JP7069800B2 - Hard particle powder for sintered body - Google Patents

Description

The present invention relates to a hard particle powder for a sintered body, and more particularly, it is a hard particle powder to which REM is added, which is excellent in powder characteristics and sintering characteristics, and a sintered body (sintered body) using the same. For example, the present invention relates to a hard particle powder for a sintered body, which can obtain high wear resistance when a car engine valve seat) is manufactured.

Trivalois (registered trademark) T-400 is well known as hard particles having a high wear resistance of Co groups forming a hard phase mainly composed of Mo silice. Co-2.5Si-28Mo-8.5Cr-based alloy powder, which is equivalent to Trivalois (registered trademark) T-400, greatly improves the wear resistance of automobile engine valve seats (hereinafter simply referred to as "valve seats"). As a contributing hard particle, it is often used in automobile engines that are subject to high loads. Therefore, many prior arts have been proposed.

For example, Patent Document 1 aims to disperse a larger amount of a hard layer in a substrate without impairing wear resistance, strength, and the like.
(A) Abrasion-resistant firing in which a raw material powder containing a matrix-forming powder (iron, SUS316, SUS304, SUS310, SUS430) and a hard layer-forming powder (Co-28Mo-2.5Si-8Cr) is compression-molded and sintered. In the method of manufacturing the connecting member
(B) A method for manufacturing a wear-resistant sintered member in which 90% by mass or more of the matrix-forming powder is a fine powder having a maximum particle size of 46 μm and the ratio of the hard layer-forming powder to the raw material powder is 40 to 70% by mass. It has been disclosed.

Further, in Patent Document 2, for the purpose of obtaining an iron-based sintered alloy material having excellent wear resistance,
(A) 100 weight of iron-based alloy powder composed of pure iron powder, alloy iron powder, carbon powder, fine carbide-precipitated steel powder, and hard particle powder (Cr-Mo-Co-based, Ni-Cr-Mo-Co-based, etc.) 0.2 to 3.0 parts by weight of solid lubricant powder (sulfide, fluoride) and / or 0.2 to 5.0 parts by weight of oxide stabilized powder (oxide of rare earth element). The iron-based alloy powder to which Y ₂ O ₃ , CeO ₂ , CaTIO ₃ ) was added was compression-molded.
(B) Next, a method for manufacturing a wear-resistant iron-based alloy material for a valve seat to obtain a sintered body by sintering is disclosed.

However, as the load of engine required characteristics increases, valve seat materials are required to have higher wear resistance. Therefore, the hard particles disclosed in Patent Documents 1 and 2 have a problem that the wear resistance required for the valve seat material is not sufficient. Further, if an attempt is made to improve the wear resistance required for the valve seat material, it is considered that the powder characteristics (moldability) and the sintering characteristics are impaired. Therefore, there is a demand for a technique for improving the wear resistance required for a valve seat material without impairing the powder characteristics and the sintering characteristics.

Furthermore, in recent years, in order to respond to global social problems such as CO ₂ reduction and depletion of petroleum resources, fuel-saving lean-burn combustion technologies such as direct injection engines and premixed compression ignition (HCCI) engines, and fossil fuels are not used. A plant-based biomethanol fuel engine is being promoted.
In a lean-burn combustion engine or an alcohol fuel engine, the amount of soot during combustion is smaller than that of a conventional engine, so that the valve seat is not protected by the soot in a low temperature state after the engine is started, and there is a concern that wear will increase.

Japanese Unexamined Patent Publication No. 2007-107034 Japanese Patent Application Laid-Open No. 2003-193173

The problem to be solved by the present invention is the hard particles added to the sintered body, which can improve the wear resistance of the sintered body without impairing the powder characteristics and the sintered characteristics. The purpose is to provide a hard particle powder for a body.

In order to solve the above problems, the hard particle powder for a sintered body according to the present invention is
0.01 ≤ C ≤ 3.5 mass%,
0.5 ≤ Si ≤ 4.0 mass%,
4.0 ≤ Mn ≤ 10.0 mass%,
27.0 ≤ Ni ≤ 35.0 mass%,
0.1 ≤ Cr ≤ 40.0 mass%,
5.0 ≤ Mo ≤ 50.0 mass%,
0.1 ≤ Fe ≤ 30.0 mass%, and 0.01 ≤ REM ≤ 0.5 mass%
The gist is that the balance is composed of Co and unavoidable impurities.

By optimizing the components of Co-based hard particles containing REM, the wear resistance of the sintered body containing the hard particles can be improved without impairing the powder characteristics and the sintering characteristics. It is considered that this is because an oxide film is formed on the surface of the sintered body in a low temperature range of about 600 ° C. by adding an appropriate amount of REM to the hard particles, and this oxide film exhibits a lubricating action.

It is sectional drawing which shows the outline of the valve seat single-unit wear tester. It is a figure for demonstrating the measurement point of the wear amount of the wear test piece. It is a figure which shows the relationship between the weight increase and the temperature of the hard particle powder obtained in Reference Example 2 and Comparative Example 13.

Hereinafter, an embodiment of the present invention will be described in detail.
[1. Hard particle powder for sintered body]
The sintered hard particle powder according to the present invention contains the following elements, and the balance consists of Co and unavoidable impurities. The types of additive elements, their component ranges, and the reasons for their limitation are as follows.

(1) 0.01 ≤ C ≤ 3.5 mass%:
When the C content becomes excessive, the toughness decreases due to the formation of carbides. Therefore, the C content needs to be 3.5 mass% or less. The C content is preferably 2.0 mass% or less.
On the other hand, even if the C content is reduced more than necessary, there is no difference in the effect and there is no actual benefit. Therefore, the C content needs to be 0.01 mass% or more. The C content is preferably 0.5 mass% or more.

(2) 0.5 ≤ Si ≤ 4.0 mass%:
Si is a component element contained for the purpose of improving hardness by forming silicide. If the Si content is too low, the hardness will be too low and it will not function as hard particles. Therefore, the Si content needs to be 0.5 mass% or more. The Si content is preferably 0.8 mass% or more.
On the other hand, if the Si content is excessive, the hardness becomes too high. As a result, the hard particles are cracked and fall off from the sintered body containing the hard particles, and the amount of wear of the sintered body is rather large. Therefore, the Si content needs to be 4.0 mass% or less. The Si content is preferably 3.0 mass% or less.

(3) 0.1 ≤ Mn ≤ 10.0 mass%:
If the Mn content is too small, an oxide film is less likely to be formed on the surface of the powder, and the lubricity is lowered. As a result, wear resistance deteriorates. Therefore, the Mn content needs to be 0.1 mass% or more. The Mn content is preferably 0.2 mass% or more, more preferably 4.0 mass% or more.
On the other hand, when the Mn content becomes excessive, the sintering characteristics deteriorate due to the increase in the amount of powder oxidation. Therefore, the Mn content needs to be 10.0 mass% or less. The Mn content is preferably 7.0 mass% or less.

(4) 0.1 ≤ Ni ≤ 35.0 mass%:
If the Ni content is too low, the heat resistance deteriorates and the wear resistance deteriorates. Therefore, the Ni content needs to be 0.1 mass% or more. The Ni content is preferably 0.3 mass% or more, more preferably 9.0 mass% or more.
On the other hand, when the Ni content becomes excessive, the wear resistance deteriorates due to the decrease in heat resistance. Therefore, the Ni content needs to be 35.0 mass% or less. The Ni content is preferably 30.0 mass% or less.

(5) 0.1 ≤ Cr ≤ 40.0 mass%:
Cr is an element contained for the purpose of maintaining oxidation resistance. If the Cr content is too low, the wear resistance deteriorates due to the deterioration of the oxidation resistance. Therefore, the Cr content needs to be 0.1 mass% or more. The Cr content is preferably 3.0 mass% or more.
On the other hand, when the Cr content becomes excessive, the wear resistance deteriorates due to the decrease in heat resistance. Therefore, the Cr content needs to be 40.0 mass% or less. The Cr content is preferably 30.0 mass% or less.

(6) 5.0 ≤ Mo ≤ 50.0 mass%:
Mo is a component element contained for the purpose of maintaining the hardness of powder particles. If the Mo content is too low, the wear resistance of the sintered body containing the hard particle powder becomes insufficient. Therefore, the Mo content needs to be 5.0 mass% or more. The Mo content is preferably 14.0 mass% or more.
On the other hand, when the Mo content is excessive, the hardness becomes too high. As a result, the hard particles are cracked and fall off from the sintered body containing the hard particle powder, and the amount of wear of the sintered body is rather large. Therefore, the Mo content needs to be 50.0 mass% or less. The Mo content is preferably 40.0 mass% or less.

(7) 0.1 ≤ Fe ≤ 30.0 mass%:
Fe is an element that plays a role in improving the diffusivity of hard particle powder into iron powder. If the Fe content is too low, the diffusibility to the iron powder is lowered, and the hard particle powder is likely to fall off from the sintered body containing the hard particle powder. As a result, wear resistance deteriorates. Therefore, the Fe content needs to be 0.1 mass% or more. The Fe content is preferably 2.0 mass% or more.
On the other hand, when the Fe content becomes excessive, the Co content decreases. Since Fe has lower heat resistance and wear resistance than Co, if the Fe content is excessive, the heat resistance and wear resistance are significantly lowered. Therefore, the Fe content needs to be 30.0 mass% or less. The Fe content is preferably 20.0 mass% or less.

(8) 0.01 ≤ REM ≤ 0.5 mass%:
In the present invention, "REM" includes those containing at least one kind of lanthanoid element. REM is a component element contained in order to improve the wear resistance of the sintered body containing the hard particle powder without impairing the powder characteristics and the sintering characteristics. If the REM content is too low, it hardly contributes to the improvement of the wear resistance of the sintered body. Therefore, the REM content needs to be 0.01 mass% or more. The REM content is preferably 0.05 mass% or more.
On the other hand, when the REM content becomes excessive, the sintering characteristics deteriorate due to the increase in the amount of powder oxidation, and the wear resistance also deteriorates. Therefore, the REM content needs to be 0.5 mass% or less. The REM content is preferably 0.3 mass% or less.

[2. Manufacturing method of sintered body]
The sintered body containing the hard particle powder for a sintered body according to the present invention is
(A) The hard particle powder for a sintered body according to the present invention, pure iron powder, and graphite powder are mixed.
(B) The mixed powder is compacted to obtain a compact.
(C) It can be produced by sintering a green compact.

[2.1. Mixing process]
First, the hard particle powder for a sintered body according to the present invention (hereinafter, also simply referred to as “hard particle powder”), pure iron powder, and graphite powder are mixed (mixing step). As for the blending amount of each component, it is preferable to select the optimum blending amount according to the purpose. Further, in order to improve the moldability, it is preferable to add a molding lubricant to the raw material.

If the amount of the hard particle powder is too small, the wear resistance of the sintered body is lowered. Therefore, the blending amount of the hard particle powder is preferably 5.0 mass% or more. The blending amount of the hard particle powder is preferably 10.0 mass% or more.
On the other hand, if the blending amount of the hard particle powder becomes excessive, the sintering characteristics deteriorate. Therefore, the blending amount of the hard particle powder is preferably 50.0 mass% or less. The blending amount of the hard particle powder is preferably 30.0 mass% or less.

If the blending amount of the graphite powder is too small, the wear resistance of the sintered body is lowered. Therefore, the blending amount of the graphite powder is preferably 0.5 mass% or more. The blending amount of the graphite powder is preferably 0.8 mass% or more.
On the other hand, if the blending amount of the graphite powder is excessive, the sintering characteristics are deteriorated. Therefore, the blending amount of the graphite powder is preferably 2.0 mass% or less. The blending amount of the graphite powder is preferably 1.5 mass% or less.

[2.2. Molding process]
Next, the mixed powder is compacted to obtain a compact. The molding conditions are not particularly limited, and the optimum conditions can be selected according to the purpose. Generally, the higher the molding pressure, the higher the molding density. After molding, the green compact is calcined in the air to degreas.

[2.3. Sintering process]
Next, the green compact is sintered (sintering step).
As the sintering conditions, it is preferable to select the optimum conditions according to the composition of the green compact. Generally, the higher the sintering temperature, the denser the sintered body can be obtained by heat treatment for a short time. On the other hand, if the sintering temperature becomes too high, there is a problem that the hard particles diffuse too much into the iron-based matrix or melt. The optimum sintering conditions vary depending on the composition of the green compact, but it is usually preferable to sinter at 1100 ° C to 1300 ° C for 0.5 hours to 3 hours. Further, the sintering is preferably performed in a reducing atmosphere (for example, in a decomposed ammonia atmosphere).

[3. Action]
By optimizing the components of Co-based hard particles containing REM, the wear resistance of the sintered body containing the hard particles can be improved without impairing the powder characteristics and the sintering characteristics. It is considered that this is because an oxide film is formed on the surface of the sintered body in a low temperature range of about 600 ° C. by adding an appropriate amount of REM to the hard particles, and this oxide film exhibits a lubricating action.

( Reference Examples 1 to 16, Examples 17 to 18, Reference Examples 19 to 30, Comparative Examples 1 to 44)
[1. Preparation of sample]
[1.1. Preparation of hard particle powder]
The raw materials were blended so as to have the compositions shown in Tables 1 and 2. The raw material mixture was dissolved and a hard particle powder was obtained by an atomizing method. Tables 1 and 2 also show the sintering density of the sintered body containing the hard particle powder and the amount of wear of the sintered body when the wear resistance test described later was performed.

[1.2. Fabrication of sintered body]
Pure iron powder (ASC100.29) 69.2 mass%, hard particle powder 30 mass%, and graphite powder (CPB) 0.8 mass% were blended. This was taken as 100 parts by weight, and 0.5 part by weight of Zn—St (molding lubricant) was further added and mixed.
Next, the raw material was compression molded at a molding pressure of 8 t / cm ² . The green compact shape is
(A) Disc shape with a diameter of 35 mm and a thickness of 14 mm, or
(B) A ring shape having an outer diameter of 28 mm, an inner diameter of 20 mm, and a thickness of 4 mm was formed.
Next, the green compact was degreased at 400 ° C. for 1 hour in the air atmosphere. Further, the degreased body was sintered at 1160 ° C. for 1 hour in a decomposed ammonia atmosphere (N ₂ + 3H ₂ ) to obtain a sintered body.

[2. Test method]
[2.1. Powder characteristics]
The powder characteristics (particle size distribution, apparent density, fluidity, powder hardness, oxidation start temperature) of the obtained hard particle powder were investigated. here,
(A) Particle size distribution is based on Japanese Industrial Standards: JIS Z 2510-2004.
(B) The apparent density is based on the Japanese Industrial Standards: JIS Z 2504-2012.
(C) The fluidity is determined according to the Japanese Industrial Standards: JIS Z 2502-2012.
(D) The powder hardness is determined by a micro hardness measuring machine.
(E) The oxidation start temperature was measured by a thermal balance.

[2.2. Molding and sintering properties]
The molding properties and sintering characteristics (compact density, sintering density, chemical composition, sintered body hardness, and crimp strength) of the prepared powder compacts and sintered body were investigated.
Here, the powder density and the sintering density were measured according to the Japanese Industrial Standards: JIS Z 2508 and JIS Z 2509-2004. The chemical composition was determined by the infrared absorption method.
Sintered body hardness (HRA) was measured by a Rockwell hardness tester. The pressure ring strength was measured by an Amsler tester using a ring-shaped sintered body.

[2.3. Abrasion resistance test of sintered body]
The wear resistance test of the sintered body was performed using the valve seat single-unit wear tester shown in FIG. 1 (hereinafter, also simply referred to as “wear tester”). A disk-shaped sintered body (diameter 35 mm × thickness 14 mm) was processed into a valve seat shape, and this was used as each wear test piece. Then, the wear test piece was press-fitted into the seat holder and set in the wear tester.
The wear tester was driven under the test conditions shown in Table 3, and the wear test piece was indirectly heated by heating the valve with a gas flame, while the wear test piece was worn by the tapping input by the crank drive.

The shape of the wear test piece before and after the wear test was measured using a shape measuring instrument. As shown in FIG. 2 (enlarged view of the portion indicated by the arrow A in FIG. 1), the difference D in the direction perpendicular to the wear test piece surface was obtained, and this was used as the wear amount of the wear test piece.

[3. result]
[3.1. Powder characteristics]
Table 4 shows the powder characteristics of the hard particle powders obtained in Reference Examples 1 to 3 and Comparative Examples 9 to 10. FIG. 3 shows the relationship between the weight increase and the temperature of the hard particle powders obtained in Reference Example 2 and Comparative Example 13. From Table 4 and FIG. 3, the following can be seen.
(1) The particle size distribution and powder characteristics of Reference Examples 1 to 3 were almost the same as the particle size distribution and powder characteristics of Comparative Examples 9 to 10.
(2) Regarding the particle size distributions of Reference Examples 1 to 3 and Comparative Examples 9 to 10, there is little difference in the particle size distributions between -100 to +145 mesh and -145 to +200 mesh, which is considered to be due to variations during powder production.
(3) The hardness of Reference Examples 1 to 3 was almost the same as that of Comparative Examples 9 to 10.
(4) Reference Example 2 has a lower oxidation start temperature than Comparative Example 13. This is because the addition of REM to the hard particle powder facilitates oxidation.

[3.2. Molding and sintering properties]
Table 5 shows the characteristics of the green compact and the sintered body obtained in Reference Examples 1 to 3 and Comparative Examples 9 to 10. From Table 5, the following can be seen.
(1) Reference Examples 1 to 3 and Comparative Examples 9 to 10 had almost the same powder density, sintered density, and sintered body hardness, although their compositions were different.
(2) Reference Examples 1 to 3 have higher ring strength than Comparative Examples 9 to 10. Since the annulus strength is due to the hardness of the sintered body, the higher the hardness of the sintered body, the higher the annulus strength tends to be.

[3.3. Wear resistance test]
Tables 1 and 2 show the composition of each hard particle powder, the sintering density of the sintered body using the hard particle powder, and the amount of wear of the sintered body during the wear resistance test. The following can be seen from Tables 1 and 2.
(1) In Reference Examples 1 to 16, Examples 17 to 18, and Reference Examples 19 to 30 , the amount of wear was less than 20 μm. On the other hand, in all of Comparative Examples 1 to 44, the amount of wear was 20 μm or more. That is, in Reference Examples 1 to 16, Examples 17 to 18, and Reference Examples 19 to 30 , the amount of wear was smaller than that in Comparative Examples 1 to 44.

(2) Comparing Reference Examples 1 to 16, Examples 17 to 18, Reference Examples 19 to 30 and Comparative Examples 13 to 28, all of them satisfy the preferable component range of the present invention except for the presence or absence of REM. .. Therefore, in the component compositions (excluding REM) according to Reference Examples 1 to 16, Examples 17 to 18, and Reference Examples 19 to 30 , the addition of REM has the effect of improving the wear resistance of the sintered body (valve seat). It turned out that there is.
(3) As shown in Comparative Examples 29 to 44, it can be seen that if the content of REM is too large, the effect of improving the wear resistance of the sintered body (valve seat) cannot be obtained. From these facts, it can be seen that the REM content should not exceed 0.6 mass%. From this, it was found that the REM content was preferably 0.5 mass% or less, more preferably 0.25 mass% or less.

(4) Comparative Example 1 has a large amount of wear. It is considered that this is because the amount of C is too large, the hardness becomes too high, and the hard particle powder is crushed.
(5) Comparative Example 2 has a large amount of wear. It is considered that this is because the amount of Si is too large, the hardness becomes too high, and the hard particle powder falls off.
(6) Comparative Example 3 has a large amount of wear. It is considered that this is because the powder oxide film was not formed because Mn was not contained, and the lubricity was deteriorated.
(7) Comparative Example 4 has a large amount of wear. It is considered that this is because the amount of Mn is large, the amount of powder oxidation increases, and the sintering characteristics deteriorate.
(8) Comparative Example 5 has a large amount of wear. It is considered that this is because the heat resistance is lowered because it does not contain Ni.
(9) Comparative Example 6 has a large amount of wear. It is considered that this is because the amount of Ni is too large, and on the contrary, the balance element Co is reduced, and the heat resistance and wear resistance are lowered.

(10) Comparative Example 7 has a large amount of wear. It is considered that this is because the heat resistance is lowered because it does not contain Cr.
(11) Comparative Example 8 has a large amount of wear. It is considered that this is because the amount of Cr is too large, so that the balance element Co is conversely reduced, and the heat resistance and wear resistance are lowered.
(12) Comparative Example 9 has a large amount of wear. It is considered that this is because the amount of Mo is too small, so that the hardness is lowered and the wear resistance is lowered.
(13) Comparative Example 10 has a large amount of wear. It is considered that this is because the amount of Mo is too large, the hardness becomes too high, and the hard particle powder falls off.
(14) Comparative Example 11 has a large amount of wear. It is considered that this is because the diffusibility to the iron powder is lowered because Fe is not contained, and the hard particle powder is easily dropped off.
(15) Comparative Example 12 has a large amount of wear. It is considered that this is because the heat resistance is lowered because the amount of Fe is too large.

(16) Comparative Examples 13 to 28 have a large amount of wear. It is considered that this is because oxidation at a low temperature does not occur because REM is not contained, and the lubricity on the valve surface is lowered.
(17) Comparative Examples 29 to 44 have a large amount of wear. It is considered that this is because the amount of REM oxidation is large, the amount of powder oxidation is increased, and the sintering characteristics are deteriorated.

From the above, when REM is added to a hard particle powder composed of a predetermined component system, the wear resistance of the sintered body (valve seat) can be improved with almost no loss of powder characteristics and sintering characteristics. It was also found that a sintered body having excellent wear resistance can be obtained.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

The hard particle powder for a sintered body according to the present invention is used as a hard particle powder added for the purpose of improving wear resistance to various sintered bodies used as valve seats, valve guides, and other mechanical structural parts. be able to.

Claims (2)

0.01 ≤ C ≤ 3.5 mass%,
0.5 ≤ Si ≤ 4.0 mass%,
4.0 ≤ Mn ≤ 10.0 mass%,
27.0 ≤ Ni ≤ 35.0 mass%,
0.1 ≤ Cr ≤ 40.0 mass%,
5.0 ≤ Mo ≤ 50.0 mass%,
0.1 ≤ Fe ≤ 30.0 mass%, and 0.01 ≤ REM ≤ 0.5 mass%
Hard particle powder for sintered body containing Co and the balance consisting of Co and unavoidable impurities. The hard particle powder for a sintered body according to claim 1, wherein 4.0 ≤ Mn ≤ 7.0 mass%.

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