, includes tungsten carbide, chromium carbide, titanium carbide, zirconium carbide, and the like, and nickel, cobalt, and the like are mainly used as a binder. In this case, nickel and cobalt may be used in the form of alloys of metals such as chromium and aluminum, if necessary, and iron-based alloys may also be used as binders as necessary. The material coated with the carbide-metal spray material is usually used directly in a spray coated state, but may be used by buffing to lower the surface roughness or mirror-hardening. The mirror processing refers to processing the surface of the coating to a very low roughness (usually Rmax 1μ or less), and after polishing, becomes mirror-like and high reflectivity. In the case of such mirror processing, after coating, the coating surface should be cut off by more than 0.1mm. Therefore, the additional burden for processing during the entire coating cost is 20-40% higher than in the case without mirror processing. There is a problem.

On the other hand, there are a number of methods for mirror surface processing, such as cutting the coating using silicon carbide-based black diamond abrasive stone, or using a silicon roll or diamond-coated film in the belt type to pressure the rubber roll At the same time, there is a method of processing while rotating the film. In the case of using the abrasive stone, when the processing speed is increased or a lot of pressure is applied, the vicinity of the abrasive stone surface is easily broken, and the processing surface itself is often not clean. In addition, in the case of using the film method, because the film is processed while rotating, the new surface always comes in contact with the coating surface, so that a clean surface can be obtained compared to the case of using abrasive stone, but compared to the case of using abrasive stone There is a costly disadvantage.

As described above, when the conventional carbide metal thermal spray material is coated on the material, when a constant roughness is required for the material, buffing or mirror processing requires long-term surface processing during post-treatment, resulting in low productivity and increased manufacturing cost. have.

Accordingly, the present invention has been made in order to solve the conventional problem, by spraying coating on the base material by controlling the particle size of the thermal spraying material in the thermal spray coating using carbide metal as a thermal spraying material is excellent in productivity The purpose is to provide a thermal spray coating method that can lower the manufacturing cost.

Figure 1 (a) is a schematic diagram showing a shape in which a large carbide coating layer is scraped off by abrasive grains.

(b) is a schematic diagram showing the shape in which the coating layer of the small carbide is carved out by the abrasive grains.

Figure 2 (a) is a schematic diagram showing a coating method according to the present invention.

(b) is a schematic view showing another coating method according to the present invention.

* Explanation of symbols for main parts of the drawings

1 carbide 2 abrasive grain

3: coating object 4: metal

5: coating layer of carbide of small particle

6: coating layer of large grain carbide

7: coating layer in which large particles and small particles of carbide are mixed

In order to achieve the above object, the present invention provides a method for thermally coating a coating layer requiring surface polishing by using a thermal spraying material made of carbide-metal, and having a carbide particle size coated a near thermal spraying material at a lower portion of the coating layer. The upper side relates to a carbide-metal cermet thermal spray coating method for coating a thermal spraying material having a small carbide particle size.

Hereinafter, the present invention will be described in detail.

Although the spraying method to which this invention is applied can be any, More preferably, it is a high speed flame spraying. In other words, in the coating of carbide and metal, the melting temperature of carbide is much higher than that of metal, although it is different depending on the type of carbide. In the case of plasma spraying, the temperature of plasma rises above 10000 ℃ in most cases. Since both the carbide and the metal are melted and attached to form a coating layer, it is not meaningful to apply the present invention. However, since the temperature varies depending on the position at which the coating powder is supplied, the present invention can be applied when the coating operation is performed by setting conditions in which carbides are not melted but only metal is melted. In the case of high-speed flame spraying, the flame temperature is around 3000 ℃, but the melting temperature of carbides may be higher or lower than that. Since it is attached, it is easy to apply the coating method of the present invention. When the thermal spraying coating is applied by applying the thermal spraying method, the carbide is not melted or only partially melted, and thus the size of the carbide greatly affects the roughness of the coating layer. That is, the smaller the carbide particles in the coating powder, the lower the roughness of the coating layer can be obtained, and the polishing treatment becomes easier.

In the present invention, since the lower part of the coating layer does not have much correlation with the surface roughness using the above characteristics, it is possible to coat a low-cost spray material, that is, a thermal spray material having a large carbide particle size, and the upper surface of the carbide particle is considered Coat a small thermal sprayed material. More specifically, as shown in FIG. 1A, when the particle size of the carbide 1 of the coating layer is larger than that of the abrasive grain 2, the carbide 1 having a higher hardness is used during polishing. Since the carbides are broken or the carbides 1 are not cut by the abrasive grains 2 and are likely to fall off, the place is pitted, and the polishing surface tends to be rough. However, when the carbide 1 of the coating layer is small, the carbide 1 is not broken by the abrasive particles 2 as shown in FIG. 1 (b), and the abrasive surface is not rough because the particles are small even if they are separated. Generally, there are several advantages when coating with carbide-cermet powder with small carbide particles, but smaller carbide particles are more expensive, and it is difficult to produce a mixture of carbides and metals evenly when forming a thermal spray powder. The present invention is to change the carbide particle size of the coating layer as described above because it is difficult because the price is expensive.

As described above, if a thermal spray material having a large carbide grain size is applied to the upper portion of the coating layer, and a thermal spray material having a relatively small carbide grain size is applied to the lower portion of the coating layer, the surface processing becomes easier and economical, but more preferably, FIG. As shown in a), the upper surface of the carbide (1) is coated with a thermal sprayed material having a particle size of 3 to 5 µm and a lower thermal sprayed material having a thickness of 2 µm or less.

As the size of the coating screen carbide is changed as described above, the characteristics of the coating are partially changed, so it is better to coat the spray material with a smaller and smaller carbide particle size toward the upper portion of the coating layer. More preferably, as shown in FIG. 2 (b), a sudden change in characteristics is formed by forming a coating layer 7 in which a small powder and a large powder are mixed in the middle of the upper and lower coatings. It can also be mitigated.

At this time, a spray material having a carbide particle size of 3 to 5 µm is mixed in the lower portion of the coating layer, and a spray material having a spray material of 3 to 5 µm and a spray material having a thickness of 2 µm or less is coated on the upper portion thereof.

The proper mixing ratio of the mixed spray material coated in the middle of the coating layer is good to use a lot of spray material of 2㎛ or less in consideration of the surface quality, it is good to use a spray material of 3 ~ 5㎛ considering the manufacturing cost, the overall effect Considering the overall characteristics of using a thermal spraying material having a mixing ratio of 1: 1 is good.

In the above spray coating method, the thickness of the upper coating layer is preferably 60 µm or more in order to make the roughness Rmax 0.2 or less after polishing during polishing.

Hereinafter, the present invention will be described in more detail with reference to the following examples.

EXAMPLE

Experiments were conducted on tungsten carbide-cobalt based alloys, which most often require post-coating polishing. The composition of the coating powder was 88% WC-12% Co, and the coating test piece was made of a low carbon steel pipe with a diameter of 12cm and a thickness of 3mm, and the surface roughness was blasted with # 20 alumina powder as a pretreatment before coating. It was set to micrometer. The coating was carried out with the JP-5000 coating machine, which is a high speed spraying machine, and the coating parameters were recommended by the powder manufacturer, and the coating parameters were coated under the same conditions due to the small difference in the coating parameters according to the carbide particle size. The coated pipe was bitten by a lathe, and the surface was polished with diamond abrasive stone. The same variables as the rotational speed, the moving speed, and the pipe rotational speed were polished. After the surface roughness was measured using a roughness in the middle of coating and polishing, it is shown in Table 1 below.

At this time, Table 1 shows the roughness according to the coating thickness, coating roughness, polishing thickness and polishing thickness of the comparative material and the invention material. Comparative material 1 is coated with a powder having a carbide particle size of 3-5 μm.

Inventive material (1) is a case in which 100 µm is coated with a large carbide size powder and 100 µm coated thereon with a small carbide size in the same manner as shown in FIG. The comparative material 2 is a case where the size of the carbide is coated only with a spray powder having a size of 2 μm or less.

Inventive material (2) is a coating layer as shown in FIG. 2 (b), which is coated with 100 탆 coated with a large carbide size powder and again coated with 50 탆 coated with a large carbide powder and a small powder. It is the case that 50㎛ coating with small size powder.

TABLE 1

As shown in Table 1, the comparative material (1) could be obtained roughness of about Rmax.2 by polishing about 100㎛, while the comparative material (2) was able to obtain roughness of about Rmax 0.2 by polishing about 40㎛ There was a problem of rising manufacturing costs. On the other hand, inventive material (1, 2) was able to obtain a roughness of Rmax 0.2 when polished to 60㎛. In other words, the same polished state can be obtained even when half the thickness of the tongue is processed compared with the conventional method. Therefore, the coating according to the present invention is much more economical since only 50% of the thickness of the coating to be polished is applied when the thickness of the final coating is the same, and at least 10 hours is required when processing the actual roll. Considering this, machining time can be saved by 50%.

As described above, the present invention can provide a thermal spray coating method to reduce the use amount of the thermal spraying material having a smaller carbide particle size compared to the conventional material, and also to reduce the surface polishing thickness, thereby improving productivity and reducing manufacturing costs. The provided method has a useful effect that can be applied to various industrial fields.

Claims (4)

In the method of spray coating the surface of the coating layer requiring a surface polishing using a carbide-metal thermal spraying, the coating layer is coated with a thermal spraying material having a carbide particle size of 3 ~ 5㎛ on the bottom, the carbide particle size on the top Carbide-metal surfet spray coating method characterized by coating a thermal spraying material having a thickness of 2 μm or less The spray coating material according to claim 1, wherein the coating layer is coated with a thermal spraying material having a carbide particle size of 3 to 5 µm on the lower surface, and a thermal spraying material having a thermal spraying material having a carbide particle size of 3 to 5 µm and a thermal spraying material having a thickness of 2 µm or less. After coating, the top of the method characterized in that the coating of the thermal spraying material having a carbide particle size less than 2㎛ The method of claim 2, wherein the mixed thermal spraying material comprises a 1: 1 mixture of a thermal spraying material having a carbide particle size of 3 to 5 µm and a thermal spraying material having a thickness of 2 µm or less. The method of any one of claims 1, 2 and 3, wherein the upper coating layer is coated with a spray material having a carbide particle size of 2 µm or less to a thickness of 60 µm or more.