JPS6131182B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention mainly relates to a tungsten carbide-based thermal spray material for producing a wear-resistant and/or corrosion-resistant thermal spray coating. Conventional tungsten carbide thermal spray materials are either a mixture of tungsten carbide powder and powders of other components such as cobalt metal powder, or granules of tungsten carbide and powders of other components such as cobalt metal powder. surface of tungsten carbide powder, powder of other components such as cobalt metal powder simply adhered with adhesive to the surface of tungsten carbide powder, or powder of components other than tungsten carbide powder such as cobalt metal powder A powder made by simply bonding tungsten carbide powder with an adhesive is used. However, all of these conventional thermal spray materials have the following drawbacks because the entire surface or a portion of the tungsten carbide particles are exposed. (b) During the flight of the powder during thermal spraying, the tungsten carbide in the melt powder comes into contact with air and carbon is oxidized and removed, reducing the quality of carbon in the sprayed coating and deteriorating the properties of the sprayed coating. (b) During thermal spraying, a portion of the thermal spray powder that collides with the thermal spraying surface is reflected and scattered, reducing the so-called yield of thermal spraying material. (c) During thermal spraying, not only other components such as cobalt but also a part of tungsten carbide are dissolved, and a large amount of eutectic alloy parts of tungsten carbide and other components are formed in the thermal sprayed coating, causing physical damage to the thermal sprayed coating. , deteriorating chemical properties. (d) In the deposition phenomenon of thermal spray particles during thermal spraying, the tungsten carbide collides with the surface of the sprayed object while being exposed, resulting in the bonding of tungsten carbide with each other within the sprayed film or the direct bond between the thermal spraying object and tungsten carbide. Part exists. The bonding force between tungsten carbide and the direct bonding force between the sprayed body and tungsten carbide are weak, and cracks and peeling phenomena tend to occur in the sprayed film, making it impossible to increase the thickness of the sprayed film. (e) When using a tungsten carbide self-fluxing alloy as a thermal spraying material, the entire surface or part of the tungsten carbide is exposed, so gas is generated due to carbon combustion during remelting, and foaming occurs on the coating surface. There are drawbacks such as the occurrence of blowholes and microholes. (f) Conventional tungsten-based thermal spray materials are usually applied only by plasma spraying, and it is not possible to create an excellent thermal spray coating by flame spraying using general, inexpensive equipment. In view of the above, the present inventors have found that there is little difference in carbon quality between the thermal sprayed material and the thermal sprayed coating, and that the yield of the thermal sprayed material is high, and that when used as a tungsten carbide-based self-fusing alloy in the thermal sprayed coating, blowholes and It is possible to create a sprayed coating with few microholes,
In addition, the present invention was arrived at as a result of intensive research aimed at developing a tungsten carbide thermal spray material that can produce an excellent thermal spray coating by thermal spraying due to fire. Fine powder or (b) Tungsten carbide-containing fine powder, abbreviated as tungsten carbide fine powder and other components in one particle, or/and one of tungsten, carbon and other elements.
A thermal spray material or a compound of one or more elements, or (c) a mixture of fine tungsten carbide powder and fine powder containing tungsten carbide, each coated with metal and/or other components by a plating method. Primary fine powder particles of particle size -15 microns + 3 microns of fine powder of tungsten carbide thermal sprayed material whose main component is the thermal sprayed material coated by the above-mentioned method are granulated, and further the fine powder particles are granulated with particle size -74.
The present invention provides a tungsten carbide thermal spray material which is granulated into a powder of micron+5 micron secondary particles. Tungsten carbide used in the present invention is a compound of tungsten and carbon.
It includes all combinations of tungsten and carbon such as W ₂ C and W ₃ C. Powder containing tungsten carbide means tungsten carbide and other components such as metal carbide,
Containing metal nitrides, metal oxides, etc. in one particle or/and compounds of tungsten, carbon, and one or more other elements, for example,
One particle contains WTiC, Co ₂ W ₄ C, FeW ₃ C, (CrFeWMo) ₂₃ C ₆ , etc. What is the plating method? Chemical vapor plating method, vacuum evaporation method,
This includes all gas phase plating methods such as electrolytic plating and sputtering, as well as liquid phase plating methods such as electrolytic plating and pressurized hydrogen reduction. Coating metals and/or other components by the plating method means coating the powder particles with metals such as cobalt, nickel, iron, chromium, aluminum, boron, or alloys of two or more of these metals. Or metal carbides other than tungsten carbide, boron compounds, metal oxides, metal nitrides, or other components such as synthetic resins, singly or in combination, in the form of alloys, compounds, and/or laminations, by the plating method. It is to cover it. Figure 1 is a micrograph at 1000x magnification of an example of the tungsten carbide sprayed material of the present invention, in which fine tungsten carbide powder is coated with cobalt metal by the plating method. It can be seen that it is plated with cobalt metal. Similarly, FIG. 2 is a micrograph at 1000x magnification of another example of the tungsten carbide thermal spray material of the present invention, in which fine tungsten carbide powder is completely electrified by plating nickel metal. 1
As in the case shown in the figure, it can be seen that the irregularly shaped tungsten carbide is completely plated with nickel metal. Figure 3 is a micrograph at a magnification of 1000 times of an example of the present invention in which fine tungsten carbide powder is coated with cobalt metal by the plating method and then granulated. It can be seen that the particles are plated with cobalt metal, and the particle size as a whole is suitable for thermal spraying. Figure 4 is a micrograph at 200x magnification of a cross section of a thermally sprayed coating using commercially available tungsten carbide-cobalt powder for comparison, showing that there are many pores and eutectic alloy areas. ing. Furthermore, FIG. 5 is a micrograph at a magnification of 200 times of a cross section of a thermally sprayed coating using the tungsten carbide-cobalt powder according to the present invention, and shows that there are fewer pores and eutectic alloy portions than in FIG. 4. It has high corrosion resistance and wear resistance as a thermal spray coating. The thermal spray material of the present invention has the following advantages compared to conventional products. (i) Since the thermal spray material is coated with metal and/or other components by the plating method, carbon is less likely to be oxidized and removed by oxygen in the air during the thermal spray flight. Therefore, performance deterioration due to a decrease in carbon quality in the sprayed coating can be suppressed. (ii) Of the thermal spray powder that collides with the thermal spray surface, fewer particles are reflected, resulting in a high yield of the so-called thermal spray material. (iii) Since the sprayed material is coated with metal or/and other components by plating method, the metal or/and other components will be dissolved first during thermal spraying. By melting the tungsten carbide, it is possible to suppress the dissolution of the tungsten carbide and create a melted coating with a small amount of eutectic portions between the tungsten carbide and the metal and/or other components. Therefore, deterioration in performance of the sprayed coating caused by the eutectic portion can be suppressed. (iv) In the deposition phenomenon of sprayed particles, since tungsten carbide is coated with metal and/or other components, there is no bonding between tungsten carbides or bonding between tungsten carbide and the sprayed body within the sprayed film. The bond between the particles in the sprayed film becomes strong, and even if the sprayed film is made thicker, cracks are less likely to occur, and the so-called thicker sprayed film can be made. (v) When using tungsten carbide-based self-fusing alloys, the entire surface of tungsten carbide is coated with metal and/or other components, so the amount of gas generated due to carbon combustion during remelting treatment. It is possible to create a sprayed coating with fewer blowholes and microholes without causing foaming on the surface of the coating. (vi) Powder A is the granulated powder obtained by granulating the fine powder coated on the fine powder, and Powder B is the powder coated on the coarse powder. It is coated with a metal that has a melting point lower than that of the tungsten carbide, and it is possible to obtain a thermal sprayed coating with less chemical component segregation than B powder, which uses coarse tungsten carbide powder, so the mechanical performance of the thermal sprayed coating is improved. It is stable and has improved corrosion and wear resistance. (b) Among the B powders that use coarse tungsten carbide, there are many powders in which the tungsten carbide itself hardly melts even if the coating metal melts during thermal spraying. The greater the mass of the unmelted tungsten carbide, the greater the force of repulsion, and it becomes difficult to prevent the repulsion only with the coating metal, which acts as a binder. Most of the tungsten carbide will fall off. However, in Powder A, each fine tungsten carbide powder is covered with a coating metal, so even if there is tungsten carbide that does not melt during thermal spraying, the rebound force is small and the coating metal acts as a binder to prevent rebound. . Also A powder and B
When comparing the powder as a single powder, powder A has a much larger surface area, and when the coating metal, which is a low melting point metal, melts, an apparently large amount of melt is generated, and the sprayed powder collides with the sprayed surface. Of these, fewer particles will be reflected. From the above, powder A has a higher yield of so-called thermal spray material. (c) The thermal sprayed coating using powder A has a much finer crystal structure than the thermal spraying coating using powder B because the coating metal exists as a binder between fine tungsten carbide particles. Since the finer the brittle tungsten carbide becomes, the more excellent the impact resistance is, it is clear that the thermal spray coating made of powder A has better impact resistance. (d) Tungsten carbide, the primary particle forming Powder A, is a fine powder, and the sprayed surface is much smoother and easier to finish than Powder B, which uses coarse-grained tungsten carbide. As mentioned above, methods for coating tungsten carbide fine powder, fine powder containing tungsten carbide, and mixed fine powder thereof with metal and/or other components include the vapor phase plating method and the liquid phase plating method. Phase plating methods include chemical vapor plating method, vacuum evaporation method, sputtering method, etc., and liquid phase plating methods include electrolytic plating method, pressurized hydrogen reduction method, etc., which are adopted in the present invention. There is no problem in doing so. Example 1 Thermal spray material made of fine tungsten carbide powder coated with cobalt by chemical vapor plating method, WC83%,
Co 17%, particle size -74+37 microns was sprayed onto SS41 spray body using a plasma spray machine. Also, under the same conditions, a commercially available WC-Co thermal spraying material (of the same quality, particle size, etc.) was sprayed onto each coating, and No. 4 silica sand was sprayed at an angle of 20° with compressed air at a pressure of 5 kg/cm ² for blast erosion resistance. As a result of testing, it was found to have approximately 1.5 times the blast erosion resistance of commercially available thermal sprayed coatings. Example 2 Ni, 35%, Si, manufactured by chemical vapor plating method
Powder of the present invention with 2.5%, B, 2.5%, Cr, 3%, balance WC-Co and Ni33%, Si, 2.0%, B, 2.0%,
A commercially available self-fusing alloy of 9% Cr and 50% WC-Co was sprayed onto two sludge transport pump sleeves using a plasma spraying machine under the same conditions. Figure 6 shows the relationship between the amount of wear and time. From FIG. 6, it can be seen that the product of the present invention has better wear resistance as measured by the maximum wear depth. Example 3 The thermal spraying material of the present invention, in which fine tungsten carbide powder was coated with nickel using a chemical vapor plating method, was thermally sprayed onto the shaft of a gland type slurry pump in a portion that would come into contact with the gland packing. The liquid to be conveyed is a liquid containing ammonium sulfate powder of 350 microns or less in a 5-15% sulfuric acid solution. Conventionally, a shaft made of SUS316 was used, and the continuous use time was about two weeks, but by applying the above thermal spraying treatment, it can be used continuously for more than two months. Example 4 WC83%, in which fine tungsten carbide powder was coated with cobalt by chemical vapor plating,
Primary fine powder particles containing 17% Co and having a particle size of -15 microns + 3 microns were granulated to produce secondary powder particles with a particle size of -74 microns + 37 microns. The performance of the secondary particles obtained in Example 4 is as follows. (1) Wear resistance of thermal sprayed coating Figure 7 shows the results of the abrasion test of the plasma sprayed coating. The abrasion test was performed by measuring the amount of sliding wear on an emery paper roll, and as shown in Figure 7, it was about 1.5 times that of the commercially available product, and about 1.5 times that of the powder coated with coarse powder.
It showed 1.3 times higher wear resistance. Particles with a particle size of less than 5 microns are not carried by plasma spraying or flame jets, but are scattered and deposited on the sprayed surface without adhering to it, thereby hindering the formation of a healthy sprayed coating on that surface. That is, there is a drawback that adhesion strength is reduced, and particles with a particle size exceeding 74 microns do not adhere tightly to the sprayed surface due to insufficient heating and are reflected, resulting in a reduction in the spraying yield of the powder. The test conditions were a wear rate of 17.3 m/min and a load of 2.0 kgcm ² . (2) Thermal spray yield The results of the thermal spray yield test are shown in Table 1. The yield was determined by plasma spraying on the center of the surface of a cylindrical base material of SUS420 with a diameter of 60 mm, length of 30 mm, and wall thickness of 3 mm, and a width of approximately 10 mm in the circumferential direction and a coating thickness of 0.4 mm. Calculated from the weight used. Table 1 shows the average values measured in 10 experiments for each powder material.

[Table] (3) Figure 7 shows the results of the wear resistance test of the tungsten carbide sprayed coating. That is, the thermal spraying material of the present invention manufactured and granulated according to Example 4 has the following properties: (A) Fine primary particles of tungsten carbide are coated with cobalt; It is less likely to be oxidized and removed by the oxygen contained therein, and therefore performance deterioration due to a decrease in carbon quality in the sprayed coating can be suppressed. As a single powder, the surface area is much larger than that of powder coated on coarse powder, and when Co, a low melting point metal, melts, an apparently large amount of melt is generated. There are fewer particles that
The yield of so-called thermal sprayed materials is increased. There is no bonding between tungsten carbide or bonding between tungsten carbide and the sprayed material in the sprayed film, and the bonds between particles in the sprayed film are strong, so even if the sprayed film is thick, cracks will not occur, resulting in so-called thermal spraying. The film can be made thicker. (B) Powder feedability is improved by coarsening fine primary particles, the mass of each particle is increased, and the tungsten carbide particles themselves are made finer to improve the spray surface. When the granulated powder collides with the tungsten carbide, the impulse per granulated powder is increased and the granulated powder is crushed and deposited, thereby improving the deposition yield of fine tungsten carbide particles. (C) If the environment in which the thermal spray coating is used causes wear of the fine powder, it is desirable to have a coat in which the fine powder of tungsten carbide is uniformly and densely distributed, and the present invention is effective in improving this wear resistance. It was found that this effect was achieved.

[Brief explanation of the drawing]

Figures 1 and 2 are micrographs (substituting for drawings) at a magnification of 1000 times of an example of the tungsten carbide thermal spray material of the present invention. Figure 1 shows that irregularly shaped tungsten carbide is completely covered with cobalt metal Indicates that it is plated. Similarly, FIG. 2 shows that the tungsten carbide is completely plated with nickel metal. FIG. 3 is a micrograph used as a drawing at a magnification of 1000 times when the tungsten carbide-based fine powder thermal spray material of the present invention is granulated. Figure 4 shows the magnification of the cross section of the sprayed coating using commercially available tungsten carbide cobalt powder.
A 200x magnification photomicrograph instead of a drawing. FIG. 5 is a 200x magnification photomicrograph of a cross section of a thermally sprayed coating that was sprayed using the thermal spraying material of the present invention. FIG. 6 is a diagram showing a comparison of the wear resistance of the sleeve of a sludge conveying pump between the product of the present invention and a commercially available product depending on usage time. FIG. 7 shows the results of the wear resistance test of the tungsten carbide sprayed coating according to Example 4. 1... Straight line showing the wear resistance characteristics of the product of the present invention, 2
... Straight line showing the wear resistance characteristics of conventional products, 3 ... Commercial product, 4 ... Powder coated on coarse powder, 5 ...
...A granulated powder coated with fine powder.

Claims (1)

[Claims] 1 (a) Tungsten carbide fine powder, or (b) tungsten carbide-containing fine powder, which is abbreviated as tungsten carbide fine powder and other components in one particle, or/and tungsten, carbon, and other components. Compounds of one or more elements or (c)
The main component is a thermal sprayed material in which a mixture of fine tungsten carbide powder and fine powder containing tungsten carbide is coated with metal and/or other components by a plating method, or a thermal sprayed material coated by the plating method. The primary fine powder particles of the tungsten carbide thermal spray material having a particle size of -15 microns + 3 microns are granulated, and the fine powder particles are further granulated into secondary particles with a particle size of -74 microns + 5 microns. Tungsten carbide thermal spray material.