JPH0585273B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to surface treatment of metal materials, and more particularly to a method for forming a metal composite layer in which carbide-based ceramic particles are dispersed 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, ceramic particles, which themselves have high strength and hardness and have excellent heat resistance and corrosion resistance, are incorporated into metal materials. It is known to be effective to disperse and thereby form ceramic particle-dispersed 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 oxygen is diffused from the surface of the metal material to the inside thereof to oxidize the element inside the metal material, and the ceramic powder to be dispersed and the base metal powder are mixed, and the mixing A powder metallurgy method (sintering method) in which powder is compression molded and the compression molded body is heated to a high temperature, ceramic powder dispersed in a molten base metal is added and stirred, and the mixture thus obtained is Compocasting methods for casting 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 of the dispersed particles, and the aging treatment requires heating and maintaining the metal material at a predetermined temperature for a long period of time, resulting in damage to the entire metal material. It is difficult to form a ceramic particle-dispersed metal composite layer inexpensively and efficiently because of the need to process the ceramic particle-dispersed metal composite layer. is difficult. In addition, in the internal oxidation method, the metal material to be treated must contain a metal element that is more reactive with oxygen than the base metal, and the metal material must be kept at high temperatures near its melting point for a long time. 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 applied. It is difficult to form it efficiently and inexpensively. Furthermore, in this method, it is impossible to disperse carbide-based ceramic particles in the base metal, and it is also difficult to appropriately control the volume fraction of the ceramic particles. Furthermore, in the powder metallurgy method, although it is possible to control the volume fraction, size, shape, etc. of ceramic particles relatively easily, it is difficult to form a ceramic particle-dispersed metal composite layer only on a specific surface area of the metal material. 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 ceramic particle-dispersed metal composite layer with excellent adhesion between the ceramic particles and the base metal. Furthermore, in the composite cast method, although it is possible to easily produce a casting made of a ceramic particle-dispersed metal composite material, it is extremely 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 properly 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 a metal material, the present invention provides a ceramic particle-dispersed metal composite layer in which carbide-based ceramic particles are uniformly dispersed at a desired volume ratio. It is an object of the present invention to provide a method that can easily, inexpensively, and efficiently form a metal material on a desired surface of a metal material. Means for Solving the Problems According to the present invention, the above object is to mix a powder of a metal element highly reactive with carbon and a carbon powder, and to arrange the mixed powder on the surface of a metal material. This is achieved by a method of forming a metal composite layer in which carbide ceramic particles are dispersed, in which the mixed powder is heated and melted using a high-density energy source. Effects and Effects of the Invention According to the method of the present invention, a mixed powder of a metal element powder highly reactive with carbon and a carbon powder is placed on the surface of a metal material, and the mixed powder is locally localized with a high-density energy source. By heating the metal powder to a high temperature, the metal powder is melted (including in a semi-molten state), and the metal and carbon powder are activated, thereby carbonizing the metal and forming a metal carbide, that is, a carbide-based metal powder. Ceramic is formed in a dispersed state, so by uniformly mixing metal powder and carbonized powder at a predetermined ratio, a composite layer in which carbide-based ceramic particles are uniformly dispersed at a desired volume ratio can be created. It can be easily and efficiently formed on a specific surface of a metal material, and in this case, the surface of the metal material is partially melted together with the metal powder, so a composite layer with excellent integrity with the metal material can be created. can be formed. Furthermore, according to the method of the present invention, the heat input to the mixed powder etc. is much less 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 possible to form a metal composite layer with carbide-based ceramic particles dispersed only on any specific surface of the metal material, instead of dispersing the ceramic particles throughout the metal material as in the powder metallurgy method. A composite layer can be formed at low cost only on a desired surface of a metal material without substantially having an adverse thermal effect on the main part of the metal material. 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 (a combination of two or more metal powders) (including mixtures), it is possible to improve properties such as wear resistance by dispersing ceramic particles, and also 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 metal powder and carbon powder in the mixed powder disposed on the surface of the metal material in the thickness direction, for example, the portion of the composite layer closer to the metal material is 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 mixed powder melted by the high-density energy source is rapidly cooled primarily by heat absorption by the metallic material. According to this method, there is no need for a special cooling device for cooling the molten mixed powder, and since the surface of the molten mixed powder and the metal material heated to a high temperature is rapidly cooled, the matrix The metal crystals 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 mixed powder takes place in an inert atmosphere. According to this method, there are problems such as insufficient carbonization of the metal due to oxidation of the carbon powder, generation of pores in the composite layer, and problems such as oxidation of the metal powder and the formation of pores in the composite layer. It is possible to avoid problems such as oxidation of the matrix metal. 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 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 the metal powder or metal material is relatively high, and the 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 adjustment, and when mixed powder is melted, the molten metal It is superior to a laser in that the formed ceramic particles are stirred by electromagnetic stirring action. In addition, the atmosphere for electron beams generally must be a vacuum atmosphere, whereas the atmosphere for lasers and TIG arcs may be an inert gas atmosphere, so the equipment and work efficiency required to create and maintain the specified atmosphere are limited. Lasers and TIG arcs are preferred, and electron beams are superior to other high-density energy sources when such characteristics are required, since they have a very small heating area and can achieve large penetration depths. Therefore, according to yet another detailed feature of the method of the invention, depending on the type of metal powder, the shape, area, thickness, etc. of the composite layer to be formed, a laser, TIG, etc. can be used as the high-density energy source. Arc and electron beam can be used appropriately. The powder of the metal element highly reactive with carbon in the method of the present invention may be a single type of metal powder or a mixed powder of multiple types of metal powder, but a composite powder in which ceramic particles are uniformly dispersed may be used. Preferably, the metal powder and carbon powder are mixed substantially uniformly to form the layer. Metals that are highly reactive with carbon include Si, Cr, Ti, V, Zr, Al,
There are Mo, Mn, Ta, Nb, W, etc., and the reaction formula of these metal elements with carbon and the change in standard free energy ΔG゜ during carbide formation at 1500K are as shown in Table 1 below. be.

【table】

[Table] Also, according to the results of experimental research conducted by the inventors of the present invention, in order to easily melt the metal powder and to prevent the formation of pores in the composite layer, the average particle size of the metal powder must be The diameter is preferably 300μ or less, particularly 100μ or less, in order to form a uniform mixed powder of metal powder and carbon powder, thereby forming a composite layer in which ceramic particles are substantially uniformly dispersed. The average particle size of the carbon powder is preferably 0.1 to 200μ, particularly 0.1 to 100μ. Further, disposing the mixed powder of metal powder and carbon 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, and it is also possible to arrange the mixed powder on the surface of the metal material by simply disposing the mixed powder in a layered manner. 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 a powder compact of the mixed powder on a metal material, or to form grooves on the surface of the metal material and compact the mixed powder within the groove. , a paste is formed by adding a binder such as an aqueous solution of PVA (polyvinyl alcohol) or a mixture of cellulose and glycerin to the mixed powder, and the paste is attached to the surface of the metal material using the spatula coating method 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. It may be carried out by adhering to the surface of the metal material by coating, spraying, or dipping. 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 then 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 Chromium powder (purity 99.5%) with an average particle size of 50μ and graphite powder with an average particle size of 20μ are uniformly mixed, so that the atomic % ratio of these powders is 2:1.
A mixed powder having a weight ratio of 9:1 was formed. 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 Figure 1, 70 x 40 x 10
A specimen 1 made of tool steel (JIS standard SKD61) with dimensions of Arranged parallel to each other with a distance of 5 mm,
The paste 4 was filled between these guides by spatula application, so that the paste was arranged in a layer having a width of 5 mm and a thickness of 0.2 mm along the longitudinal direction at the center of the surface of the test piece. Next, although not shown in the figure, the test piece was kept at 100℃ for 0.5 hours in a drying oven to sufficiently dry the paste, which resulted in a porosity of about 40% as shown in Figure 2. A mixed powder layer 5 was formed on the test piece 1. Next, as shown in FIG. 3, argon as a shielding gas is emitted from the tip of the laser gun 6, thereby shielding the molten part on the test piece with argon and spreading the powder mixture from one end to the other end of the mixed powder layer 5. By scanning the laser gun 6 in one pass, the mixed powder layer is locally heated by the laser 7 under the conditions shown in Table 2 below, and the chromium powder is melted and chromium is carbonized. As shown in FIG. 1, a composite layer 8 made of a chromium alloy in which chromium carbide particles were dispersed was formed. In this case, the part of the test piece immediately below the mixed powder layer is also partially melted, and the resulting molten metal, the formed chromium carbide particles, and the surface of the test piece mainly absorb heat from the main part of the test piece. As a result, it was rapidly cooled. Table 2 Power density: 300 W/mm ² Energy density: 120 J/mm ² Scanning speed: 10 mm/sec Argon flow rate: 106/min The width of the composite layer formed as described above is 5.2 mm, and the maximum thickness is 0.4 It was warm in 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 10 between the composite layer 8 and the base metal 9 of the test piece, as schematically shown in FIG. Although it did exist, its width was approximately 0.5 to 0.7 mm. In addition, the volume fraction of chromium carbide particles 11 in the composite layer is approximately 15
% and was substantially uniform over the entire composite layer, and it was observed that the adhesion between the chromium particles and the chromium alloy 12 as the matrix metal and the integrity between the composite layer and the test piece were also good. Furthermore, the average particle size of the chromium carbide particles was about 2μ. FIG. 6 is an optical micrograph showing the metal structure at the center of the cross section of the longitudinal center of the composite layer 8 at 400 times magnification. In the figure, the white area is the chromium alloy as the matrix metal, and the black dotted areas are chromium carbide particles. From FIG. 6, it can be seen that fine chromium carbide particles of substantially uniform size are uniformly dispersed in the matrix metal, and defects such as pores are not generated at all. Example 2 Titanium powder with an average particle size of 44μ (purity 99.0%)
and graphite powder with an average particle size of 20 μ are uniformly mixed, so that the atomic % ratio of these powders is
A mixed powder of 1.5:1 (6:1 weight ratio) was formed. Then, by injecting a 5% aqueous solution of polyvinyl alcohol as a binder into the mixed powder,
A viscous paste similar to that of Example 1 was formed. Next, a test piece of the same size and 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 40 mm surfaces in the longitudinal direction. Width 5mm along, thickness 0.8
The paste was arranged in a layer of mm. Next, Example 1
By sufficiently drying the paste under the same conditions as in the case of Example 1, a mixed powder layer 13 having a porosity of 40% was formed on the test piece 14, as shown in FIG. Next, in the same manner as in Example 1, helium as a shielding gas is emitted from the tip of the laser gun, thereby shielding the molten part on the test piece with helium, and the laser gun is heated from one end of the mixed powder layer 13 to the other. By scanning in one pass, the mixed powder layer is locally heated with a laser under the conditions shown in Table 3 below, melting the titanium powder and carbonizing the titanium, as shown in Figure 8. Composite layer 1 made of a titanium alloy in which titanium carbide particles are dispersed as shown in FIG.
5 was formed. In this case, the part of the test piece immediately below the mixed powder layer is also partially melted, and the thus generated molten metal, the titanium carbide particles, and the surface of the test piece absorb heat mainly from the main part of the test piece. As a result, it was rapidly cooled. Table 3 Power density: 240W/mm ^2Energy density: 180J/mm ^2Scanning speed: 4mm/sec Helium flow rate: 100/min The width of the composite layer formed as described above is 5.4mm, and the maximum thickness is 1.6 It was warm in mm. In addition, when we observed the cross section of the central part of the test piece, we found that, as in Example 1, there was a heat-affected zone between the composite layer and the base metal of the test piece, but the width of the heat-affected zone was 0.8~ 1.0mm
It was moderately hot. In addition, the volume fraction of titanium carbide particles in the composite layer is approximately 25%, which is substantially uniform over the entire composite layer. It was also observed that the integrity was good. Furthermore, the average particle size of titanium carbide is approximately
It was 8μ. FIG. 9 is an optical micrograph showing the metal structure at the center of the longitudinal cross-section of the composite layer 15 at a magnification of 400 times. In the figure, the black to dark gray parts are titanium alloy parts as the matrix metal, and the white granular parts are titanium carbide particles. From FIG. 9, it can be seen that fine titanium carbide particles of relatively uniform size are uniformly dispersed in the matrix metal, and defects such as pores are not generated at all. 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 drawings]

Fig. 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; Fig. 2 is a perspective view showing the test piece with a mixed powder layer formed on the surface; Figure 3 is an illustration showing the process of melting the mixed powder layer on the test piece with a laser to form a composite layer, and Figure 4 is a perspective view showing the composite layer formed on the test piece by the process shown in Figure 3. figure,
Fig. 5 is an illustrative cross-sectional view showing a longitudinal cross-section of the central part of a test specimen on which a composite layer is formed, and Fig. 6 is a cross-sectional view of a composite layer made of a chromium alloy in which chromium carbide particles are dispersed. Optical micrograph showing the metal structure in the center at 400x magnification, Figure 7 is a perspective view of a test piece with a mixed powder layer formed on the surface, and Figure 8 shows the mixed powder layer in Figure 7 melted by a laser. Fig. 9 is an optical micrograph showing the metal structure at the center of the cross section of the composite layer made of a titanium alloy in which titanium carbide particles are dispersed, at a magnification of 400 times. . 1... Test piece, 2, 3... Guide, 4... Paste, 5... Mixed powder layer, 6... Laser gun, 7
... Laser, 8 ... Composite layer, 9 ... Base test piece, 10 ... Heat affected zone, 11 ... Chromium carbide particles, 12 ... Chromium alloy, 13 ... Mixed powder layer,
14...Test piece, 15...Composite layer.

Claims (1)

[Claims] 1. A powder of a metal element highly reactive with carbon and a carbon 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. A method for forming a metal composite layer in which carbide ceramic particles are dispersed by melting. 2. The method for forming a metal composite layer in which carbide ceramic particles are dispersed according to claim 1, wherein the molten mixed powder is rapidly cooled mainly by heat absorption by the metal material. Method for forming a dispersed metal composite layer. 3. In the method for forming a carbide-based ceramic particle-dispersed metal composite layer according to claim 1 or 2, the step of heating and melting the mixed powder with a high-density energy source is performed in an inert atmosphere. A method for forming a metal composite layer in which carbide-based ceramic particles are dispersed. 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. Formation method.