JPH04128301A - Co-base alloy powder and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture Co-base alloy powder capable of manufacturing a high strength sintered body and having excellent wear resistance by interposing an annular layer constituted of the aggregate of fine oxide hard particles between a center part and a peripheral part in a Co-base alloy powder base material. CONSTITUTION:After executing an oxidizing treatment to the Co-base alloy powder raw material incorporating 1-30wt.% oxidizing element by holding at 1050-1350 deg.C for the prescribed time in an oxidizing atmosphere, reducing treatment is executed by holding at 200-500 deg.C for the prescribed time in a reducing atmosphere. By this method, in all cross sections passing through the powder center part, the Co-base alloy powder having the annular layer constituted of the aggregate of fine oxide hard particles between the powder center part and the powder peripheral part, is obtd. Then, the oxidizing element uses one or two more kinds of Al, Si, Ti, V, Cr, W, Hf, Be, Nb, Zr. By this method, the Co-base alloy powder for which the high strength sintered body is manufactured by sintering, is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a Co-based alloy suitable for use as a raw material powder when producing a sintered body that requires wear resistance, particularly by powder metallurgy. This invention relates to powders and their manufacturing methods.

[Conventional technology]

Conventionally, as a method for manufacturing a sintered body that requires wear resistance using a powder metallurgy method, for example, Co is used as a raw material powder.
powder or Co-based alloy powder, and Y.

Al1, Zr. Using one or more oxide hard powders of oxides such as
A method for producing a Co-based alloy sintered body in which fine oxide hard particles are uniformly distributed on a base of Co or Co-based alloy by mixing, press-forming into a green compact, and sintering the green compact. It has been known.

[Problem to be solved by the invention]

However, in the above-mentioned conventional wear-resistant Co-based alloy sintered bodies, the hard oxide particles tend to fall off during practical use because the adhesion of the hard oxide particles to the base of Co or Co-based alloy is insufficient. As a result, the wear progresses quickly, and the hard oxide particles that fall off can damage the mating material.

[Means to solve the problem]

Therefore, from the above-mentioned viewpoint, the present inventors focused on the raw material powder used for manufacturing the sintered body in order to develop a sintered body with excellent wear resistance, and as a result of their research, they found that oxidizing elements , that is, an element that forms a solid solution with Co and has a greater affinity for oxygen than Co, preferably A, l? ,S
i, Ti, V, Cr, W, Hf, Be.

One or more of Nb and Zr
Co-based alloy powder material containing ~30% by weight and further containing Fe and/or N1 as an alloying component as necessary, is maintained at a temperature of 1050 to 1350°C for a predetermined time in an oxidizing atmosphere under the following conditions. When oxidation treatment is performed, preferably in a powder fluidized state, fine Co and the above particles are formed between the powder center and the powder periphery in every cross section passing through the powder center on the base material mainly consisting of cobalt oxide. An oxide powder having an annular layer composed of aggregates mainly composed of composite oxides of oxidizing elements is formed, and this oxide powder is then heated to 200 to 500 ml in a reducing atmosphere. When the reduction treatment is carried out under the conditions of holding at a temperature of The composite oxide of the oxidizing element also changes into hard oxide particles mainly composed of the oxide of the oxidizing element, and as a result, any cross section passing through the center of the powder is formed on the base made of Co or Co-based alloy. In this process, a Co-based alloy powder is formed in which an annular layer composed of aggregates of fine oxide hard particles exists between the powder center and the powder periphery. When a sintered body is manufactured using this as a raw material powder, the oxide hard particles in the sintered body are formed by the oxidation-reduction reaction of the oxidizing element contained as an alloy component as described above. Therefore, the adhesion to the substrate is extremely high, and falling off is significantly suppressed during practical use, resulting in excellent abrasion resistance.Furthermore, there are virtually no hard oxide particles on the powder surface, and there are no layers inside. Since it has a shell-like distributed structure, the sintered body is not damaged, and the research results show that it is possible to manufacture a sintered body with high strength.

This invention was made based on the above research results. In addition, fine oxide hard particles, namely C
Fine oxide hard particles formed of an oxide of an oxidizing element that forms a solid solution with Co and has a greater affinity for oxygen than Co, preferably Al.

Si, Ti, V, Cr, W, Hf, Be, Nb.

Co-based alloy powder in which an annular layer consisting of an aggregate of fine oxide hard particles composed of one or more of the oxides of Z and Z is present.

(2) An oxidizing element, that is, an element that forms a solid solution with Co and has a greater affinity for oxygen than Co, preferably AN,
Si, Ti, V, Cr, W, Hf.

A Co-based alloy powder material containing 1 to 30% by weight of an oxidizing element consisting of one or more of Be, Nb, and Zr is maintained at a temperature of 1050 to 1350°C for a predetermined time in an oxidizing atmosphere. Under the following conditions, preferably in a powder fluidized state, oxidation treatment is applied to the base material mainly consisting of nickel oxide, so that fine particles are formed between the powder center and the powder periphery in every cross section passing through the powder center. An oxide powder is formed in which an annular layer mainly composed of a composite oxide of Co and the above oxidizing element exists, and then the oxide powder is heated at 200 to 500 °C in a reducing atmosphere. The temperature is maintained for a predetermined period of time, and a reduction treatment is performed under the following conditions to reduce the base material mainly composed of nickel oxide to Co or a Co-based alloy, and at the same time, the annular layer composed of the aggregates of the above composite oxide is removed from the main body. A method for producing a Co-based alloy powder, which is transformed into an annular layer composed of fine oxide hard particles made of an oxide of the above-mentioned oxidizing element.

It has the following characteristics.

Next, the reason why the manufacturing conditions are limited as described above in the method for manufacturing Co-based alloy powder of the present invention will be explained.

(a) Content of oxidizing elements Oxidizing elements combine with oxygen to form hard oxide particles that form a layer inside the powder and are aggregated and distributed in a shell shape, without impairing the sinterability of the powder. , and has the effect of significantly improving the wear resistance of a sintered body manufactured using this as a raw material powder, but if its content is less than 1% by weight, the formation rate of oxide hard particles is insufficient and the desired level cannot be achieved. On the other hand, if the content exceeds 30% by weight, the proportion of hard oxide particles formed becomes too large, and their coarsening is unavoidable. Since the sintered body produced using the sintered body becomes aggressive towards the other party, its content was determined to be 1 to 30% by weight.

(b) Oxidation treatment temperature If the temperature is lower than 1050°C, the complex oxide of Co and oxidizing elements will not form a ring-shaped agglomeration sufficiently, while if the temperature exceeds 1350°C, the powders will not commotion even if they are fluidized. The temperature is set at 1050 to 1
The temperature was set at 350°C.

(c) Reduction treatment temperature If the temperature is less than 200°C, it will take a long time to reduce the oxide powder, which is undesirable in actual operation;
If the temperature exceeds 0°C, a reduction reaction is likely to occur even in the hard oxide particles, so the temperature was set at 200 to 500°C.

〔Example〕

Next, the Co-based alloy powder of the present invention and the method for producing the same will be specifically explained with reference to Examples.

Using atomized Co-based alloy powder materials having the average particle size and composition shown in Table 1, these C
Methods 1 to 10 of the present invention were carried out by subjecting the O-based alloy powder material to oxidation treatment and reduction treatment under the conditions shown in Table 1 to produce Co-based alloy powders 1 to 10 of the present invention, respectively.

Accordingly, the resulting Co-based alloy powders 1 to I of the present invention
Regarding O, its cross-sectional structure was examined using a metallurgical microscope (magnification: 10
00 times), and measured the particle size on an arbitrary straight line passing through the center of the cross section of each of the 30 powders, as well as the outer diameter and inner diameter of the annular layer, calculated the average value of these, and It is shown in Table 2.

Furthermore, the resulting Co-based alloy powder of the present invention 1 to 5 nm in average particle size Al2O3 powder, 5 mm MgO powder, and 3Hn Y2O3 powder were used as raw material powders for forming the hard phase of the sintered body. Furthermore, the same 50un of Co powder was also used as the raw material powder, and these raw material powders were blended into the composition shown in Table 3, mixed 24 hours a day in a ball mill, dried, and then compressed at a pressure of 5 ton/c-. Co-based alloy sintered bodies using each of the Co-based alloy powders 1 to 10 of the present invention are obtained by molding into a powder and sintering this compact in a hydrogen atmosphere at a temperature of 1300°C for 30 minutes. Examples 1 to IO (hereinafter referred to as sintered bodies of the present invention) and conventional sintered bodies 1 to 3 were manufactured, respectively.

Table 1: For the purpose of evaluating the strength of these various sintered bodies, tensile strength was measured and an abrasion test was conducted.

The wear test was carried out on a cast iron (F
8m from the above sintered body from above the heat treated ring made of Cl2> (hardness: HRC50)! A test piece cut out to a size of 8 mm x 35 mm was brought into contact with the test piece horizontally, and in this state, a load of 5 kg was applied vertically to the test piece, and the ring was moved 1.
The test piece was rotated at a circumferential speed of 2 m/sec, and the maximum wear depth of the test piece was measured after 10 minutes.

These results are shown in Table 3.

〔Effect of the invention〕

From the results shown in Tables 1 to 3, according to methods 1 to 10 of the present invention, an annular layer composed of aggregates of fine oxide hard particles formed by an oxidation-reduction reaction was formed inside the powder. It is possible to produce existing Co-based alloy powders, and the resulting Co-based alloy powders 1 to IO inhibit sinterability when a sintered body is produced using them as raw material powders. Since the hard oxide particles are sealed inside the powder, good sinterability can be ensured, making it possible to produce a high-strength sintered body. When a sintered body manufactured using powders 1 to 10 is placed in an abrasion environment, the annular layer of oxide hard particles appearing on the worn surface acts as a single hard particle, that is, the annular layer Because it acts as a hard particle with a size equivalent to the outer diameter of In all of the sintered bodies 1 to 3, the adhesion of the hard oxide particles to the base material is poor, so it is easy to fall off and it is clear that wear progresses quickly.

As described above, according to the method of the present invention, it is possible to produce a Co-based alloy powder in which fine oxide hard particles form a layer inside the powder and are sealed in a shell shape, and therefore, the produced Co-based alloy powder has extremely good sinterability, and sintered bodies manufactured using it have high strength. Because it is formed by a reaction, it has high adhesion to the base of Co or Co-based alloy, and in addition, in the sintered body, it acts as hard particles with dimensions equal to the outer diameter of the annular layer, making it an excellent material. In addition to exhibiting wear resistance, the central part of the annular layer suppresses the aggressiveness of opponents, and is used in various drives such as sintered bearings, block rings, rocker arm tips, brake butts, and clutch plates that require these characteristics. It brings about industrially useful effects, such as exhibiting excellent performance when used as a raw material powder for manufacturing structural members of devices.

Claims (7)

[Claims] (1) On a base made of Co or Co-based alloy, in every cross section passing through the powder center, there is an annular layer composed of aggregates of fine oxide hard particles between the powder center and the powder periphery. A Co-based alloy powder characterized in that it exists. (2) the oxide hard particles form a solid solution with Co;
The Co-based alloy powder according to claim (1), characterized in that it is made of an oxide of an oxidizing element that has a greater affinity with oxygen than Co. (3) The oxide hard particles include Al, Si, Ti, V,
The Co-based alloy powder according to claim (1), characterized in that it comprises one or more of oxides of Cr, W, Hr, Be, Nb, and Zr. (4) A Co-based alloy powder material containing 1 to 30% by weight of oxidizing elements is subjected to oxidation treatment under the conditions of holding at a temperature of 1050 to 1350°C for a predetermined period of time in an oxidizing atmosphere, so that the main component is cobalt oxide. In every cross section passing through the powder center, between the powder center and the powder periphery, there is an annular layer composed of aggregates mainly composed of fine Co and composite oxides of the above-mentioned oxidizing elements. The existing oxide powder is formed, and then the oxide powder is subjected to a reduction treatment under the following conditions: held at a temperature of 200 to 500°C for a predetermined period of time in a reducing atmosphere to form a matrix mainly composed of cobalt oxide. In addition to reducing Co or a Co-based alloy, the annular layer composed of aggregates mainly composed of the above composite oxide is replaced with an annular layer composed mainly of fine oxide hard particles mainly composed of oxides of the above oxidizing elements. A method for producing a Co-based alloy powder, characterized in that: (5) Production of the Co-based alloy powder according to claim (4), wherein the oxidizing element is an element that forms a solid solution with Co and has a greater affinity for oxygen than Co. Method. (6) The oxidizing element is Al, Si, Ti, V, Cr
, W, Hf, Be, Nb, and Zr. , W, Hf, Be, Nb, and Zr. (7) The method for producing a Co-based alloy powder according to claim (4), wherein the oxidation treatment is performed while fluidizing the Co-based alloy powder material.