JP3370800B2 - Manufacturing method of composite material - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a composite material composed of ceramic powder and metal powder, the surface of which is rich in ceramics and the inside of which is rich in metal.

[0002]

2. Description of the Related Art For example, ceramics are widely used as materials for various machine parts because of their excellent hardness and heat resistance. However, this ceramic has a drawback that it is generally inferior in toughness, and therefore, a ceramic composite body (hereinafter referred to as a composite material) in which a ceramic and a metal are composited is recently adopted.

In this case, if the amount of ceramics is increased in order to improve the wear resistance of the composite material, the hardness increases, but the toughness decreases and the strength decreases. Therefore, a mixed powder of metal and ceramics having various different composition ratios is stacked stepwise and the mixed powder is sintered (hereinafter referred to as Conventional Example 1), a clad (adhesion), and a fitting. Or by shrink fitting (hereinafter referred to as Conventional Example 2
Is commonly used.

[0004]

However, in the above-mentioned conventional example 1, since the firing temperatures of the metal and the ceramics are largely different, the ceramics do not become densified on the basis of the firing temperature of the metal, while the ceramics of the ceramics are not densified. If the firing temperature is used as a reference, the shape cannot be maintained beyond the melting point of the metal. Moreover, since the densification rate of metal and ceramics and the shrinkage due to composition differ depending on the temperature, in addition to deformation,
It has been pointed out that a crack may occur.

Further, in the above-mentioned conventional example 2, since there is an interface between metal and ceramics, heat conduction, stress elastic waves, etc. are concentrated at this interface, and there is a problem that thermal stress or stress concentration occurs. .

The present invention solves this kind of problem, and by changing its physical properties in the depth direction, it is possible to produce a composite material having excellent surface hardness, high toughness and no interface. The purpose is to provide a method.

[0007]

In order to solve the above-mentioned problems, according to the present invention, a molded body is molded from a mixed powder of ceramic powder and metal powder, and the molded body is calcined to obtain a calcined body. After that, a method of manufacturing a composite material, in which a solution of a metal salt is impregnated in the pre-baked body and then the main baking is performed, wherein the metal salt solution is Fe, Ni, Co and VII of Group VIII of the periodic table.
It is characterized in that it is a solution containing a ceramic particle growth material which is at least one selected from Mn of group A, Cr of group VIA, and an organic metal salt or an alloy thereof.

[0008]

In the method of manufacturing a composite material according to the present invention, a mixed powder of metal and ceramics is obtained at a predetermined composite ratio, and a molded body molded with this mixed powder is pre-baked. Next, a metal that promotes grain growth of ceramic particles (hereinafter referred to as grain growth promoting material) is introduced into the pre-baked body in a form dispersed in an aqueous solution or an organic solvent, and then subjected to a main baking treatment. . During this main calcination, volume diffusion of the metal and grain growth of the ceramic particles are caused with an increase in the calcination temperature, so that a composite material having a ceramic-rich surface side and a metal-rich gradient function inside can be obtained. it can.

[0009]

The method for producing a composite material according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a flow chart showing a processing procedure of the method of the present invention, which will be schematically described. First, a mixed powder of metal and ceramics prepared in a predetermined composite ratio is obtained (step S1), and a molded body is molded with this mixed powder (step S2). This molded body has a temperature of 800 ° C. after the molding auxiliary material added at the time of molding is degreased.
A calcination process is performed by heating at 1000 ° C. for about 15 to 60 minutes (step S3).

At this time, the particles of the metal powder are maintained in a state in which a contact between the powder particles is volume-diffused and adhered, that is, a so-called neck is formed. If the formation of this neck proceeds too much, the continuous pores and voids will be blocked, and impregnation with the metal salt solution or the organic metal solution in the subsequent step will not be effectively performed. In addition, it is necessary that the pores be connected three-dimensionally when the neck is generated. Therefore, the powder forming load cannot be increased to the plastic deformation region of the metal, and the forming load is 1
It is set to 00 MPa to 300 MPa.

After the calcination, the grain growth promoting material is introduced into the calcination body (step S4). This introduction is most effective when the grain growth promoting material is used in the minimum unit, and is introduced in the form of ions or single molecules. Specifically, the grain growth promoting material is
The pores of the calcined body are impregnated in the form of being dispersed in an aqueous solution or an organic solvent. Although it is possible to introduce the grain growth promoting material in the step of mixing the raw material powders, it is not preferable because there is an influence during degreasing and firing and strict control such as change of firing pattern is required. On the other hand, in the impregnation of the pre-baked body, since the neck of the metal particles is generated, the volume diffusion during the baking is smooth and the influence on the sintering is small.

Next, after the solvent is dried and removed (step S5), a main baking process is performed (step S6). During this main calcination process, volume diffusion of metal and grain growth of ceramic particles are caused as the calcination temperature rises. Grain growth of ceramic particles is an endothermic reaction, and grain growth starts on the surface of the pre-fired body where the temperature rises fastest. When an endothermic reaction occurs on the surface, heat is taken away there, resulting in a thermal gradient.

The grain growth promoting material acts as a kind of catalyst and is slightly incorporated into the grains during grain growth, but most of them move further to the inside and accumulate in the portion where grain growth is still small. As described above, the growth degree of grain growth is determined by heat exchange, and the thickness of the grain growth portion and its gradient can be controlled by the heating rate and the holding time.

Further, in the composition of the composite material, the ceramic component becomes approximately 100% at the portion where the grain growth on the surface greatly progresses, while the initial composite component remains or becomes metal-rich at the inner deep portion. Therefore, it is possible to obtain a composite material having a gradient function in which the surface side is ceramics rich and the inside is metal rich.

Further, a grain growth promoting material and a material for forming a ceramics film are selected and impregnated, or the surface layer is covered with a ceramics film and then fired to form a ceramics film having a diffusion layer in the grain growth part and the coating layer. It can be molded. <Example 1> 78 wt% WC (tungsten carbide) powder having an average particle size of 2 μm, 2 wt% TaC (tantalum carbide) powder having an average particle size of 1 μm, and an average particle size of 1 μm
20% by weight of the metal Co (cobalt) powder of 1 was sufficiently mixed with ethyl alcohol as a dispersion medium. After this mixing, granulation was performed to about 100 μm, and a molded body of 22 × 5 × 80 mm was molded at a molding pressure of 150 MPa. And it hold | maintained in vacuum at 450 degreeC for 30 minutes, and also at 650 degreeC for 30 minutes, and after that, it heated up to 1050 degreeC and hold | maintained at that temperature for 60 minutes, and obtained the calcination body.

Next, each of the calcined bodies is dipped in a 10% aqueous solution, a 20% aqueous solution, a 30% aqueous solution and a saturated solution of nickel nitrate while being subjected to ultrasonic vibration,
A nickel nitrate solution was impregnated into these calcined bodies.
The applied ultrasonic vibration was 16 MHz, and the immersion time was 10 minutes.

These pre-baked bodies were dried at 80 ° C. for 12 hours and then dried at a heating rate of 10 ° C./min for 1 hour.
The temperature is raised to 000 ℃ and held for 30 minutes, then 5 ℃
The temperature was raised to 1360 ° C. at a heating rate of / min and held in vacuum for 90 minutes. As a result, a fired body (composite material) was obtained.

The surface of the fired body is mirror-polished and cut at the center to be mirror-finished to obtain Hv.
Changes in hardness and average particle size were detected by electron microscopy. The results are shown in FIGS. 2 and 3. Also, the main fired body is cut into a thickness of 1 mm, and the span is 30 mm.
The bending strength was measured with. At that time, a large number of test pieces were prepared so that a change in strength due to a change in distance from the surface could be traced. The result is shown in FIG. Further, FIG. 5 shows a chemical analysis of the test piece taken out in the bending strength test, and shows changes in the amounts of metal and ceramics corresponding to changes in the distance from the surface. The change in toughness value is shown corresponding to the change in distance from the surface.

As described above, according to the first embodiment, the physical properties such as hardness and strength of the main fired body are inclined in the depth direction of the main fired body, and the cause of the change is grain growth. It was found to be based on. Further, from FIG. 5, it was found that the amount of metal gradually changed inward as the ceramic particles grew. Furthermore, among the obtained physical property values, the surface hardness is as high as Hv 2500, which is comparable to that of PVD coating or CVD coating, and the strength is 4.5 GPa, which is equivalent to the ultrafine particle superhard top grade product,
The fracture toughness value as toughness data was equivalent to that of the FC material. Therefore, due to the grain growth of the ceramic particles, high values of hardness, strength, and toughness that could not be achieved by conventional materials were obtained. Example 2 The metal and ceramic particles constituting the composite material were prepared so as to have the composition shown in Table 1, and these were sufficiently mixed, and then a 22 × 5 × 80 mm test piece was molded. The test piece was calcined in a temperature range of 900 ° C. to 1100 ° C. to obtain a calcined body.
As shown in Experimental Examples 1 to 24, various metal salts and organic metals are impregnated as a grain growth promoting material, and after being dried, 1360
Main-baking treatment was performed in the temperature range of ℃ to 1450 ℃ to obtain the main-baked body. This main firing process is performed in a nitrogen atmosphere at 1 ba
It was performed under a pressure of 1 or a reduced pressure of 0.1 to 1 Torr.

[0021]

[Table 1]

Therefore, Comparative Examples A to F were prepared in which the composite material examples were directly fired without being impregnated with the grain growth promoting material. Next, each of the main fired bodies was subjected to mirror polishing, and then the Hv hardness was measured at a position displaced from the surface by a predetermined distance. In addition, the thickness from the main fired body is 1 m
A 4 × 50 mm test piece for bending test was cut at m, and the bending strength was measured at a span of 30 mm. These results are shown in Table 2.
Is shown in.

[0023]

[Table 2]

Further, in the central cross section of the test piece, the change in the size of the constituent particles of the composite material was measured from the surface by an electron microscope, and the change in the amount of metal corresponding to the change in the distance from the surface was detected. . These results are shown in Table 3 and Table 4.
Is shown in.

[0025]

[Table 3]

[0026]

[Table 4]

From these results, it was found that in the second example, the physical property values changed from the surface of the main body to the inside. This was due to grain growth, and the chemical composition also changed with this grain growth (see Table 3). As a result, the metal on the surface side moves inward as the ceramic particles that are the constituents of the composite material grow,
It was confirmed that the chemical composition also changed gradually.

[0028]

As described above, according to the method of manufacturing a composite material of the present invention, the following effects can be obtained.

After the grain growth promoting material is introduced into the pre-baked body in a form of being dispersed in an aqueous solution or an organic solvent, the main-baking treatment is performed. Therefore, during the main-baking treatment, as the firing temperature increases, Volume diffusion of metal and grain growth of ceramic particles are caused. Therefore, it is possible to obtain a composite material having a gradient function in which the surface side is ceramic-rich and the inside is metal-rich, and the abrasion resistance, slidability, and heat resistance of the surface layer of the composite material are improved by simple and inexpensive work. In addition, it is possible to increase the strength of the inside of the composite material.

[Brief description of drawings]

FIG. 1 is a flowchart for explaining a manufacturing method according to the present invention.

FIG. 2 is a diagram showing a relationship between a change in distance from the surface and a change in hardness.

FIG. 3 is a diagram showing a relationship between a change in distance from the surface and a change in particle diameter.

FIG. 4 is a diagram showing a relationship between a distance change from a surface and a bending strength change.

FIG. 5 is a diagram showing a relationship between a distance change from the surface and a metal amount change.

FIG. 6 is a diagram showing a relationship between a change in distance from the surface and a change in fracture toughness value.

Front page continued (72) Inventor Kazuhito Hiraga 1-10-1 Shin-Sayama, Sayama City, Saitama Honda Engineering Co., Ltd. (58) Fields investigated (Int.Cl. ⁷ , DB name) B22F 7/06

Claims (4)

(57) [Claims] 1. A molded body is molded from a mixed powder of ceramic powder and metal powder, and the molded body is calcined to obtain a calcined body, and the calcined body is impregnated with a solution of a metal salt. A method of manufacturing a composite material comprising firing, wherein the metal salt solution is Fe, Ni of Group VIII of the periodic table,
A method for producing a composite material, which is a solution containing a ceramic grain growth material which is at least one selected from Co, MIA in the VIIA group, Cr in the VIA group, and an organometallic salt, or an alloy thereof. 2. The method for producing a composite material according to claim 1, wherein the salt of the metal salt solution is a nitrate salt, an acetate salt or a chloride salt. 3. The manufacturing method according to claim 1, wherein the organic metal salt is Fe, Ni, Co and VIIA of Group VIII.
A method for producing a composite material, comprising at least one selected from Mn of group I and Cr of group VIA or an alloy thereof. 4. The method for manufacturing a composite material according to claim 1, wherein the pre-baked body is in a state where particles are adhered to each other.