JPH0533100A - Production of alloy series sintered body - Google Patents

Abstract

PURPOSE:To easily obtain an alloy series sintered body, e.g. as mechanism parts sufficiently coated with an alumina layer having good adhesion in spite of the shape of the parts and excellent in mechanical properties such as toughness and hardness with good dimensional accuracy. CONSTITUTION:A green compact obtd. by compacting mixed powder of, by weight, 70 to 90% Fe-Cr-Ni-Al alloy powder and the balance Fe-Cr-Al alloy powder into a prescribed shape is sintered in a nonoxidizing atmosphere and is thereafter subjected to heat treatment in an oxidizing atmosphere to precipitate alumina components on the surface, by which the alloy sintered body is manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an alloy-based sintered body, and specifically, it is made of a base material having high hardness, high strength and toughness, and has a dense surface and excellent adhesion. As a high-strength, high-wear-resistant mechanical part (for example, chuck of electric tools, rotary shaft, gear, cam, etc.) covered with excellent uniform aluminum oxide (hereinafter referred to as "alumina" as appropriate) The present invention relates to a method for manufacturing an alloy-based sintered body.

[0002]

In the case of mechanical parts such as chucks of electric tools, rotary shafts, gears, cams, and blades of hair clippers, by coating the surface with a high hardness material such as oxide, nitride, or carbide, It is known to improve wear resistance and corrosion resistance. The coating is performed by a method such as a thermal spraying method or a sputtering method.

However, in the case of coating by the thermal spraying method, it is difficult to finely control the thickness of the coating layer, the adhesion is not sufficient, and it is difficult to apply it to small parts such as high heat applied to the base material. There is a drawback that. Further, in the case of coating by sputtering, it is difficult to secure the required coating thickness.
In addition, in the case of a complicated shape, it is difficult to apply the coating uniformly on the whole, and on the other hand, in the case of a shape having a strong flatness, the adhesion of the film is not good. In order to improve the adhesion, it is necessary to perform troublesome processing such as surface roughening and formation of an undercoat layer.

Further, it is also possible to form the entire mechanical component with a ceramic sintered body. However, in the case of mechanical parts using bulk ceramic sintered bodies, the dimensional accuracy is low,
There is a problem that it does not have sufficient toughness and cracks easily.

[0005]

In view of the above circumstances, the present invention is sufficiently covered with an alumina layer having good adhesion regardless of the shape of parts, and is excellent in mechanical properties such as toughness and hardness. Another object of the present invention is to provide a useful method capable of easily obtaining an alloy-based sintered body as a mechanical component with high dimensional accuracy.

[0006]

In order to solve the above-mentioned problems, in the method for manufacturing an alloy-based sintered body according to the present invention, F
After sintering a mixed powder of e-Cr-Ni-Al alloy powder of 70 to 90 wt% and the balance of Fe-Cr-Al alloy powder into a predetermined shape, after sintering in a non-oxidizing atmosphere The alumina component is deposited on the surface by heat treatment in an oxidizing atmosphere.

The present invention will be described in detail below. First, Fe-Cr-Ni-Al alloy powder and Fe-C
r-Al alloy powders are prepared. Fe-Cr-
The Ni-Al-based alloy powder has a Cr: 2 content as defined in claim 2.
5-40 wt%, Ni: 15-25 wt%, Al: 4-8 wt%
%, Any one or more of Zr, Hf, Ce, La, Nd, and Gd: 0.05 to 1.0 wt%, Y: 0
A composition of 0.2 wt% (preferably 0.1 wt% or less) and Fe: balance is suitable. The Fe-Cr-Al-based alloy powder also has a Cr content of 15 to 20 wt.
%, Al: 2 to 4 wt%, Zr, Hf, Ce, La, N
Any one or more of d and Gd: 0.05 to
1.0 wt%, Y: 0 to 0.2 wt% (preferably 0.1 wt%
% Or less), and Fe: the composition of the balance is suitable.

For example, the raw material metals are melted in a high-frequency furnace in a ratio having the above composition and powdered by an atomizing method to produce respective alloy powders. The two kinds of alloy powder thus obtained are mixed by a mixer, and further, a binder (for example,
PVA) is added and mixed, and the mixture is molded by, for example, pressure molding. The binder may be added when mixing the two types of alloy powders. The mixing ratio of the Fe-Cr-Ni-Al-based alloy powder and the Fe-Cr-Al-based alloy powder is 70 to 90 wt% in the former case, 30 to 10 wt% in the latter case, and 70 to 80 wt% in the former case, 30 to 20 wt% in the latter case. It is set to the range of.

Considering the use for various machine parts, etc., it is preferable that the pressure applicable during molding is in a wide range from low pressure to high pressure. In the case of the present invention, 1
A low pressure of about 00 MPa can be applied, and a wide range of pressures can be applied. Usually, it is selected from a wide range of about 200 to 1000 MPa. However, the molding pressure is 100 MPa
If it is less than the above range, it tends to be difficult to obtain sufficient dimensional accuracy.

Next, the alloy powder compact is sintered by heat treatment in a non-oxidizing atmosphere (inert gas atmosphere, reducing gas atmosphere or vacuum atmosphere) at a temperature of 1300 to 1400 ° C., for example. Within this heat treatment temperature range, sufficient hardness (H
v = about 300), and a base material having sufficient strength can be obtained even for mechanical parts.

After sintering, if necessary, it is processed into a predetermined shape before forming the alumina layer (coating). Since it is before forming the alumina layer, it can be easily processed. Since it is not the one obtained by sintering the ceramic powder but the one obtained by sintering the above alloy powder, it is not chipped or cracked as in the case where the ceramic powder is sintered. After being formed into a predetermined shape, the sintered body is heat-treated in an oxidizing atmosphere (for example, in the air or an oxidizing gas atmosphere) at a temperature exceeding 1000 ° C., for example. By this heat treatment, aluminum oxide is deposited on the surface and an alloy-based sintered body with an alumina layer is completed.

Although it is possible to obtain an alloy-based sintered body with an alumina layer by using only one of the two types of alloy powders, the following drawbacks are not practical. Fe-
The disadvantage of using only the Cr-Ni-Al alloy powder is that the particle hardness of the Fe-Cr-Ni-Al alloy powder is H.
This is due to the high value of v = 400, and one is
This is because a large molding pressure of 5 ton / cm ² is required, and it is difficult to manufacture due to a large restriction. Another reason is that it is usually necessary to process after molding and sintering. Is hard and difficult to post-process. If post-processing after sintering is difficult, it is not feasible to manufacture parts with high dimensional accuracy.

On the contrary, the disadvantage of using only the Fe-Cr-Al alloy powder is that the particle hardness of the Fe-Cr-Al alloy powder after annealing is as soft as Hv = 170. Although the molding pressure and the difficulty of post-processing are eliminated, it is difficult to secure sufficient base metal hardness and it is not possible to realize an appropriate mechanical component.

[0014]

In the alloy-based sintered body according to the manufacturing method of the present invention, Al, which is one of the alloy compositions, forms an alumina layer on the surface layer by heat treatment in an oxidizing atmosphere. It is formed in a state of being rooted in the alloy filling the inside, which has the function of increasing the adhesion between the surface layer and the alloy, and of course Hv = 2000 on the surface.
Precipitation of a certain amount of alumina serves to increase the surface hardness. Of course, the alloy filling the interior of the alloy-based sintered body acts to enhance the toughness of the sintered body. Moreover, 5-1
An alumina layer having a thickness of about 0 μm can be formed by a heat treatment for a short time, and a thickness of 10 to 20 μm can be sufficiently obtained, so that good abrasion resistance can be easily ensured.

Then, the apparent powder hardness as a whole is moderated by adding an appropriate amount of the Fe-Cr-Al alloy powder, and as a result, it is possible to apply from a low pressure at the time of molding to a fine metal shape. Since it can also be used for mold forming (improving moldability), there are fewer restrictions on manufacturing, and since the deformation caused by sintering can be easily corrected by cutting or grinding, it is possible to obtain one with good dimensional accuracy. It will be easy to make.

Since Fe-Cr-Ni-Al based alloy powder is secured as a main component in an amount of 70 wt% or more, the hardness is more than necessary compared with the case where the whole is Fe-Cr-Ni-Al based alloy powder. There is no fear that it will decrease.

[0017]

Embodiments of the present invention will be described below. Of course,
This invention is not limited to the following embodiments. -Example 1-Cr: 31 wt%, Ni: 21 wt%, Al: 6 wt%, Y:
The raw material metal was melted in a high-frequency melting furnace at a ratio of 0.1 wt% and balance: Fe, and Fe-Cr-Ni-Al alloy powder having 350 mesh or less was obtained by an atomizing method.

Separately, similarly, Cr: 18 wt%, A
The raw material metal was melted in a high-frequency melting furnace at a ratio of l: 3 wt%, Zr: 0.2 wt%, and the balance: Fe, and Fe-Cr-Al alloy powder of 350 mesh or less was obtained by an atomizing method. And Fe-Cr-Ni-Al alloy powder and F
The e-Cr-Al alloy powder was thoroughly mixed with a mixer at a ratio of 90 wt% for the former and 10 wt% for the latter to obtain a mixed powder.

PVA for a binder was added to and mixed with the mixed powder thus obtained, and molded at a pressure of 200 MPa. Then, the formed body is vacuumed at 1350 ° C. for 3 minutes.
After heat treatment for a long time, the powder was sintered and then ground to be accurately adjusted to a predetermined shape. In the grinding process, it was easier to process than a sintered body containing only Fe-Cr-Ni-Al alloy powder, and could be easily formed into a predetermined shape.

Then, in air, at 1150 ° C., 2
An alumina layer was formed by heat treatment for 0 hours and heat treatment at 1250 ° C. for 30 minutes, followed by air cooling to obtain an alloy-based sintered body. Examples 2 to 6-Each composition of the Fe-Cr-Ni-Al alloy powder and Fe-Cr-Al alloy powder, and the mixing ratio of both alloy powders are as shown in Table 1, respectively, An alloy-based sintered body was obtained in the same manner as in Example 1.

-Comparative Example 1- An alloy-based sintered body was prepared in the same manner as in Example 1 except that only Fe-Cr-Ni-Al alloy powder was used in Example 1 and the pressure during molding was 500 MPa. Obtained. -Comparative Example 2- An alloy-based sintered body was obtained in the same manner as in Example 1 except that only Fe-Cr-Al-based alloy powder was used in Example 1.

-Comparative Example 3- Spatter on the surface of martensitic stainless steel for blades
To form a ZrN film. Hardened ZrN powder
Target is Ar gas, 10^-2-10 ^-3Torr
Stainless steel surface by high frequency sputtering in atmosphere
And a thickness of about 0.5 μm. Substrate temperature is about 200 ℃
And

-Comparative Example 4-The surface of martensitic stainless steel for blades was roughened by shot blasting to give irregularities of about 10 μm. Then, on the roughened surface of stainless steel, alumina particles having a particle diameter of about 30 μm were sprayed by plasma spraying. The thickness of the alumina layer is about 50 μm.

[0024]

[Table 1]

For the examples and comparative examples, the adhesion of the coating such as the alumina layer, the hardness of the base material, the workability after sintering, and the wear resistance were examined. The results are shown in Table 2. In addition, ○ and × in Table 2 are as follows. Adhesion of coating- ○: 150 g steel ball dropped from a height of 1 m without film cracking ×: 150 g steel ball dropped from a height of 1 m and film cracking Workability after sintering- ○: Easy to grind ×: Difficult to grind Abrasion resistance − ○: The base is not exposed even if the surface is rubbed with a diamond file for 1 minute. ×: The base is exposed when the surface is rubbed with a diamond file for 1 minute. In the alloy-based sintered body, the alumina layer has a thickness of 5
It was confirmed by microscopic observation that the base material was formed to have a root-like shape with a thickness of 10 μm. Further, the dimensions of the alloy-based sintered body were measured and it was confirmed that the sintered body was finished with high dimensional accuracy.

[0026]

[Table 2]

As shown in Table 2, the alloy-based sintered bodies of the examples have good adhesion of the alumina layer, workability after sintering, and wear resistance, and the matrix filling the inside of the sintered body is good. Material hardness is also Hv =
The hardness was about 500, which was a sufficient hardness. On the other hand, in Comparative Example 1, the workability after sintering was inferior to that of the Example and required a high molding pressure, and in Comparative Example 2, the base material hardness was much inferior to that of the Example, and the practicality of each was not sufficient. Met. Further, as seen in Comparative Examples 3 and 4, the coating by the sputtering method or the thermal spraying method does not form a film with good adhesion, and in Comparative Example 3, the abrasion resistance is not sufficient.

[0028]

As described above, in the method for manufacturing an alloy-based sintered body according to the present invention, Fe-Cr-Ni-Al is used.
The Fe-Cr-Al alloy powder is mixed with an appropriate amount of the Fe-Cr-Al alloy powder to sinter a powder compact, which is then subjected to an oxidation treatment. A large, sufficiently thick alumina layer is deposited and the interior is filled with alloy, so wear resistance, toughness,
It has excellent mechanical properties such as hardness. Moreover, even during the manufacturing process, the apparent powder hardness is moderated moderately, and the moldability is improved, so it is easy to manufacture and baked. The method of the present invention is very useful because the dimensional accuracy can be easily improved by post-workability after binding.

In addition, the composition of each alloy powder is appropriate, so that the invention of claim 2 has an advantage that it is possible to surely obtain those having good mechanical properties such as wear resistance, toughness, and hardness. .

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[Procedure amendment]

[Submission date] November 9, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

Although it is possible to obtain an alloy-based sintered body with an alumina layer by using only one of the two types of alloy powders, the following drawbacks are not practical. Fe-
The disadvantage of using only the Cr-Ni-Al alloy powder is that the particle hardness of the Fe-Cr-Ni-Al alloy powder is H.
This is due to the high value of v = 400, and one is
This is because a large molding pressure of 500 MPa is required and it is difficult to manufacture due to a large restriction. Another reason is that it is usually necessary to process after molding and sintering, but since the base material is hard , This is because processing is difficult. If post-processing after sintering is difficult, it is not feasible to manufacture parts with high dimensional accuracy.

Claims (2)

[Claims] 1. Fe-Cr-Ni-Al alloy powder is 7
The surface of the compact is formed by molding a mixed powder of 0 to 90 wt% and the rest of Fe-Cr-Al alloy powder into a predetermined shape, sintering the mixture in a non-oxidizing atmosphere, and then heat-treating it in an oxidizing atmosphere. A method for producing an alloy-based sintered body, in which an alumina component is precipitated. 2. The Fe-Cr-Ni-Al alloy is C
r: 25-40 wt%, Ni: 15-25 wt%, Al: 4
-8 wt%, any one or more of Zr, Hf, Ce, La, Nd, and Gd: 0.05-1.0 wt%,
Y: 0 to 0.2 wt%, Fe: balance, Fe-Cr
-Al-based alloy is Cr: 15 to 20 wt%, Al: 2 to 4
wt%, any one or more of Zr, Hf, Ce, La, Nd, and Gd: 0.05 to 1.0 wt%, Y: 0
The method for producing an alloy-based sintered body according to claim 1, wherein the alloy-based sintered body is composed of ˜0.2 wt% and Fe: balance.