JPS63227757A - Method for thermally spraying wear-resistant ceramics - Google Patents

Abstract

PURPOSE:To form a ceramics thermally sprayed layer having high hardness and excellent in wear resistance, by mixing a composite grain powder in which TiC and metal are integrally compounded with a prescribed amount of TiC powder and by thermally spraying a base material with the resulting powder mixture. CONSTITUTION:A composite grain powder in which TiC and a metal such as Ni, Co, Ni-Cr alloy, etc., are integrally compounded is previously prepared. Subsequently, the grain powder mixture is mixed with a TiC powder so that TiC powder comprises 10-50wt.%. Then, the resulting powder mixture is thermally sprayed on a base material to form a wear-resistant ceramics layer. In this thermally spraying method, it is desirable that thermally spraying method of this invention is applied to an undercoat thermally sprayed layer consisting, e.g., of an Ni-base alloy such as Ni-Al alloy, Ni-Cr alloy, etc., which is previously formed on a substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention uses ceramics-based materials to improve surface wear resistance, heat resistance, heat insulation, and other properties in piston cylinder bores for internal combustion engines and various other members. This relates to the method of thermal spraying on materials, especially T, which has excellent wear resistance.
The present invention relates to a method of forming a sprayed layer mainly composed of iC.

Prior art Among various ceramic materials, TiC (titanium carbide) is a high melting point material, has high hardness, and is known as a material with excellent heat resistance, abrasion resistance, corrosion resistance, and oxidation resistance.
Therefore, TiC has conventionally been used mainly as a sintering material in applications where the above-mentioned performance is required.

By the way, generally ceramic materials obtained by sintering method (
Sintered ceramics) have the problem of lacking strength, especially toughness, but on the other hand, they do not have the aforementioned wear resistance, heat resistance, oxidation resistance,
In many cases, corrosion resistance is sufficient if only the surface layer is sufficient, so it is often desirable to locally coat only the surface layer of a base material made of metal etc. with ceramics. Thermal spraying is often used. However, TiC has a melting point (approximately 3160°C) and a sublimation point of 3300°C, which is relatively close to each other. Therefore, when TiC itself is directly sprayed by plasma spraying, sublimation and decomposition easily occur, and the base It was often difficult to form a TiC coating layer that adhered to the surface of the material.

On the other hand, as one of the thermal spraying methods for ceramic materials, Japanese Patent Application Laid-Open No. 59-64766 discloses that the surface of ceramic powder particles is coated with a metal such as GO or Ni in advance, and then the coated powder particles are thermally sprayed. Accordingly, a method has been proposed in which the thermal spray 1 is formed by the bonding force of metals. Therefore, with respect to TiC, if TiC particles are coated with a metal such as Ni or CO in advance using this method and the powder is thermally sprayed, the TiC will be wrapped in the metal, making it difficult to decompose or sublimate. The bonding force of v! is sufficient to form on the base material. It is thought that it is possible to make it wear i.

Problems to be Solved by the Invention According to the method proposed above, GoYN is applied to TiC powder particles.
When a metal such as 1 is coated and sprayed onto the base material 1, the sprayed layer 3 becomes a state in which TiC particles 4 are dispersed in a metal phase 5 such as CO or N1, as shown in FIG. Therefore, the hardness of the sprayed layer 3 itself is Hv
(approximately 3,000), rather than Ni and G.
Hardness close to that of the metal layer itself, such as o, Hv500~1
TiC
When used alone, the wear resistance is not high and only the same level of wear resistance as Ni or Go can be obtained. Of course, if the coating thickness of metal such as Ni or Co on TiC powder particles is reduced, the amount of TiC dispersed in the sprayed layer will increase and the hardness of the sprayed layer will also increase. surface coati.

It is difficult to significantly reduce the thickness of the thermally sprayed layer, and there are restrictions on its thinning. Therefore, with the method proposed above, it is not possible to increase the TiC dispersion in the thermally sprayed layer more than necessary, and the hardness of the thermally sprayed layer Furthermore, it was not possible to sufficiently improve the wear resistance.

In this way, in the proposed method, T
Even when using iC, it has been difficult to fully exhibit its properties and form a thermal sprayed layer with excellent wear resistance.

This invention was made against the background of the above-mentioned circumstances.
The purpose is to provide a method for forming a thermal sprayed layer with high hardness and excellent wear resistance by fully demonstrating the functions of TiC while suppressing sublimation and decomposition of TiC. be.

Means for Solving the Problems The thermal spraying method for wear-resistant ceramics of the present invention is based on TiC
When forming the sprayed layer mainly composed of TiC,
A powder made of composite particles in which TiC and metal are integrated is prepared, and this composite particle powder and TiC powder are combined into TiC
The method is characterized in that the powder is mixed so as to account for 10 to 50 wt%, and the mixed powder is thermally sprayed onto a substrate.

Here, the metals in the composite particles include Co, Ni,
One or more selected from Ni-Cr alloys can be used.

Function: In the method of the present invention, TiC, Ni and Qo-
1 Powder consisting of composite particles that are integrated with metal such as Ni-Cr alloy, and TiC powder (powder of TiC alone)
The mixture is then sprayed onto the base material. At this time, since TiC in the TiC-metal composite powder particles is covered with metal, it does not easily sublime and decompose. Furthermore, although TiC powder sublimes and decomposes more easily than TiC in composite powder, it is immediately engulfed by the metal of the composite powder when it reaches the base material, so it is less effective than spraying TiC powder alone. It is extremely difficult to sublime and decompose, and most of it is sufficiently captured and remains in the sprayed layer.

In other words, as TIC in the sprayed layer, both TiC in the IC-metal composite powder and TiC due to the TiC powder are dispersed, and the structure of the sprayed layer is composed of these TiC
The particles appear to be bonded by metal derived from the TiC-metal composite powder. Therefore, compared to spraying only TiC-metal composite powder, TiC-
By spraying TiC powder mixed with the metal composite powder, the amount of TiC dispersed in the sprayed layer increases by the amount of TiC powder, so the hardness of the sprayed layer is only that of the TiC-metal composite powder. The hardness is closer to that of TiC itself than when TiC is used, and as a result, the wear resistance of the sprayed layer is also improved.

Here, if the proportion of TiC powder mixed into the TiC metal composite powder exceeds 50%, the proportion of TiC-metal composite powder will be relatively small, so that the TiC powder that has reached the base material during thermal spraying will be mixed into the composite powder. The TiC powder cannot be sufficiently enveloped by the metal powder, which increases the rate of sublimation and decomposition of the TiC powder, creating a large number of pores in the sprayed layer, reducing the hardness of the sprayed layer as a whole and reducing wear resistance. Resulting in.

On the other hand, if the proportion of TiC powder is less than 10%, the T
The amount of iC dispersed is small, that is, the amount of TiC dispersed increases only slightly compared to when only TiC-metal composite powder is used, and therefore the degree of increase in hardness of the sprayed layer is insufficient, and sufficient wear resistance is not achieved. I can't. Therefore, the proportion of TiC powder was set within the range of 10 to 50%.

Note that the metals used for the TiC-metal composite particle powder include:
It is desirable to use a material that has good wettability with TiC and high heat resistance, and Ni1CO1Ni-Cr
Alloys etc. are optimal. In addition, as for the composite form of TiC-metal composite particles, at least a part of the TiC particles are Ni.
, Co, etc., but in order to prevent sublimation and dispersion of TiC during thermal spraying as much as possible, T
It is desirable that the entire iC particle be covered with a metal such as Ni or Qo, that is, a particle coated with a metal such as Ni or Go. Further, the specific means for producing such composite particles is arbitrary;
For example, molten metal such as Ni or co is brought into direct contact with the surface of heated TiC particles to form a composite, or
C powder and metal powder such as Ni or CO may be mixed and granulated, and TiC particles and metal may be mechanically compressed, or they may be joined and integrated using an appropriate binder substance.
It is also possible to apply a plating method or the like to the roughness. Roughly speaking, the composition ratio of TiC and metal in the TiC-metal composite powder is not particularly limited, but is usually 228 to 8 by weight.
It is desirable that it be within the range of about 2. If the proportion of TiC in the composite powder particles is less than this, TiC in the sprayed layer
If the amount is too small, there is a risk that sufficient wear resistance cannot be obtained, and on the other hand, it is often difficult in actual operation to create composite powder particles with a smaller proportion of metal.

The thermal spraying method of the present invention may be applied directly onto a base material made of aluminum alloy or cast iron, but usually a base thermal spray layer is applied on the base material in advance, as shown in the examples of corrosion. For example, Ni-A1 alloy, Ni-Cr alloy, N1-Cr
It is desirable to form a base thermal spray layer made of a Ni-based alloy such as -A1 alloy or N1-Cr-A1-Y alloy, and then apply the thermal spraying method of the present invention thereon.

EXAMPLES Below, examples in which thermal spraying was carried out according to the method of the present invention and comparative examples outside the scope of the present invention will be described.

As a base material, width 6.35#, length 15.7711111
A test piece for an abrasion test made of JIS Fe12 with a height of 10.0 cm was prepared, and after cleaning the surface of the base material with acetone as a solvent, it was subjected to shot blasting to form irregularities on the surface. . Thereafter, an undercoat layer made of Ni-4.5 wt % A1 alloy was formed with a thickness of O.im using a plasma melting 9A apparatus.

On the other hand, Ti with a particle size of 10 to 50 IJIn is used as a thermal spray material.
C powder and TiC-50wt%CO with a particle size of 10 to 50
A composite powder consisting of the following was prepared, and these were mixed at various blending ratios as shown in blending conditions A to K in Table 1. Note that here, the TiC-50wt%CO composite powder is Ti
C particles whose surfaces were almost entirely coated with Go were used.

Each mixed powder under the above blending condition A- was thermally sprayed onto the undercoat layer using a plasma spraying device. Specifically, using Ar-H2 mixed gas, Ar flow 1401/
mm, H2 flow rate 10 l/n++ns current value 40
Thermal spraying was carried out at 0 A, and the spraying thickness was 300 mm.

Table 1 also shows the results of examining the hardness of the sprayed layer sprayed with the mixed powder under each compounding condition A-. As one of the comparative examples, a sintered TiC body obtained by a normal powder metallurgy method was used.
The hardness results are shown in Table 1 as symbols.

Table 1 and Fig. 1 schematically show the cross-sectional state of the thermal sprayed layer obtained under the conditions of the embodiment of this invention with compounding conditions C-G. Comparative example (
Figure 3 schematically shows the cross-sectional state of the sprayed layer under condition B, where the proportion of TiC powder not blended is too low (conventional method) or the proportion of TiC powder not blended is too low. In FIGS. 1 to 3, 1 is a base material, 2 is an undercoat layer, and 3 is a ceramic spray layer which is the object of the present invention. The symbol 4 in the sprayed layer 3 is a TiC phase (Ti
(including both those derived from C powder and those derived from T i C-Go composite powder), 5 indicates a CO phase (metallic phase). Furthermore, 6 indicates a hole.

As shown in Table 1, the blending ratio of TiC powder is 0 to 30.
% (symbols A-E), the hardness of the sprayed layer increases as the amount of TiC powder not mixed increases, but if the blending ratio of TiC powder increases beyond that (symbol F-K>), the hardness of the sprayed layer increases. The hardness of the sprayed layer decreases, especially when the proportion of TiC powder not added exceeds 50%, the hardness of the sprayed layer decreases rapidly.
If TiC powder is excessive, Ti that is not wrapped in metal
As the C particles increase, the TiC particles sublimate or decompose, and the resulting portions form pores 6 in the sprayed layer 3, as shown in FIG.
It is thought that the particles remain inside, making the structure brittle and decreasing its hardness.

Next, the wear resistance of the test piece and the sintered TiC shown in the symbol, which were thermally sprayed under each of the conditions A to K above, was evaluated using an LFW friction and wear tester. 5 as a mating material
An O3-2 hardened ring (hardness: Hv 720) was used, and the evaluation conditions were a mating ring rotation speed of 200 r times, a pressing load of 150 to 9, and oil bath lubrication.

The results are shown in FIG. The amount of wear was measured by the depth of wear on the sprayed surface of the test piece.

As is clear from Figure 4, the blending ratio of TiC powder is 1
In the case of 0 to 50% (C to G), wear resistance comparable to that of TiC sintered material (symbol L) was obtained. This is because, as shown in Figure 1, the TiC phase 4 surrounded by the metal (CO) phase 5 is densely dispersed throughout the entire surface including the surface, so although the overall hardness is not as high as that of TiC sintered material, This is thought to be due to the fact that the TiC's inherent good wear resistance was able to be demonstrated in the dispersed particles.

On the other hand, in A, which did not contain TiC powder, and B, in which the TIC content was less than 10%, the TiC content was low, and as shown in Figure 2, the degree of TiC dispersion was also low, so the wear resistance was poor. It wasn't enough.

In addition, when the blending ratio of TiC powder exceeds 50% (H-
K), as already explained with reference to FIG.
increased, the overall hardness decreased, the structure itself became brittle, and wear resistance deteriorated.

Effects of the Invention According to the method of the present invention, TiC powder is used as a thermal spraying material when forming a ceramic thermal spray layer using TiC, which has excellent properties such as wear resistance and heat resistance, but easily sublimes and decomposes during thermal spraying. Using a mixed powder of TiC-metal composite powder and TiC-metal composite powder, Ti
Ti is coated by thermal spraying to envelop C powder particles.
Sublimation and decomposition of C can be prevented, and by using both TIC powder and TiC-metal composite powder, the amount of TiC dispersed in the sprayed layer can be increased.
Thereby, it is possible to obtain a thermal sprayed layer that fully exhibits the original function of TiC and has excellent wear resistance.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing a sprayed layer obtained by an example of the present invention, and FIGS. 2 and 3 are schematic longitudinal cross-sectional views showing a thermal sprayed layer obtained by a comparative example, respectively. Fourth
The figure is a graph showing the relationship between the amount of TiC powder not added and the wear resistance of the sprayed layer, and FIG. 5 is a schematic vertical cross-sectional view showing an example of the sprayed layer obtained by the conventional method. 1... Base material, 2... Undercoat layer, 3...
・Thermal spray layer, 4... TiC phase, 5... Metal phase (C
o phase).

Claims (2)

[Claims] (1) Prepare a powder made of composite particles in which TiC and metal are integrated into a composite in advance, and combine this composite particle powder with TiC
1. A thermal spraying method for wear-resistant ceramics, which comprises mixing TiC powder so that TiC powder accounts for 10 to 50 wt%, and spraying the mixed powder onto a base material. (2) Co, Ni, Ni as metals in the composite particles
2. The thermal spraying method for wear-resistant ceramics according to claim 1, wherein one or more selected from -Cr alloys are used.