JPS61296972A - Formation of ceramic particle dispersed composite metallic layer - Google Patents

Abstract

PURPOSE:To improve the quality characteristics of a composite layer and to reduce the cost thereof by mixing ceramic powder and metallic powder and disposing the mixture on the surface of a metallic material then heating and melting the powder mixture by a high-density energy source. CONSTITUTION:The ceramic powder having 0.3-500mu average grain size and the metallic powder having <=300mu average grain size are uniformly mixed. An aq. soln. of a PVA or the like is poured as a binder into the powder mixture composed thereof to form a paste. The paste is disposed between guides of a metallic material piece 1 and is dried to form a powder mixture layer 6. The powder mixture layer 6 is melted by a TIG arc 7. etc. to form a composite alloy layer 8 dispersed with the ceramic particles on the material 1. The ceramic particles are uniformly dispersed by the above-mentioned method, by which the strength and corrosion resistance of the composite layer are improved and the cost thereof is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to surface treatment of metal materials, and more particularly to a method for forming a ceramic particle-dispersed metal composite layer on the surface of a metal material.

Conventional technology As a means of improving the wear resistance, heat resistance, corrosion resistance, etc. of metal materials such as steel, it is possible to incorporate ceramic particles into metal materials, which themselves have high strength and high hardness and have excellent heat resistance and corrosion resistance. It is known that it is effective to disperse ceramic particles into metal composite materials or composite layers.

Thus, as a method for dispersing ceramic particles in a metal material, a supersaturated solid solution is formed by performing solution treatment on a metal material containing a solid solution-forming element such as a metal carbide, and the supersaturated solid solution is dispersed in a predetermined manner. A precipitation hardening method in which a solid solution is aged and precipitated by holding it at a temperature for a certain period of time, and a metal material containing a metal element that is more reactive with oxygen than the base metal is maintained at a specified temperature for a certain period of time in an oxidizing atmosphere. An internal oxidation method in which the element is oxidized inside the metal material by diffusing oxygen from the surface of the metal material to the inside thereof, mixing the ceramic powder to be dispersed and the base metal powder, A powder metallurgy method (sintering method) in which the mixed powder is compression-molded and the compression-molded body is heated to a high temperature, the ceramic powder to be dispersed in the molten base metal is added and stirred, and the thus obtained Compocasting methods for casting mixed molten metal have been known for some time.

Problems to be Solved by the Invention In the precipitation hardening method described above, it is possible to disperse extremely fine dispersed particles in the base metal, and a composite material with excellent adhesion between the dispersed particles and the base metal can be created. However, it is difficult to properly control the volume fraction, size, shape, etc. of the dispersed particles, and the aging treatment requires heating and maintaining the metal material at a predetermined temperature for a long time. First, it is difficult to form a ceramic particle-dispersed metal composite layer inexpensively and efficiently because it is necessary to process the entire metal material. It is difficult to manufacture metal materials.

In addition, in the internal oxidation method, the metal material to be treated must contain a gold layer element that is more reactive with oxygen than the base metal, and the metal material is heated to a high temperature near its melting point. Since heating must be maintained for a long time and the rate of oxidation of the metal element is limited by the rate of oxygen diffusion into the metal material, a metal composite layer with oxide-based ceramic particles dispersed on the surface of the metal material is used. It is difficult to form this efficiently and inexpensively. Furthermore, in this method, it is impossible to disperse ceramic particles other than 1ift compound-based ceramic particles into the base metal, and it is also difficult to appropriately control the volume fraction, size, shape, etc. of oxide-based ceramic particles. is difficult.

Furthermore, in the powder metallurgy method, the volume fraction, size, shape, etc. of ceramic particles can be controlled relatively easily;
Ceramic particle dispersed gold a only on a specific surface area of the metal material
It is very difficult to form an S composite layer, and therefore it is difficult to easily and inexpensively form a ceramic particle-dispersed metal composite layer on a specific surface portion of a metal material. Furthermore, it is extremely difficult to form a ceramic particle-dispersed metal composite layer with substantially zero porosity or a reramic particle-dispersed metal composite layer with excellent adhesion between the ceramic particles and the base metal.

Furthermore, in the composite casting method, although it is possible to easily produce a casting made of a ceramic particle-dispersed metal composite material, it is very difficult to form a ceramic particle-dispersed metal composite layer only on a specific surface area of the metal material. It is difficult to form a composite layer in which ceramic particles are uniformly dispersed, and it is very difficult to appropriately control the volume fraction of ceramic particles in the composite layer.

In view of the above-mentioned problems in the conventional method of dispersing ceramic particles in metal materials, the present invention has been developed to uniformly disperse ceramic particles of any type, such as oxide, nitride, or carbide, at a desired volume fraction. The object of the present invention is to provide a method that can easily, inexpensively, and efficiently form a metal composite layer containing dispersed ceramic particles on a desired surface of a metal material.

Means for Solving the Problems According to the present invention, a ceramic powder and a metal powder are mixed, the mixed powder is placed on the surface of a metal material, and the mixed powder is applied to a high-density energy source. A method for forming a ceramic particle-dispersed metal composite layer is achieved by heating the metal powder at a temperature to melt the metal powder.

Functions and Effects of the Invention According to the method of the present invention, a mixed powder of ceramic powder and metal powder is placed on the surface of a metal material, and the mixed powder is locally heated to a high temperature with a high-density energy source. Since the metal powder is melted (including a semi-molten state), by using ceramic powder of a desired shape and uniformly mixing the ceramic powder and metal powder at a predetermined ratio, it is possible to substantially form the desired shape. A composite layer in which ceramic particles are uniformly dispersed at a desired volume ratio can be easily and efficiently formed on a specific surface of a metal material. Because it is melted,
A composite layer with excellent integrity with the metal material can be formed.

Further, according to the method of the present invention, the heat input to the mixed powder etc. is much smaller and in a shorter time than in the conventional method where the entire metal material is heated to a high temperature for a long time. It is localized and can form a ceramic particle-dispersed metal composite layer only on any specific surface of the metal material, rather than the ceramic particles being dispersed throughout the metal material as in powder metallurgy. The composite layer can be formed at low cost only on the desired surface of the metal material without substantially causing adverse thermal effects on the parts.

Furthermore, according to the method of the present invention, the ceramic particles dispersed as in the case of the internal oxidation method are not limited to oxide-based ceramic particles, and the metal powder mixed with the ceramic powder (two or more metal powders) By appropriately selecting the materials (including mixtures), in addition to improving properties such as wear resistance by dispersing ceramic particles, it is possible to improve properties such as corrosion resistance by changing the composition of the matrix metal of the composite layer.

Furthermore, according to the method of the present invention, by changing the ratio of ceramic powder to metal powder in the mixed powder disposed on the surface of the metal material in the thickness direction, for example, the parts of the composite layer closer to the metal material are It is possible to form a composite layer in which the volume fraction of ceramic particles changes in the thickness direction, such as a composite layer in which the volume fraction of ceramic particles increases toward the surface. It can also be changed continuously in the horizontal direction.

According to one detailed feature of the method of the invention, the metal powder melted in the high-density energy source is rapidly cooled primarily by heat absorption by the metal material. According to this method, there is no need for a special cooling device for cooling the molten metal powder, and since the surface of the molten metal powder and the metal material heated to a high temperature is rapidly cooled, The crystals of the matrix metal are fine, so a composite layer with excellent strength etc. can be formed.

According to another detailed feature of the method of the invention, heating the mixed powder with a high-density energy source to melt the metal powder takes place in an inert atmosphere. According to this method, it is possible to avoid problems such as oxidation of the metal powder and oxidation of the matrix metal of the composite layer. In this case, the inert atmosphere may be created using flux as in the case of welding, but from the viewpoint of reliability, avoidance of slag entrainment, and workability, an inert gas atmosphere such as argon or helium or a vacuum atmosphere may be used. It is preferable that there be.

Further, the high-density energy source used in the method of the present invention may be a laser, a TIG arc, or an electron beam, but the laser can also be applied when the electrical resistance of metal powder or metal material is relatively high. TIG arc and electron beam are superior to other high-density energy sources in that the size of the heating range for mixed powder can be adjusted relatively easily by adjusting the focus. It is superior to lasers in that metal and ceramic powders are stirred by electromagnetic stirring. Furthermore, while the atmosphere for electron beams generally must be a vacuum atmosphere, the atmosphere for lasers and TIG arcs may be inert gas atmospheres, so the equipment and work efficiency necessary to create and maintain the specified atmosphere are not sufficient. From this point of view, lasers and TIG arcs are preferable, but compared to electron beams, they have a very small heating fR range and a large melt penetration depth, so if such characteristics are required, other high-density energy sources may be used. Yet another detailed feature of the method of the present invention.

According to the above, a laser, an I'IG arc, or an electron beam can be appropriately used as a high-density energy source depending on the type of ceramic powder or metal powder, the shape, area, thickness, etc. of the composite layer to be formed.

In addition, the ceramic powder in the method of the present invention is 5tOt,
Oxide-based ceramic powders such as Al 203 , MtJ O, Zr 02 (7), S'! JNa, T i
Nitride ceramic powder such as N, Ti C, Si
C, W.C.

It may be any type of ceramic powder such as carbide ceramic powder such as MOC or a mixed powder thereof,
The metal powder may be a single type of metal powder or a mixed powder of multiple types of metal powder, and may also be a metal powder with a composition different from that of the metal material or a metal powder with substantially the same composition. However, in order to form a composite layer in which ceramic particles are uniformly dispersed, it is preferable that the ceramic powder and the metal powder are substantially uniformly alpha-combined.

According to the results of experimental research conducted by the inventors of the present application,
In order to easily melt the metal powder and to prevent the formation of neutralization pores in the composite layer, the average particle size of the metal powder should be 3.
It is preferably 00 μ or less, particularly 100 μ or less,
In order to form a uniform mixed powder of ceramic powder and metal powder, thereby forming a composite layer in which ceramic particles are substantially uniformly dispersed, the average particle size of the ceramic powder is 0.3 to 500μ, In particular, it is preferably 0.4 to 200μ. However, the average particle size of ceramic powder is 10μ
When the ceramic powder is small as described below, it is completely melted by heating and becomes granulated by agglomerating in the matrix metal.

Further, disposing the mixed powder of ceramic powder and metal powder on the surface of the metal material may be carried out by simply disposing the mixed powder in advance in a layer on the surface of the metal material. In the case of laser or electron beam, it may be carried out by continuously feeding the mixed powder to the surface of the metal material at a position in front of the high-density energy source in the scanning direction, but scattering of the mixed powder may be carried out. In order to prevent this and improve the yield, it is possible to place the compacted powder of the mixed powder on top of the metal material, or to form grooves on the surface of the metal material and compact the mixed powder in the grooves. Molding or adding P to mixed powder
A paste is formed by adding a binder such as an aqueous solution of , V, A, (polyvinyl alcohol) or a mixture of cellulose and glycerin, and the paste is attached to the surface of the metal material by spatula coating or tube method. If the thickness of the composite layer to be formed is small, the mixed powder is dispersed in a solvent such as a solvent in which acrylic resin is dissolved in thinner to form a slurry, and the slurry is brushed off. Coating by methods such as spraying, dipping, etc. may be performed by adhering to the surface of the metal material by a method. However, when a paste or slurry is formed, the surface of the mixed powder layer formed by drying the paste or slurry may be oxidized or pores may be generated on the surface of the mixed powder layer. Preferably, the material is sufficiently dried in a temperature range and atmosphere free of moisture, and is heated with a high-density energy source in a substantially moisture-free state.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will be explained in detail below by way of example embodiments with reference to the accompanying figures.

Example 1 Alumina powder with an average particle size of 15 μm and nickel powder with an average particle size of 80 μm (purity: 99.9%) are uniformly mixed. ! ! A mixed powder was formed with a ratio of 1:4. A 5% aqueous solution of polyvinyl alcohol as a binder was then injected into the mixed powder to form a paste that was more viscous than water and less viscous than clay.

Then, as shown in FIG.
Tool steel with +n+ dimensions (JIS standard 5KD61)
Prepare a test piece 1 made of aluminum alloy, and on one of its 70×40nv surfaces, two guides 2 and 3 with a thickness of 0°811IIll are arranged in parallel along the longitudinal direction with a distance of 5111111 mm from each other. A width of 5 nu++ is applied to the center of said surface of the specimen along its longitudinal direction by spatula filling paste 4 between the guides.

The paste was arranged in a layer with a thickness of 0.8 ml. Next, although not shown in the figure, the test piece was placed in a drying oven for 100 minutes.
The paste was thoroughly dried by holding at 0.5 μm for 0.5μ. The porosity of the mixed powder layer thus obtained was approximately 45.
%Met.

Next, as shown in FIG. 2, argon as a shielding gas is emitted from the tip of the TIG torch 5, thereby shielding the molten part on the test piece, and applying TIG from one end of the mixed powder layer 6 to the other. By scanning the torch 5 for one bus, the mixed powder layer is locally heated by the TIG oven 7 under the conditions shown in Table 1 below to melt the nickel powder, and as a result, the nickel powder is melted as shown in FIG. As shown, a composite m8 consisting of a nickel alloy in which alumina particles were dispersed was formed. In this case, a part of the alumina powder and the part directly below the mixed powder layer of the test piece are also partially melted, and the thus generated molten metal, heated alumina powder, and the surface of the test piece are mainly melted by the main part of the test piece. It was rapidly cooled by absorbing heat.

Table 1 Current: 120△ Voltage: 20V Polarity: DC rod positive electrode: Tungsten scanning speed + 2.51111I/Sec Arc length:
6 mm Argon flow m: 50 l/l1lin The width of the composite layer formed as described above was 6.8 mm and the maximum thickness was 1.8 mm. Furthermore, when we observed the cross section of the longitudinal center of the test piece, we found that there was a heat-affected zone 1o between the composite layer 8 and the base metal 9 of the test piece, as schematically shown in FIG. Although it existed, its width was 1.5 to 2. Q
It was about mm. Also, the alumina particles 110 in the composite layer
The volume fraction is approximately 9% and is substantially uniform over the entire composite layer, and the integration between the alumina particles and the nickel alloy 12 as the matrix metal and the composite layer and the test piece are also good. was recognized. Furthermore, the average particle size of the alumina particles was 5.5μ.

FIG. 5 is an optical micrograph showing the metal structure at the center of the longitudinal cross section of the composite layer 8 at 400 times magnification. In the figure, the white part is the nickel alloy part as the matrix metal, and the black dotted part is the alumina particles. From FIG. 5, it can be seen that fine alumina particles of substantially uniform size are uniformly dispersed in the matrix metal, and defects such as pores are not generated at all.

Example 2 Aluminum nitride powder with an average particle size of 10μ and an average particle size of 80μ
nickel powder (1 degree 99.9%) was mixed uniformly, thereby forming a mixed powder in which the weight ratio of these powders was 1:4. Then, by injecting a 5% aqueous solution of polyvinyl alcohol as a binder into the mixed powder,
A paste of substantially the same viscosity as the paste of Example 1 was formed.

Next, a test piece with the same dimensions and the same material as the test piece used in Example 1 was prepared, and in the same manner as in Example 1, a test piece was placed in the center of one of the 70 x 40111 m surfaces in the longitudinal direction. By arranging the paste in a layer with a width of 5 mm + and a thickness of 0.8 mm along the pores, and drying the paste sufficiently under the same conditions as in Example 1, the pores are formed as shown in Fig. 6. A mixed powder layer 13 having a ratio of about 45% was formed on the test piece 14.

Next, as shown in FIG.
A vacuum atmosphere was established by reducing the pressure to 0 Torr. Next, an electron beam 18 emitted from the electron beam gun 17 is irradiated onto one end of the mixed powder layer 13, and while the electron beam gun 17 is reciprocated in the width direction of the mixed powder layer, the test piece 14 is placed on the mounting table 16. By feeding the nickel powder in the longitudinal direction, the mixed powder is locally heated by the electron beam 18 under the conditions shown in Table 2 below to melt the nickel powder, which is shown in FIG. In this way, a composite layer 19 made of a two-gallon alloy in which aluminum nitride particles were dispersed was formed. In this case, part of the aluminum nitride powder and the part directly below the mixed powder layer of the test piece are also partially melted, and the thus generated molten metal, heated aluminum nitride powder, and the surface part of the test piece mainly melt into the main part of the test piece. It was rapidly cooled by absorbing heat from the surrounding area.

Table 2): 50 kV x 40 mA Defocus: 10 mm Test piece feeding speed: 5111R/Sec Reciprocating speed of electron beam: 6000 av/sea The width of the composite layer formed as described above was 5.2 mm. The maximum thickness was 2.6111II. In addition, when the cross section of the central part in the longitudinal direction of the test piece was measured by is 0.5 to 0.811I1
It's about 1 and it's 5. In addition, the volume fraction of aluminum nitride particles in the composite layer is about 5%, which is substantially uniform throughout the composite layer, and the adhesion between the aluminum nitride particles and the nickel alloy as the matrix metal and the relationship between the composite layer and the specimen. It was also observed that the integrity was good. Furthermore, the average particle size of the aluminum nitride particles was 2.8μ.

FIG. 9 is an optical micrograph showing the metal structure at the center of the longitudinal cross-section of the composite layer 19 at 800 times magnification.

In the figure, the gray area is the nickel alloy as the matrix metal, and the white dotted area is the aluminum nitride particles.

From FIG. 9, it can be seen that fine aluminum nitride particles of substantially uniform size are uniformly dispersed in the matrix metal, and defects such as pores are not generated at all.

Example 3 Tungsten carbide powder with an average particle size of 5μ and an average particle size of 60μ
uniformly mixed with cobalt powder (purity 95.0%),
This formed a mixed powder in which the weight ratio of these powders was 1:1. A viscous paste similar to that in Example 1 was then formed by injecting a 5% aqueous solution of polyvinyl alcohol as a binder into the mixed powder.

Next, prepare a test piece with the same dimensions and the same material as the test piece used in Example 1, and in the same manner as in Example 1, place the long side of the test piece in the center of one of the 70 x 40 + on surfaces. The paste was arranged in layers of @51 layers, thickness Q, and 8 mm along the direction. Next, by sufficiently drying the paste under the same conditions as in Example 1, the 10th
As shown in the figure, a mixed powder layer 20 having a porosity of 40% was formed on a test piece 21.

Next, as shown in FIG. 11, helium as a shielding gas is emitted from the tip of the laser gun 22, thereby shielding the molten part on the test piece with helium, and spreading the mixed powder layer 20 from one end to the other. laser gun 22
By scanning one bus, the mixed powder layer is locally heated by the laser 23 under the conditions shown in Table 3 below to melt the cobalt powder, and as a result, as shown in FIG. 12, A composite layer 24 made of cobalt in which tungsten carbide particles were dispersed was formed. In this case, a part of the tungsten carbide powder and the part immediately below the mixed powder layer of the test iA piece also partially melted and sags, thus causing molten metal, heated tungsten carbide powder, and the surface of the test piece. The test piece was rapidly cooled by heat absorption mainly by the main part of the specimen.

Table 3 Power density: 240 W/llm2 Energy density: 180 J/mm2 Scanning speed: 240 mm/sec Helium flow ffi: 50 l/min The width of the composite layer formed as described above is 5.4 m + n, and the maximum thickness is It was 1.21. In addition, when we observed the cross section of the central part of the test piece, it was found that there was a heat affected zone between the composite layer and the base metal of the test piece, as in Example 1.
Its width was approximately 0.8 to 1.0 mm+. In addition, the volume fraction of tungsten carbide particles in the composite layer is approximately 25%, which is substantially uniform over the entire bonding layer, and the adhesion between the tungsten carbide particles and the cobalt alloy as the matrix metal and the relationship between the composite layer and the specimen. It was also observed that the integrity was good. Furthermore, the average particle size of tungsten carbide particles is 2
It was 0μ.

FIG. 13 is an optical micrograph showing the metal structure at the center of the longitudinal cross-section of the composite layer 24 at a magnification of 400 times. In the figure, the black to dark gray parts are cobalt alloy parts as the matrix metal, and the white dot-like or island-like parts are tungsten carbide particles. From FIG. 13, it can be seen that tungsten carbide particles of relatively fine and relatively uniform size are uniformly dispersed in the matrix metal, and defects such as pores are not generated at all.

It is assumed that the large island-shaped portions in FIG. 13 are relatively large lump-like tungsten carbide particles mixed in the tungsten carbide powder used to form the mixed powder.

Although the present invention has been described in detail with respect to specific embodiments above, the present invention is not limited to these embodiments, and various embodiments are possible within the scope of the present invention. will be clear to those skilled in the art.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing how to place the paste on the surface of the test piece, with parts of the paste and guide cut away. Figure 2 is a composite layer formed by melting the mixed powder layer on the test piece with a 1. Fig. 3 is a perspective view showing the composite layer formed on the test piece by the process shown in Fig. 2, and Fig. 4 is a longitudinal view of the test piece with the composite layer formed. Fig. 5 is an optical micrograph showing the metal structure of the central part of the cross section of a composite layer made of a nickel alloy in which alumina particles are dispersed at a magnification of 400 times. Figure 6 is a perspective view showing a test piece with a mixed powder layer formed on its surface, Figure 7 is an illustration showing the process of melting the mixed powder layer with an electron beam to form a composite layer, and Figure 8 is a A perspective view showing the composite layer formed by the process shown in the figure. Figure 9 is an optical micrograph showing the metal structure at the center of the cross section of the composite layer made of a nickel alloy in which aluminum nitride particles are dispersed, magnified at 800 times. , FIG. 10 is a perspective view showing a test piece with a mixed powder layer formed on its surface, and FIG. 11 shows a composite layer formed by melting the mixed powder layer using a rede. Illustrations showing the process,
Fig. 12 is a perspective view showing the composite layer formed by the process shown in Fig. 11, and Fig. 13 shows the metal structure in the center of the cross section of the composite layer made of cobalt alloy in which tungsten carbide particles are dispersed, magnified 400 times. This is an optical microscope photograph shown. 1... Test piece, 2.3... Guide, 4... Paste. 5... TIG torch, 6... Mixed powder layer, 7...
TIG arc, 8... composite layer, 9... base metal,
10... Heat shadow stomach area, 11... Alumina particles, 12.
...Nickel alloy, 13...Mixed powder layer, 14...
Test piece, 15... Vacuum container, 16... Mounting table, 17
...Electron beam gun. 18... Electron beam, 19... Composite layer, 20...
Mixed powder layer, 21...Test piece, 22...Laser gun, 23...Laser, 24...Composite layer Patent Applicant: Toyota Motor Corporation representative
Attorney Masatake Akashi Figure 1 Figure 3 Figure 4 Figure 5 (x 4001 Figure 6 Figure 7 Figure 9 Figure 11 Figure 13 t * 4Ut> )

Claims (6)

[Claims] (1) A ceramic particle-dispersed metal composite layer in which ceramic powder and metal powder are mixed, the mixed powder is placed on the surface of a metal material, and the mixed powder is heated with a high-density energy source to melt the metal powder. How to form. (2) In the method for forming a ceramic particle-dispersed metal composite layer according to claim 1, the molten metal powder is rapidly cooled mainly by heat absorption by the metal material. How to form a composite layer. (3) In the method for forming a ceramic particle-dispersed metal composite layer according to claim 1 or 2, the step of heating the mixed powder with a high-density energy source to melt the metal powder is not included. A method for forming a ceramic particle-dispersed metal composite layer, characterized in that it is carried out in an active atmosphere. (4) The method for forming a ceramic particle-dispersed metal composite layer according to any one of claims 1 to 3, wherein the high-density energy source is a laser. How to form layers. (5) The method for forming a ceramic particle-dispersed metal composite layer according to any one of claims 1 to 3, wherein the high-density energy source is a TIG arc. How to form a composite layer. (6) The method for forming a ceramic particle-dispersed metal composite layer according to any one of claims 1 to 3, wherein the high-density energy source is an electron beam. How to form a composite layer.