JPH0781161B2 - Method for producing metal-coated powder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a metal-coated powder having a metal layer on the surface of a core powder. More specifically, the present invention stably and reliably and economically obtains a metal-coated powder having excellent adhesion strength and uniform coating property that the core powder is not consumed even in a process such as sintering or thermal spraying. The present invention relates to a method for producing a metal-coated powder that can be used.

The metal-coated powder produced according to the present invention is an oil-impregnated bearing,
It can be applied to electrical contact materials, carbon brushes, sliding materials, friction materials, wear resistant materials, thermal spray materials, etc.

[Conventional technology and its problems]

Graphite powder, metal nitride powder, metal carbide powder,
The metal oxide powder or metal boride powder is mixed with the metal powder and then sintered to obtain oil-impregnated bearings, electrical contact materials, carbon brushes, sliding materials, friction materials, abrasion resistant materials, thermal spray materials, etc. It is formed and used in.

However, the graphite powder, the metal nitride powder, the metal carbide powder, the metal oxide powder, or the metal boride powder used here has a uniform mixed powder due to the difference in apparent density and surface state even when mixed with the metal powder. There is a drawback that you cannot get it. If the core powder is graphite powder, it has the disadvantage of being consumed during sintering or thermal spraying.If the core powder is a hard powder such as metal nitride powder, the life of the molding die will be reduced. There are drawbacks such as making it happen. Therefore, conventionally, a core powder whose surface is coated with a metal such as copper or nickel has been used. This metal coating is required to have uniform film-forming properties and adhesion that does not peel off when mixed or sprayed.

Conventionally, as a method of coating the core powder with copper, nickel, etc., a cementation method utilizing ion substitution, a method of depositing a metal with hydrogen etc. under high temperature and high pressure, or a platinum group-activated inorganic powder A method of performing electroless plating by cementation is known.

For example, as a method of coating the metal sulfide powder with copper,
A method utilizing a cementation reaction in which an acidic solution containing copper ions is added to a mixture of a metal less base than copper and a metal sulfide powder (Japanese Patent Publication No. 57-31532, 58-32201) is known. However, in the metal sulfide powder whose surface is hard to be activated, it is difficult to uniformly coat the copper layer and the adhesion strength is low.

As a method of pre-activating the metal sulfide powder to improve the above drawbacks, after coating the platinum group coating layer on the surface of the metal sulfide powder by thermal decomposition of the platinum group compound, the cementation reaction on the surface. A method of coating copper by utilizing it (Japanese Patent Publication No. 57-31533) has been proposed. However, this method is also essentially a substitution reaction between a base metal and copper, and there is a problem in uniform coating property and adhesion to coat the metal sulfide powder.

In addition, the core powder is dispersed in an ammoniacal solution containing soluble value nickel, treated in a reducing gas under high temperature and high pressure to obtain nickel-coated particles, which are then similarly treated using a solution containing soluble value cobalt. To coat nickel-coated particles with cobalt (Japanese Patent Application Laid-Open No. 55-132).
1) is proposed. However, this method increases the treatment cost and is not industrial because it is a hydrogen reduction reaction under high temperature and high pressure.

Furthermore, in order to solve these problems, core powder such as muscovite powder is immersed and activated in an aqueous solution of ferrous sulfate, stannous chloride, and silver nitrate, and hydrogen reduction is performed under high temperature and high pressure to obtain nickel, cobalt, copper, A method of coating with silver and palladium (JP-A-60-255902) has been proposed. However, this method has drawbacks in that the treatment is complicated, the control of the treatment liquid is difficult, and the hydrogen reduction reaction under high temperature and high pressure is similar to the method of Japanese Patent Publication No. 55-1321.

[Means for Solving the Problems]

As a result of various studies to solve the above-mentioned various problems of the prior art, the present inventor has finally completed the present invention capable of achieving the intended purpose.

The metal-coated powder produced according to the present invention has two types, one of which is the surface of any one kind of core powder selected from graphite powder, metal nitride powder, metal carbide powder, metal oxide powder or metal boride powder. The coating layer formed on the inner layer is one inner layer made of any one kind of low melting point metal selected from zinc, tin, lead or solder, and one outer layer made of any one kind metal selected from copper, nickel or cobalt. It is a type coated with and (hereinafter referred to as "double coating layer type"), and the other one is graphite powder, metal nitride powder, metal carbide powder,
A type in which the surface of any one kind of core powder selected from metal oxide powder or metal boride powder is covered with a layer in which the metal of the inner layer and the metal of the outer layer are mutually diffused or alloyed. (Hereinafter, referred to as "diffusion / alloy-reinforced type"). The latter is obtained by heat-treating the former, one that keeps the inner layer and the outer layer distinct from each other depending on the type of metal in the inner or outer layer and the heat treatment conditions (hereinafter referred to as "diffusion-type strengthening type"). The inner layer and the outer layer can be divided into those that do not maintain the distinction (hereinafter, referred to as “alloy type reinforced type”). In the diffusion-strengthened type, the metal of the inner layer and the metal of the outer layer which form the coating layer are mutually diffused at the interface between the inner layer and the outer layer, but the inner layer and the outer layer are still in a state of being classified. In addition, the alloy-type reinforced type is a further diffusion type of the diffusion-type reinforced type, in which the metal of the inner layer and the metal of the outer layer forming the coating layer are alloyed with each other, and the inner layer and the outer layer are no longer classified. Is not maintained. In addition, Example 12 described later
The metal-coated powder according to the present invention is also one in which the metal of the outer layer is softened in the state where the diffusion between the inner layer and the outer layer is maintained as shown in FIG.

Next, a method for producing the metal-coated powder according to the present invention will be described.

The method for producing a double-coated layer type metal-coated powder according to the present invention comprises a graphite powder, a metal nitride powder, a metal carbide powder, a metal oxide powder or a metal boride powder, and any one kind of core powder, Zinc powder, tin powder, lead powder, or any one kind of metal powder selected from solder powder is put into a container, and stirred while heating at a temperature above the liquid phase generation temperature of the metal powder to form a zinc layer on the surface of the core powder. , A tin layer, a lead layer, or a solder layer is coated with any one inner layer, and then the surface of the inner layer is coated with any one outer layer selected from a copper layer, a nickel layer, or a cobalt layer by chemical plating. Thus, a metal-coated powder in which the surface of the core powder is double-coated with an inner layer and an outer layer is obtained.

Further, the method for producing a diffusion-alloy-type reinforced metal-coated powder according to the present invention, by heating the metal-coated powder obtained by the method described above at 250 to 700 ° C. in a reducing atmosphere or an inert atmosphere. The present invention is characterized by obtaining a diffusion-type reinforced type or an alloy-type reinforced type.

Next, the configuration of the present invention will be described in detail.

Examples of the core powder in the present invention include graphite powder, metal nitride powder such as silicon nitride and boron nitride, metal carbide powder such as silicon carbide and titanium carbide, metal oxide powder such as aluminum oxide and tin oxide, and titanium boride. The metal borides may be mentioned.

The solder referred to in the present invention is a soft solder defined by ISO and is a tin-salt, tin-zinc, tin-silver, tin-copper, tin-antimony, lead-silver, zinc-silver alloy.

Zinc, tin, lead or solder is 1 to 50 with respect to the core powder.
wt% coverage is preferred. This is because if it is less than 1 wt%, uniform coating cannot be achieved, and if it exceeds 50 wt%, no improvement in properties is observed.

In the metal-coated powder according to the present invention, the core powder is zinc, tin,
Covered with lead or solder. Since these metals are cheaper than the platinum group metals used in one of the conventional methods, they can be coated in a large amount, and therefore the coating becomes uniform accordingly. Furthermore, zinc, tin, lead or solder is
It has good throwing power even with copper, nickel or cobalt, and has high adhesion strength.

Next, a method for producing a double coating layer type metal-coated powder according to the present invention will be described. In this production method, any one selected from a zinc layer, a tin layer, a lead layer or a solder layer on the surface of the core powder is used. It is roughly divided into a step of coating an inner layer of one layer and a step of coating an outer layer of any one layer selected from a copper layer, a nickel layer and a cobalt layer thereon.

To coat the inner layer on the surface of the core powder, vapor phase plating or hot dip coating can be applied. However, hot dipping is preferable in view of manufacturing cost, coating uniformity, and adhesion strength. By performing this hot dip plating, even if the core powder has a small particle diameter, the metal to be coated acts as a binder, so that the core powder is granulated or sized.

The core powder used in the present invention has almost no affinity with the metal of the inner layer as compared with the metal sulfide powder. Therefore, in the present invention, in order to increase the affinity between the core powder and the metal of the inner layer, an organic solvent is added when both are put into a container and stirred. By doing so, when the organic solvent is vaporized and decomposed, the pressure rises in an airtight container to create an inert reducing atmosphere, so that the adhesion strength between the core powder and the metal powder can be improved. it can. Further, since the metal of the inner layer can be prevented from being oxidized, the chemical plating in the next step can be easily progressed and the metal of the outer layer can be uniformly coated.

Examples of the organic solvent used include alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol or butyl alcohol, acetic acid esters such as methyl acetate, ethyl acetate, propyl acetate or butyl acetate, or methylene glycol, ethylene glycol, propylene glycol or It is a glycol such as butylene glycol or a polymer thereof. The amount of the organic solvent used is preferably 0.05 to 3% by weight with respect to the core powder and the metal powder. If the amount is less than 0.05% by weight, no effect is obtained, and if the amount is more than 3% by weight, the pressure increases, which may cause an explosion and is dangerous.

The specific method of hot dip plating is as follows. A core powder and any one kind of metal powder selected from zinc powder, tin powder, lead powder, and solder powder so as to have a predetermined coating amount are put into a closed rotary drum. At this time, if beads such as glass beads and stainless beads are added at the same time, the kneading property of the metal powder and the core powder is improved, and the beads serve as a heat medium, which facilitates plating. By rotating the rotating drum, the metal powder and the core powder are agitated and heated for 10 to 60 minutes at a temperature above the liquid phase generation temperature of the metal powder introduced by using a gas burner or the like. Since it is impossible to perform hot dipping at a temperature below the liquid phase generation temperature of the charged metal powder, it is necessary to heat above the temperature. If this heating is done in air, it must be treated below the decomposition temperature of the core powder. On the other hand, when heating in a reducing atmosphere or an inert atmosphere, higher temperature treatment is possible. After the heat treatment is finished, the mixture is cooled, and then the core powder coated with the inner layer is taken out separately from the beads.

By using the core powder coated with the inner layer obtained as described above, a uniform outer layer can be obtained with good plating efficiency.

Next, in order to coat the surface of the core powder coated with the inner layer with any one outer layer selected from a copper layer, a nickel layer or a cobalt layer, in addition to chemical plating, displacement plating, electroplating, vapor phase plating, etc. However, chemical plating is preferable in terms of ease of production and stability of quality. The processing conditions for chemical plating are different depending on the type of metal used, and will be described for each metal.

When copper is coated, the core powder coated with the inner layer is put into an alkaline solution of a complexing agent such as Rochelle salt, citric acid or ethylenediaminetetraacetic acid which causes a chelate bond with copper. Then, while stirring this, pH
Copper can be plated by gradually dropping a formalin solution and a copper compound aqueous solution while maintaining 10 to 13. The reaction temperature is 15 to 40 when using the Rossell salt bath.
C., 25 to 45.degree. C. in the citrate bath, and 25 to 60.degree. C. in the ethylenediaminetetraacetic acid bath. If the upper limit of the temperature is exceeded, the plating bath is easily decomposed and abnormally precipitated copper powder is present in the metal-coated powder, which may deteriorate the quality of the product. On the other hand, if the temperature does not reach the above lower limit, the plating reaction is difficult to proceed.

When nickel is coated, the core powder coated with the inner layer is put into an alkaline solution of a complexing agent such as a Rossell salt or a citrate as in the case of copper coating. Next, nickel is plated by gradually dropping a reducing agent selected from sodium hypophosphite, hydrazine, or hydrogen boride and an aqueous solution of a nickel compound while maintaining the pH at 8 to 13 with stirring. You can The reaction temperature is preferably 60 to 95 ° C. If it is lower than this temperature, the reaction is difficult to proceed, and if it is too high, the plating solution is easily decomposed.

When coating with cobalt, the same operation as nickel coating can be performed except that the pH is maintained at 11 to 13 and the aqueous cobalt compound solution is used as the metal source.

According to the above chemical plating method, substantially the entire amount of the injected metal is plated on the surface of the inner layer, and the desired outer layer can be easily formed with high precision, and the bath management is very easy. There is a feature called.

After the above-mentioned plating is completed, washing and drying are carried out to obtain the double coating layer type metal-coated powder produced by the present invention.

The double coating layer type metal-coated powder obtained by the above-mentioned method has good uniform coverage and adhesion. However, depending on the field of use, it may be desired to have stronger adhesion. For example, when used as a sintered metal or the like, it is necessary to prevent peeling of the coating layer when mixed with a different metal powder such as copper powder. The metal-coated powder which can satisfy such characteristics is the diffusion / alloy type reinforced type manufactured by the present invention. The manufacturing method will be described below. The double coating layer type metal-coated powder obtained by the above-mentioned method may be heated in a reducing atmosphere such as hydrogen or ammonia decomposition gas, or in an inert atmosphere such as nitrogen, nitrogen or helium. The heating conditions may be heat treatment at 250 to 700 ° C. for 10 minutes to several hours. If the heat treatment is performed at less than 250 ° C., diffusion or alloying or softening of the outer layer does not proceed sufficiently, so that it tends to be difficult to improve the adhesion. On the other hand, 700
When the temperature is higher than 0 ° C., the metal-coated powder itself tends to sinter, and when the thus-sintered powder is treated with a pulverizer, the coating layer is crushed and the core powder is exposed.

When the double-coated layer type metal-coated powder is heat-treated at a predetermined temperature in this manner, the inner layer metal and the outer layer metal shrink due to sintering. During this sintering, mutual diffusion or alloying of the inner layer metal and the outer layer metal proceeds. this is,
It is presumed that this is caused by the fact that the metal deposition particles by hot dipping and the coated metal deposition particles by chemical plating are extremely fine, dense and highly active. Whether diffusion or alloying occurs is determined by the heat treatment conditions of the double coating layer type metal-coated powder. In the case of a specific combination of the metal of the inner layer and the metal of the outer layer (for example, the inner layer is lead and the outer layer is copper), mutual diffusion or alloying hardly occurs. However, also in this case, the heat treatment described above removes the strain in the outer layer caused by the chemical plating to soften the outer layer, and as a result, the outer layer can be stabilized. However, the mutual diffusion or alloying of the metal of the inner layer and the metal of the outer layer, depending on the kind of the metal of the inner layer or the outer layer and the heat treatment conditions, becomes a diffusion-type strengthening type that maintains the division between the inner layer and the outer layer, It may be an alloy type reinforced type that does not keep the division between the inner layer and the outer layer.

The diffusion-alloy-reinforced metal-coated powder thus obtained has almost no peeling of the copper, nickel or cobalt layer even when mixed with a different metal powder.

〔Example〕

 Next, the configuration of the present invention will be described based on examples.

Example 1 20 g of commercially available graphite powder (PAG-120 manufactured by Nippon Graphite Co., Ltd.) and solder (tin 92) were placed in a closed rotary drum (500 ml capacity).
% -Zinc) powder 5 g, butyl alcohol 0.3 ml, and alumina beads (diameter 2 mm) 8 g are charged, and heat treatment is performed at 210 ° C for 30 minutes with a gas burner while rotating the drum, and the surface of the graphite powder is solder (tin). A powder coated with a (zinc) layer was obtained.

Next, after sifting this powder, Roussel salt (150 g
/) Add to 200 ml of solution, cupric chloride solution (as copper 25
g, 10% solution) and formalin 35% solution
The pH was adjusted to 12.0 to 12.5 and the temperature was adjusted to 20 to 25 ° C, and plating was performed by dropping. Then, after filtering and drying, 50 g of copper-solder (tin-zinc) -coated graphite powder in which the surface of the solder (tin-zinc) layer was coated with a copper layer was obtained.

The copper ion concentration in the liquid after the reaction was 0.02 ppm, about 100% of the injected copper ions were plated, and the color tone and throwing power were also satisfactory.

Example 2 20 g of the copper-solder (tin-zinc) coated graphite powder obtained in Example 1 was mixed with 70 vol% hydrogen gas and 30 vol% nitrogen gas.
After heat treatment at 250 ℃ for 30 minutes in the atmosphere, copper and solder (tin-zinc) were alloyed at the interface between the copper forming the outer layer and the solder forming the inner layer (tin-zinc) A reinforced copper-tin-zinc coated graphite powder was obtained.

Example 3 A commercially available α-silicon nitride powder (manufactured by Toshiba Ceramic: A-100 average particle size 1 μ) was added to the closed rotary drum used in Example 1.
g, solder (tin 63% -lead) powder 2 g, ethyl alcohol 0.5 ml, glass beads (diameter 2 mm) 5 g, and 1 with a gas burner
The powder was heated at 90 ° C. for 60 minutes to obtain a powder in which the surface of the silicon nitride powder was covered with a solder (tin-lead) layer.

Next, copper sulphate (as copper
51 g, 10% solution) and a formalin plating solution,
Also, as a complexing agent, 2Na-ethylenediaminetetraacetic acid (150 g /
) Using 250 ml, chemical plating was performed in the same manner as in Example 1. As a result, 73 g of copper-solder (tin-lead) coated silicon nitride powder in which the surface of the solder (tin-lead) layer described above is coated with a copper layer
Got

Example 4 20 g of copper-solder (tin-lead) coated silicon nitride powder obtained in Example 3 was heat-treated at 400 ° C. for 60 minutes in a hydrogen gas atmosphere,
The outer layer of copper and the inner layer of solder (tin-
A reinforced copper-tin-lead alloy-coated silicon nitride powder alloyed with lead was obtained.

Example 5 20 g of aluminum oxide powder (manufactured by Merck & Co., Inc .: aluminum oxide-90), 10 g of tin powder, 0.7 ml of isopropyl alcohol, and 5 g of glass beads were placed in the closed rotary drum used in Example 1 and placed in a gas burner. Then, heat treatment was performed at 230 ° C. for 45 minutes to obtain a powder in which the surface of the aluminum oxide powder was covered with a tin layer.

Next, the surface of this powder was subjected to chemical plating in the same manner as in Example 1 so that the copper coverage was 60%, and the copper-tin-coated aluminum powder in which the copper layer was coated on the surface of the tin layer described above.
Obtained 75 g.

Example 6 20 g of copper-tin coated aluminum powder obtained according to Example 5
Was heat-treated in argon gas at 600 ° C. for 45 minutes to obtain a reinforced copper-tin alloy-coated aluminum powder in which copper forming the outer layer and tin forming the inner layer were alloyed.

Example 7 In the sealed rotary drum (500 ml capacity) used in Example 1,
Commercially available graphite powder (Nippon Graphite Co., Ltd .: CB-100)
20 g, solder (tin 63% -lead) powder 2 g, butyl acetate 0.3 ml, and alumina beads (diameter 2 mm) 5 g were charged, and heat treatment was performed with a gas burner at 360 ° C for 60 minutes while rotating the drum, and graphite powder A powder whose surface was coated with a solder (tin-lead) layer was obtained.

Next, a plating solution containing cupric chloride solution (22 g of copper, 10% solution) and formalin 35% solution was used so that the copper coating amount was 50%, and a Rossell salt (150 g) was used as a complexing agent. /
) 200 ml was used for chemical plating in the same manner as in Example 1. As a result, a copper-solder (tin-lead) -coated graphite powder in which the surface of the solder (tin-lead) layer described above is coated with a copper layer
I got 44g.

Example 8 20 g of the copper-solder (tin-lead) -coated graphite powder obtained in Example 7 was heat-treated at 400 ° C. for 20 minutes in a hydrogen gas atmosphere to form the inner layer of copper and the outer layer of copper. A reinforced copper-tin-lead alloy-coated graphite powder alloyed with solder (tin-lead) was obtained.

Example 9 A commercially available muscovite powder (muscovite powder, average particle size 170 μ, average thickness 8) was placed in the closed rotary drum used in Example 1.
μ) 20g, zinc powder 7g, methyl alcohol 0.20ml, glass beads 20g, and heat-treated at 430 ° C for 30 minutes with a gas burner to obtain a powder in which the surface of the muscovite powder was coated with a zinc layer. .

Next, after sifting this powder, Roussel salt (150 g
/) Add to 250ml solution, nickel chloride (27g as nickel, 10% solution) and sodium hypophosphite solution (10%
Solution) containing a plating solution of pH 11.0 to 11.5, temperature 80 to 85 ° C
The plating was carried out by dripping while adjusting to. Then, after filtration and drying, 54 g of nickel-zinc coated muscovite powder in which the surface of the zinc layer was coated with a nickel layer was obtained.

The nickel ion concentration in the liquid after the reaction was 0.03 ppm, and almost all the injected nickel ions were plated, and the color tone and throwing power were also satisfactory.

Example 10 20 g of the nickel-zinc coated muscovite powder obtained in Example 9 was heat-treated in hydrogen gas at 550 ° C. for 60 minutes at the interface between nickel forming the outer layer and zinc forming the inner layer. A reinforced nickel-zinc coated muscovite powder obtained by alloying nickel and zinc was obtained.

Example 11 To the closed rotary drum used in Example 1, 20 g of commercially available zirconium oxide ore powder (battery stone powder), 0.5 g of lead powder, 0.1 ml of propyl alcohol, and 10 g of alumina beads (diameter 2 mm) were charged, and a gas burner was added. Was heated at 320 ° C. for 1 hour to obtain a powder in which the surface of the battery stone powder was covered with a lead layer.

Next, to this powder, nickel sulfate (20.5 g of nickel, 10% solution) and sodium borohydride solution (10% solution) were individually added dropwise so that the coating amount of nickel would be 50%.
The plating was performed while adjusting the pH to 10.5 to 11.0 and the reaction temperature to 80 to 85 ° C. A sodium citrate solution was used as the alkali complexing agent.

As a result, 40 g of nickel-lead-coated zirconium oxide ore powder in which the surface of the nickel layer was coated with the lead layer was obtained.

Example 12 20 g of nickel-lead-coated zirconium oxide ore powder obtained according to Example 11 was heat-treated at 450 ° C. for 30 minutes in an argon gas atmosphere, and the nickel forming the outer layer was softened to form a reinforced nickel-lead coating. Zirconium oxide ore powder was obtained.

Example 13 In the sealed rotary drum used in Example 1, 20 g of commercially available titanium nitride powder (NiN-02: TiN-02), solder (tin)
96.5 g-Silver) powder 1 g, butyl alcohol 0.5 ml, alumina beads 15 g (diameter 2 mm) were charged, and the gas burner was operated at 225 ° C, 60
Heat treatment was performed for a minute to obtain a powder in which the surface of the titanium nitride powder was covered with solder (tin-silver).

Next, nickel chloride (21 g of nickel, 10% solution) and hydrazine hydrochloride solution (10% solution) were used as plating solutions so that the nickel coating amount was 60%, and Rochelle salt (150 g
/) 300 ml as complexing agent pH 11.5 ~ 12.0, reaction temperature 80 ~ 8
Chemical plating was performed while adjusting to 5 ° C.

As a result, 41 g of nickel solder (tin-silver) -coated titanium nitride powder in which the surface of the solder (tin-silver) layer was coated with a nickel layer was obtained.

Example 14 20 g of the nickel-solder (tin-silver) -coated titanium nitride powder obtained in Example 13 was heat-treated at 400 ° C. for 60 minutes in a nitrogen gas atmosphere to obtain an inner solder layer (tin-silver) and an outer nickel layer. A reinforced nickel-solder (tin-silver) alloy-coated titanium nitride powder was obtained which was alloyed with the layers.

Example 15 In the closed rotary drum used in Example 1, 20 g of commercially available titanium boride powder (manufactured by Nippon Shinkin Co., Ltd.) and solder (tin 99.2%-) were used.
Copper powder 2.0g, polyethylene glycol 1ml, glass beads 5
Then, g was added and heat treatment was performed at 390 ° C. for 60 minutes with a gas burner to obtain a powder in which the surface of the titanium boride powder was covered with a solder (tin-copper) layer.

Next, cobalt chloride (33 g as cobalt, 10% solution) and sodium hypophosphite solution (10% solution) were used as plating solutions so that the coating amount of cobalt was 60%, and sodium citrate solution (150 g /) 250 ml as complexing agent pH12.0〜
Chemical plating was performed while adjusting the reaction temperature to 12.5 and the reaction temperature to 85-90 ℃.

As a result, 64.5 g of cobalt-solder (tin-copper) -coated titanium boride powder in which the cobalt layer was coated on the surface of the solder (tin-copper) layer was obtained.

Example 16 20 g of cobalt-solder (tin-copper) -coated titanium boride powder obtained in Example 15 was mixed with 70 vol% hydrogen gas and 30 vol% nitrogen gas.
Heat treatment at 500 ° C for 60 minutes in a mixed atmosphere, and then solder (tin-
A strengthened cobalt-solder (tin-copper) alloy titanium boride powder in which copper) and a cobalt layer were alloyed was obtained.

Example 17 20 g of a commercially available tungsten carbide powder (manufactured by Nippon Shinkin Co., Ltd.) and tin powder were placed in the closed rotary drum used in Example 1.
1 g, 0.5 ml of propyl alcohol, and 10 g of glass beads were added, and heat treatment was performed with a gas burner at 250 ° C. for 30 minutes to obtain a powder in which the surface of the tungsten carbide powder was covered with a tin layer.

Next, cobalt sulfate (21 g as cobalt, 10% solution) and hydrazine sulfate solution (10% solution) were used as plating solutions so that the coating amount of cobalt was 50%, and 250 ml of Rossell salt solution (150 g /) was used. Chemical plating was performed while adjusting the pH as a complexing agent to 11.5-12.0 and the reaction temperature as 85-90 ℃.

As a result, 40.6 g of cobalt-tin-coated tungsten carbide powder in which the cobalt layer was uniformly coated on the surface of the tin layer was obtained.

Example 18 20 g of the cobalt-tin-coated tungsten carbide powder obtained in Example 17 was heat-treated in hydrogen gas at 550 ° C. for 60 minutes to form an alloy of cobalt forming the outer layer and tin forming the inner layer. A strengthened cobalt-tin alloy coated tungsten carbide powder was obtained.

Example 19 In a closed rotary drum (500 ml capacity), 20 g of commercially available graphite powder (PAG-120 manufactured by Nippon Graphite Co., Ltd.) and solder (tin 92)
% -Zinc) powder 5g and alumina beads (diameter 2mm) 8g are put in, 210 ° C, 30 with a gas burner while rotating the drum.
Heat treatment was performed for a minute to obtain a powder in which the surface of the graphite powder was covered with a solder (tin-zinc) layer.

Then, the same treatment as in Example 1 was carried out to obtain 50 g of copper-solder (tin-zinc) -coated graphite powder in which the surface of the solder (tin-zinc) layer was coated with a copper layer.

The copper ion concentration in the liquid after the reaction was 0.02 ppm, about 100% of the injected copper ions were plated, and the color tone and throwing power were good.

Example 20 20 g of the copper-solder (tin-zinc) -coated graphite powder obtained in Example 1 was mixed with 70 vol% hydrogen gas and 30 vol% nitrogen gas.
After heat treatment at 250 ℃ for 30 minutes in the atmosphere, copper and solder (tin-zinc) were alloyed at the interface between the copper forming the outer layer and the solder forming the inner layer (tin-zinc) A copper-tin-zinc coated graphite powder was obtained.

Example 21 In the closed rotary drum used in Example 1, commercially available muscovite powder (muscovite powder, average particle size 170μ, average thickness 8) was used.
μ) 20 g, zinc powder 7 g, and glass beads 20 g were charged, and heat treatment was performed at 430 ° C. for 30 minutes with a gas burner to obtain a powder in which the surface of the muscovite powder was coated with a zinc layer.

Then, the same treatment as in Example 9 was carried out to obtain 54 g of nickel-zinc coated muscovite powder in which the surface of the zinc layer was coated with a nickel layer.

The nickel ion concentration in the liquid after the reaction was 0.03 ppm, and almost all the injected nickel ions were plated, and the color tone and throwing power were good.

Example 22 20 g of nickel-zinc coated muscovite powder obtained according to Example 21 was heat-treated in hydrogen gas at 550 ° C. for 60 minutes at the interface between nickel forming the outer layer and zinc forming the inner layer. A reinforced nickel-zinc coated muscovite powder obtained by alloying nickel and zinc was obtained.

Example 23 Commercially available tungsten carbide powder (manufactured by Nippon Shinkin Co., Ltd.) 20 g and tin powder were placed in the closed rotary drum used in Example 1.
Add 1g and 10g of glass beads, and 250 ℃ with a gas burner.
Heat treatment was performed for 30 minutes to obtain a powder in which the surface of the tungsten carbide powder was covered with a tin layer.

Next, the same chemical plating as in Example 15 was performed.

As a result, 40.6 g of cobalt-tin-coated tungsten carbide powder in which the cobalt layer was uniformly coated on the surface of the tin layer was obtained.

Example 24 20 g of the cobalt-tin-coated tungsten carbide powder obtained in Example 23 was heat-treated in hydrogen gas at 550 ° C. for 60 minutes to form an alloy of cobalt forming the outer layer and tin forming the inner layer. A strengthened cobalt-tin alloy coated tungsten carbide powder was obtained.

Table 1 shows the peeling test results of the coating layer and the peeling layer of the metal-coated powder obtained in Examples 1 to 24 and the constitution XMA of the coating layer.

* 1: By observation with a stereomicroscope (250 magnification), the proportion of the completely covered powder in the whole was randomly sampled from 5 fields of view and determined by the average value.

* 2: The metal-coated powder obtained in Examples 1 to 24 was targeted.

* 3: The object was 70 VOL% of the metal-coated powder obtained in Examples 1 to 24, which was mixed with 30 VOL% of glass beads (diameter 2 mm) by rotation for 1 hour and then sifted.

〔The invention's effect〕

Since the present invention is configured as described above, the following effects are exhibited. That is, the double coating layer type metal-coated powder produced according to the present invention has zinc, tin, lead or solder present on the surface of the core powder. Very little exposure of the surface of the core powder. Therefore, the throwing power of copper, nickel, or cobalt of the outer layer is improved, so that the uniformity is good and the adhesion strength is high. Further, the diffusion-alloy-type reinforced metal-coated powder produced according to the present invention is made of zinc, tin, lead or solder, which forms one inner layer, and one copper layer, which forms an outer layer. , Nickel or cobalt is diffused or alloyed, so that stronger adhesion can be provided.

A method for producing a double-coated layer type metal-coated powder according to the present invention comprises forming an inner layer of any one layer selected from a zinc layer, a tin layer, a lead layer and a solder layer on a surface of a core powder by a hot dip plating method. Since an outer layer of any one layer selected from a copper layer, a nickel layer or a cobalt layer is formed on the surface of these metal layers by the chemical plating method, the treatment can be performed easily and inexpensively, and the bath management is also easy. Is. Also. Since the method for producing the diffusion-alloy-type reinforced metal-coated powder according to the present invention only heat-treats the double-coated layer-type metal-coated powder at a relatively low temperature, a metal-coated powder having high adhesion strength can be easily prepared. Obtainable.

Therefore, the present invention makes a great contribution to the industrial production for metallization of ceramic powder such as graphite powder, metal nitride powder, metal carbide powder, metal oxide powder or metal boride powder.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location C01B 35/04 Z C23C 18/31 A (72) Inventor Osamu Iwazu Mikage Yamate, Higashinada-ku, Kobe city, Hyogo prefecture 1-3-2 (56) Reference JP-A-55-53017 (JP, A) JP-A-63-18096 (JP, A)

Claims (7)

[Claims] 1. A core powder selected from graphite powder, metal nitride powder, metal carbide powder, metal oxide powder or metal boride powder, and zinc powder, tin powder, lead powder or solder powder. One kind of metal powder is placed in a container and stirred while being heated to a liquidus generation temperature of the metal powder or higher, and the surface of the core powder is selected from a zinc layer, a tin layer, a lead layer or a solder layer. It is coated with any one inner layer, and then the surface of the inner layer is coated with any one outer layer selected from a copper layer, a nickel layer or a cobalt layer by chemical plating, and the surface of the core powder is covered with the inner layer and the outer layer. A method for producing a metal-coated powder, which comprises obtaining a metal-coated powder that is double-coated. 2. Alcohols such as methyl alcohol, ethyl alcohol, propyl alcohol or butyl alcohol, acetic acid esters such as methyl acetate, ethyl acetate, propyl acetate or butyl acetate, or methylene glycol, ethylene glycol, propylene glycol or butylene glycol. The method for producing a metal-coated powder according to claim 1, wherein an organic solvent selected from glycols such as the above or a polymer thereof is charged into a container together with the core powder and the metal powder. 3. A core powder coated with an inner layer is added to a solution of a complexing agent selected from Rossel's salt, citrate or ethylenediaminetetraacetic acid adjusted to pH 10 to 13, and then stirred while stirring. 3. The metal-coated powder according to claim 1, wherein the formalin and the copper compound aqueous solution are added while maintaining the pH to obtain a metal-coated powder in which the surface of the core powder is double-coated with an inner layer and an outer layer. Method for producing coated powder. 4. A core powder coated with an inner layer is added to a solution of a complexing agent selected from a Rochelle salt or a citrate adjusted to pH 8 to 13, and then the above mixture is stirred and maintained at the above pH. A reducing agent selected from sodium hypophosphite, hydrazine, or borohydride and an aqueous nickel compound solution are added to obtain a metal-coated powder in which the surface of the core powder is double-coated with an inner layer and an outer layer. The method for producing a metal-coated powder according to claim 1 or 2, which is characterized in that. 5. A core powder coated with an inner layer is added to a solution of a complexing agent selected from a Rochelle salt or a citrate adjusted to pH 11 to 13, and then stirred while maintaining the above pH. A reducing agent selected from sodium hypophosphite, hydrazine, or borohydride and an aqueous cobalt compound solution are added to obtain a metal-coated powder in which the surface of the core powder is double-coated with an inner layer and an outer layer. The method for producing a metal-coated powder according to claim 1 or 2, which is characterized in that. 6. A metal in which the surface of a core powder is double-coated with one inner layer and one outer layer by the method for producing a metal-coated powder according to any one of claims 1, 2, 3, 4, and 5. Coated powder is obtained and the powder is placed in a reducing or inert atmosphere.
By heating at 250-700 ° C, the metal of the inner layer and the metal of the outer layer are mutually diffused or alloyed in the state that the inner layer and the outer layer are not maintained. A method for producing a metal-coated powder, characterized in that the metal-coated powder is made into a metal. 7. A metal in which the surface of a core powder is double-coated with one inner layer and one outer layer by the method for producing a metal-coated powder according to any one of claims 1, 2, 3, 4, and 5. A coating powder is obtained, which powder is used in a reducing or inert atmosphere for 25
A method for producing a metal-coated powder, comprising heating at 0 to 700 ° C. to obtain a metal-coated powder in which the metal of the outer layer is softened while maintaining the division between the inner layer and the outer layer.