JPH0317899B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a composite powder, and particularly to a composite powder for thermal spraying that is suitable for materials requiring properties such as wear resistance, corrosion resistance, heat resistance, and hardness. (Conventional technology and problems to be solved) Thermal spray powders conventionally used for materials that require properties such as wear resistance, corrosion resistance, heat resistance, and hardness include (a) Cr, Si, Ni group containing B, C and Fe or
Co-based self-fusing alloy, ( _{b )} Cr, Si ,B,
There are mixed powders mixed with Ni-based or Co-based self-fluxing alloys containing C and Fe. However, although it is acknowledged that the above-mentioned powders exhibit a certain degree of function for each purpose, they have the following disadvantages or drawbacks. That is, among the above powders, the powder made of the self-fusing alloy (a) is insufficient in terms of wear resistance and hardness. In addition, the mixed powder (b) is mixed with a self-fusing alloy and Cr ₃ C ₂ or WC during thermal spraying and in the process of feeding the powder to the thermal spraying machine.
Separation phenomena occur due to differences in particle size and specific gravity, etc., which tends to cause component segregation in the film.
It has drawbacks such as low adhesion yield of Cr ₃ C ₂ and WC, resulting in a porous film. The present invention aims to solve the above-mentioned drawbacks of the prior art and to provide a thermal spraying powder that produces a film that is highly uniform and dense, and that can achieve excellent wear resistance, corrosion resistance, heat resistance, hardness, etc. This is the purpose. (Means for Solving the Problems) In order to achieve the above object, the inventors of the present invention have developed powder composition, properties, and
As a result of multifaceted research on manufacturing methods, etc., we have discovered that not only are hard particles uniformly dispersed in the metal phase, but we have also created a new product in which the hard particles and part of the metal phase are partially bonded by melting reaction. We succeeded in obtaining a composite powder with a complex structure. That is, the present invention can be summarized as follows.
It consists of 10 to 50 vol% of hard particles of 100 μm and 90 to 50 vol% of a metal phase which is a matrix alloy phase, and the hard particles are chromium carbide or tungsten carbide and the metal phase is a self-fusing alloy, and a part of the hard particles and the metal Part of the phase is partially bonded by melting reaction, and hard particles are uniformly dispersed in the metal phase.
In addition, when the hard particles are chromium carbide, the composition of the composite powder is Cr: 16 to 42 wt%, Si: 1.4 to 4.5 wt%,
B: 1.4 to 4.5 wt% and C: 1.4 to 5.1 wt%,
The remainder has a composition of one or more of Ni, Co, and Fe, and when the hard particles are tungsten carbide, Cr: 4 to 20 wt%, Si: 1.0 to 4.5 wt%,
B: 1.0-4.5wt%, C: 0.7-3.9wt% and W: 9
The gist of the present invention is a composite powder for thermal spraying, characterized in that it has a composition of 47 wt% and the remainder is one or more of Ni, Co, and Fe. The present invention will be explained in more detail below. Matrix alloy phase (metallic phase) in the present invention
must be a self-fusing alloy, and the hard particles dispersed therein must be either chromium carbide or tungsten carbide. The reason is as follows. The self-fusing alloy is an alloy containing at least a predetermined amount of B and Si as described below in a metal consisting of one or more of Ni, Co, and Fe. This supersaturated solid solution of B and Si significantly lowers the temperature at which the liquid phase appears, and furthermore, B and Si also serve as a flux. For this reason, when a film sprayed with a self-fusing alloy is heated and held at a certain temperature (usually 950-1050°C) (called melting treatment or fusing), the appearance of a liquid phase eliminates the pores in the film, and the diffusion effect strengthens the film. and the bonding strength with the base material increases significantly. Furthermore, due to the flux action, it has a cleaning effect to eliminate oxides generated during thermal spraying that are present in the coating, and also prevents oxidation of the coating during heating. In addition to B and Si, such self-fusing alloys usually contain Cr to provide oxidation and corrosion resistance, and C to increase hardness and provide wear resistance. Self-fusing alloys with this effect are B and Si.
Because of the need to contain supersaturated carbon dioxide, it is usually produced by an atomizing method or rapid cooling casting from a molten state into a mold. Incidentally, in order to further improve the wear resistance of self-fluxing alloys, carbide is generally added, and a mixing method is adopted as the method for this addition. This is because the sintering method, which is a common production technology for thermal spray powder, causes precipitation of B and Si during sintering, which loses the effect of the self-fluxing alloy mentioned above, and composite atomization, in which carbide is added during atomization. This is because it is difficult to atomize the molten metal of the self-fusing alloy while adding carbide at a temperature at which the self-fusing alloy does not solidify and the carbide does not decompose. When thermal spraying is performed using a mixed powder of a self-fluxing alloy and carbide produced by such a mixing method, the following problems arise. In other words, the wear resistance does not improve much. The reason for this is that in the mixing method, the grain size of the carbide added is similar to the size of the self-fluxing alloy, and due to the difference in specific gravity, segregation occurs during thermal spraying or in the feeder of the thermal spraying equipment, resulting in a uniform coating. This is to prevent it from being dispersed. In the worst case, this segregation may cause cracks in the film of large workpieces such as rolls after melt processing. The present invention solves the problems of conventional mixed powders by creating a composite powder with a specific particle bonding state as described above, and evenly disperses carbide in the self-fusing alloy film. This made it possible to improve the wear resistance of When the hard particles are chromium carbide, the material has excellent oxidation resistance at high temperatures and also has good wetting (compatibility) with self-fusing alloys. Furthermore, when the hard particles are tungsten carbide, they have high hardness and have good wetting (compatibility) with self-fusing alloys. However, each of the other carbides has problems in terms of properties or cost. For example, titanium carbide has the same oxidation resistance and hardness as tungsten carbide, but because it has poor wettability (compatibility) with self-fusing alloys, gas is generated during compounding or melting processing, resulting in the formation of a film. becomes unhealthy. The metal phase and hard particles must be mixed in a predetermined ratio, and the hard particles with a particle size of 1 to 100 μm
Preferably, the content is in the range of 10 to 50 vol%, and the metal phase is in the range of 90 to 50 vol%. If the ratio and particle size are outside this range, the properties of thermal spray powder, i.e., at least one of wear resistance, corrosion resistance, heat resistance, and hardness, will be insufficient. When the particle size of the particles is larger than 100 μm, it becomes difficult to uniformly disperse them in the metal phase consisting of a self-fusing alloy, and it is impractical to obtain hard particles smaller than 1 μm due to high cost. In addition, the amount of hard particles added is less than 10vol% (the amount of metal phase is less than 90vol%).
The effect of adding hard particles (more than 50 vol %) will be insufficient, and conversely, if more than 50 vol % of hard particles are added, the effect of the self-fusing alloy, which is the metal phase, will be reduced. Since the composite powder of the present invention is mainly used for powder flame spraying or plasma spraying, the particle size is suitably 150 to 44 μm, preferably 125 to 20 μm. The composition of the composite powder of the present invention is as follows depending on whether chromium carbide or tungsten carbide is used as the hard particles. Cr: 16-42wt%, Si: 1.4-4.5wt%, B:
1.4 to 4.5 wt% and C: 1.4 to 5.1 wt%, with the remainder consisting of one or more of Ni, Co, and Fe, and consisting of a metal phase of chromium carbide and a self-fusing alloy. Composite powder. Cr: 4-20wt%, Si: 1.0-4.5wt%, B:
1.0-4.5wt%, C: 0.7-3.9wt% and 9-47wt
%, with the balance consisting of one or two of Ni, Co, and Fe, and the composite powder consists of tungsten carbide and a metal phase of a self-fusing alloy. The reason for limiting the composition of the composite powder as described above is as follows. First, the reason why the amounts of Cr and C are different between when chromium carbide is used and when tungsten carbide is used is that the amount of garbite added is calculated as 10 to 50% by volume. If the carbide content is less than 10% by volume, the effect of adding carbide (improving wear resistance) cannot be obtained, and if it is more than 50%, it becomes difficult to melt the sprayed coating. If the amount of B and Si is less than each lower limit value, melt processing becomes impossible (flux action disappears), and if it is more than the upper limit value, the amount of liquid phase generated during melt processing is too large, making melt processing work difficult. (for example,
In the case of a flat plate, the film will run off). The minimum amount of Cr is the amount necessary for corrosion resistance and oxidation resistance, and when chromium carbide is used, the amount of Cr due to this addition is added. The amount of C is in the range of the amount introduced by the addition of carbide. In addition, in the present invention, since a decarburization phenomenon occurs, the lower limit of the range of C is set to be low. The composite powder of the present invention comprising such a metal phase and hard particles is comprised of composite alloy particles in which hard particles are dispersed in a metal matrix in a state where some of the hard particles have undergone a melting reaction. The structure of each particle of this composite powder is
For example, when tungsten carbide is used as the hard particles, as shown in Figure 1, and when chromium carbide is used, as shown in Figure 2, the hard particles 3 are uniformly distributed in the metal phase 2. The metal phase 2 is dispersed, and exhibits a composite structure in which a molten phase 4 is partially formed at the interface between the metal phase 2 and the hard particles 3. A powder with such a composite structure is composed of a self-fusing alloy powder 5 and a chromium carbide powder 6, as shown in the conventional product shown in FIG.
This is completely different from the simple mixture of chromium carbide powder 6 and the other conventional products shown in FIG. It has a different structure from the one made composite by coating. The composite powder of the present invention is in a composite state by partially reacting carbide with a metal matrix. Compared to thermal sprayed coatings obtained by thermal spraying using granulated composite materials, the coating has far superior uniformity, density, and abrasion resistance. Composite powders of such excellent quality are, for example,
The raw material powder, which is prepared by mixing and granulating metal or alloy powder and hard particles in an appropriate ratio, is melted in a plasma arc, rapidly cooled on the cooling roll surface, processed into a composite metal quenched ribbon, and then pulverized and classified. can be obtained. Alternatively, a metal or alloy powder is melted in a plasma arc to form a molten pool on the surface of a cooling roll rotating at a low speed, and hard particles are supplied into the molten pool before the pool is cooled to perform rapid cooling. to form a composite metal quenched ribbon, which is similarly crushed.
It can also be obtained by classification. (Example) Next, an example of the present invention will be shown. Example 1 A raw material powder prepared by stirring and mixing 15 parts by weight of Cr ₃ C ₂ with a purity of 99% or more with 85 parts by weight of a Ni-based self-fusing alloy having the composition shown in Table 1 was melted in a plasma arc.
This was quenched on the roll surface of a cooling roll placed below a plasma torch to process it into a quenched composite metal ribbon, followed by crushing and classification (grading) to obtain a composite alloy powder for thermal spraying. Table 2 shows the composition and particle size of the composite alloy powder obtained. Next, using the above composite alloy powder as a thermal spraying material, a thermal spray coating was created under the thermal spraying conditions shown in Table 4,
Thereafter, test pieces were subjected to fusing (melting) treatment under the conditions shown in Table 4, and the hardness (Hv) was measured and the Ohkoshi wear test (WS) was conducted to evaluate the film characteristics. The results are shown in Table 3. For hardness measurements, thermal spraying to a thickness of 0.3 mm on regular steel materials, fusing treatment, cutting, and polishing were performed using a microhardness meter DMH-2 manufactured by Matsuzawa Seiki Co., Ltd.
The cross-sectional hardness Hv (0.3) was measured using a mold with a load of 300 g. In addition, for the Okoshi type wear test, after thermal spraying and fusing treatment to a thickness of 0.3 to 0.5 mm on a regular steel plate, the surface of the thermal sprayed coating was machined and wrapped to a surface roughness of JIS standard 0.5S. A wear test was conducted using an Okoshi type abrasion tester. The test conditions were: mating material SUJ-2 (bearing steel), load 18.9Kg,
The conditions were a wear rate of 0.9 m/s, a friction distance of 600 m, and no lubricating oil was used. Example 2 The same procedure as in Example 1 was carried out using a raw material powder prepared by stirring and mixing 15 parts by weight of Cr ₃ C ₂ with a purity of 99% or more with 85 parts by weight of a Co-based self-fusing alloy having the composition shown in Table 1. A composite alloy powder for thermal spraying was obtained using the manufacturing method described above. The composition and particle size of the obtained composite alloy powder are also listed in Table 2. Next, thermal spraying was evaluated under the same conditions as in Example 1 using the above composite alloy powder as a thermal spraying material. The results are also listed in Table 3. Example 3 Elementary metals (metal Cr, metal Cr,
For 85 parts by weight of metal Si, NiB alloy, metal Ni,
15 parts by weight of Cr ₃ C ₂ with a purity of 99% or more is mixed and pulverized in an attritor, and a binder (resitop: 5 to 10% phenol and 30 to 40% methanol) is added to this powder.
A composite alloy powder for thermal spraying was obtained by the same manufacturing method as in Example 1, using the powder obtained by adding 6 parts by weight of (containing) and granulating it with a Henschel mixer as a raw material. The composition and particle size of the obtained composite alloy powder are also listed in Table 2. Next, thermal spraying was evaluated under the same conditions as in Example 1 using the above composite alloy powder as a thermal spraying material. The results are also listed in Table 3. Comparative Example 1 Thermal spraying was evaluated under the same conditions as in Example 1 using 100 parts by weight (single) of a Ni-based self-fusing alloy having the composition shown in Table 1. The results are also listed in Table 3. Comparative Example 2 The same conditions as in Example 1 were carried out using a powder obtained by simply mixing 15 parts by weight of Cr ₃ C ₂ with a purity of 99% or more with 85 parts by weight of a Ni-based self-fusing alloy having the composition shown in Table 1. Thermal spraying was evaluated. The results are also listed in Table 3. Comparative Example 3 The same conditions as in Example 1 were carried out using a powder obtained by simply mixing 15 parts by weight of Cr ₃ C ₂ with a purity of 99% or more with 85 parts by weight of a Co-based self-fusing alloy having the composition shown in Table 1. Thermal spraying was evaluated. The results are also listed in Table 3.

【table】

[Table] (Note) Raw material powder numbers correspond to the numbers in Table 1.

[Table] (Note) Raw material powder No. is the No. in Table 1.
It corresponds to

【table】

【table】

[Table] As is clear from Table 3, Example 1 of the present invention
In all cases No. 3 to 3, films of high purity and excellent wear resistance were obtained. On the other hand, all of Comparative Examples 1 to 3 have low hardness and poor wear resistance. Especially when hard particles are dispersed in a self-fusing alloy (Comparative Example 2,
3) Although the hardness is improved to some extent compared to Comparative Example 1 which does not contain hard particles, the wear resistance is hardly improved because the hard particles are simply mixed. In addition, when we observed the structure of the particle cross section of the composite alloy powder obtained in each of the above examples, it was found that Cr ₃ C ₂ particles were uniformly distributed in the matrix metal phase, and a molten phase was partially recognized at the interface between the two. condition was observed. Figure 5 is a photograph showing the structure of a composite powder particle of a Ni-based self-fusing alloy and chromium carbide. At the boundary between the self-fusing alloy and chromium carbide, the concentration curves of Ni and Cr each have a bending point, and the concentration gradient increases. For some reason,
It can be seen that a portion of the sample undergoes a melting reaction. Example 4 Using the same manufacturing method as Example 1, using a raw material powder prepared by stirring and mixing 35 parts by weight of WC with a purity of 99% or more with 65 parts by weight of a Ni-based self-fusing alloy having the composition shown in Table 1. A composite alloy powder for thermal spraying was obtained. The composition and particle size of the composite alloy powder obtained are shown in Table 2. Next, thermal spraying was evaluated under the same conditions as in Example 1 using this composite alloy powder as a thermal spraying material. The results are also listed in Table 3. Table 3 shows that a film with high hardness and excellent wear resistance was obtained. (Effects of the Invention) As detailed above, the composite powder of the present invention has hard particles made of chromium carbide or tungsten carbide uniformly dispersed in a metal phase made of a self-fusing alloy, and a part of the hard particles. Part of the metal phase is partially melted and reacted and bonded together, so the coating obtained by thermal spraying using this should have excellent coating properties such as abrasion resistance, corrosion resistance, heat resistance, and hardness. becomes possible.

[Brief explanation of the drawing]

Figures 1 and 2 are explanatory diagrams showing the structure of individual particles of the composite powder in which hard particles are dispersed in the present invention, respectively. Figure 1 shows the case where tungsten carbide is dispersed, and Figure 2 Fig. 3 and Fig. 4 are explanatory diagrams showing the mode of conventional mixed powder, Fig. 3 shows a case where chromium carbide powder and self-fusing alloy are mixed, and Fig. 4 shows a case where chromium carbide is dispersed. Figure 4 shows the case of granulated composite powder in which the surface of self-fusing alloy powder is coated with chromium carbide powder using a binder, and Figure 5 shows the case of composite powder particles of Ni-based self-fusing alloy and chromium carbide. This is a photo showing the structure. 1... Composite alloy powder, 2... Metal phase, 3...
Cr ₃ C ₂ or WC powder, 4... surface molten phase, 5...
Self-fusing alloy, 6...Chromium carbide.

Claims (1)

[Claims] 1. 10 to 50 vol% of hard particles with a particle size of 1 to 100 μm and a matrix alloy phase (hereinafter abbreviated as metal phase) 90 to 50 vol%
50vol%, the hard particles are chromium carbide and the metal phase is a self-fusing alloy, and a part of the hard particles and a part of the metal phase are partially bonded by melting reaction, and the hard particles are It is uniformly dispersed in the metal phase, and the composition of the composite powder is Cr: 16 to 42 wt%,
Si: 1.4-4.5wt%, B: 1.4-4.5wt% and C: 1.4
A composite powder for thermal spraying, characterized in that it contains ~5.1wt%, and the remainder consists of one or more of Ni, Co, and Fe. 2 Consisting of 10 to 50 vol% of hard particles with a particle size of 1 to 100 μm and 90 to 50 vol% of a matrix alloy phase, where the hard particles are tungsten carbide and the metal phase is a self-fusing alloy, and a part of the hard particles and the metal phase A part of the composite powder is partially melted and reacted, hard particles are uniformly dispersed in the metal phase, and the composition of the composite powder is
Cr: 4-20wt%, Si: 1.0-4.5wt%, B: 1.0-
4.5wt%, C: 0.7-3.9wt% and W: 9-47wt%
A composite powder for thermal spraying, characterized in that the remainder consists of one or more of Ni, Co, and Fe.