CN110153405B

CN110153405B - Hard particle powder for sintered body

Info

Publication number: CN110153405B
Application number: CN201910112970.3A
Authority: CN
Inventors: 长濑石根; 山本知己; 远藤隆久; 河野俊介; 服部广基
Original assignee: Daido Steel Co Ltd
Current assignee: Daido Steel Co Ltd
Priority date: 2018-02-16
Filing date: 2019-02-13
Publication date: 2022-02-08
Anticipated expiration: 2039-02-13
Also published as: US20190256955A1; KR20190099141A; JP2019143176A; CN110153405A; JP7069800B2

Abstract

The present invention provides a hard particle powder for a sintered body, which is composed of: c is more than or equal to 0.01 and less than or equal to 3.5 percent by mass, Si is more than or equal to 0.5 and less than or equal to 4.0 percent by mass, Mn is more than or equal to 0.1 and less than or equal to 10.0 percent by mass, Ni is more than or equal to 0.1 and less than or equal to 35.0 percent by mass, Cr is more than or equal to 0.1 and less than or equal to 40.0 percent by mass, Mo is more than or equal to 5.0 and less than or equal to 50.0 percent by mass, Fe is more than or equal to 0.1 and less than or equal to 30.0 percent by mass, REM is more than or equal to 0.01 and less than or equal to 0.5 percent by mass, and the balance is Co and inevitable impurities. A sintered body comprising a hard particle powder, a pure iron powder and a graphite powder is also provided.

Description

Hard particle powder for sintered body

Technical Field

The present invention relates to a hard particle powder for a sintered body. More particularly, the present invention relates to a hard particle powder to which a Rare Earth Metal (REM) is added, which is excellent in powder characteristics or sintering characteristics, and can achieve high wear resistance when a sintered body (e.g., an automobile engine valve seat) is manufactured by using the hard particle powder.

Background

As is well known, TRIBALOY (registered trademark) T-400 is a Co-based hard particle having high wear resistance and forming a hard phase mainly containing molybdenum silicide. Co-2.5Si-28Mo-8.5 Cr-based alloy powder, which is an equivalent material of TRIBALOY (registered trademark) T-400, is often used as hard particles that significantly contribute to improvement in wear resistance of a valve seat for an automobile engine (hereinafter, simply referred to as "valve seat") in an automobile engine to which a high load is applied. Therefore, many prior arts have been proposed.

For example, patent document 1 discloses a method for producing a wear-resistant sintered member, which aims to disperse a large amount of a hard layer in a matrix without impairing wear resistance, strength, and the like. The method includes press-forming a raw material powder containing a matrix-forming powder (iron, SUS316, SUS304, SUS310, or SUS430) and a hard layer-forming powder (Co-28Mo-2.5Si-8Cr), and sintering. The method is characterized in that 90 mass% or more of the matrix-forming powder is a fine powder having a maximum particle diameter of 46 μm, and the proportion of the hard layer-forming powder in the raw material powder is 40 to 70 mass%.

Further, patent document 2 discloses a method of manufacturing a wear-resistant iron-based alloy material for a valve seat, aiming at obtaining an iron-based sintered alloy material having excellent wear resistance. The method comprises (a) stabilizing a powder (Y) by adding 0.2 to 3.0 parts by weight of a solid lubricating material powder (sulfide or fluoride) and/or 0.2 to 5.0 parts by weight of an oxide₂O₃、CeO₂Or CaTiO₃An oxide of a rare earth element) to 100 parts by weight of an iron-based alloy powder comprising a pure iron powder, an iron alloy powder, a carbon powder, a steel powder precipitated with fine carbides, and a hard particle powder (Cr-Mo-Co based powder, Ni-Cr-Mo-Co based powder, etc.) to obtain an iron-based alloy powder, and press-forming the iron-based alloy powder; and (b) sintering to obtain a sintered body.

However, in response to an increase in load of the required characteristics of the engine, a valve seat material is required to have higher wear resistance. Therefore, there are problems as follows: the hard particles disclosed in

patent documents

1, 2, etc. cannot sufficiently satisfy the wear resistance required for the valve seat material. Further, it is considered that attempts to improve the wear resistance required for the valve seat material may impair the powder characteristics (formability) or the sintering characteristics. Therefore, there is a need for a technique for improving the wear resistance required for a valve seat material without impairing the powder characteristics and the sintering characteristics.

Further, in recent years, in order to cope with global-scale social problems such as carbon dioxide emission reduction and exhaustion of petroleum resources, fuel-saving lean-burn combustion technologies such as direct injection engines and Homogeneous Charge Compression Ignition (HCCI) engines and bioethanol fuel engines using plant raw materials without using fossil fuels have been promoted.

Lean burn engines or alcohol-fueled engines produce only a small amount of smoke during combustion as compared to conventional engines. Therefore, there is a concern that smoke cannot protect the valve seat in a low temperature state after the engine ignition, and thus may be easily worn.

Patent document 1: JP-A2007-107034

Patent document 2: JP-A2003-

Disclosure of Invention

An object that the present invention has attempted to achieve is to provide a hard particle powder for a sintered body, which is a hard particle added to a raw material powder of the sintered body and is capable of improving wear resistance of the sintered body without impairing powder characteristics and sintering characteristics.

In order to achieve the above object, a hard particle powder for a sintered body according to the present invention comprises:

c is more than or equal to 0.01 percent and less than or equal to 3.5 percent by mass,

si is more than or equal to 0.5 percent and less than or equal to 4.0 percent by mass,

mn is more than or equal to 0.1 percent and less than or equal to 10.0 percent by mass,

ni is more than or equal to 0.1 percent and less than or equal to 35.0 percent by mass,

cr is between 0.1 and 40.0 percent by mass,

mo is more than or equal to 5.0 percent and less than or equal to 50.0 percent by mass,

0.1 to 30.0 mass% of Fe, and

REM is more than or equal to 0.01 percent and less than or equal to 0.5 percent by mass,

the balance being Co and unavoidable impurities.

The present inventors have found that when the components in the REM-containing Co-based hard particles are optimized, the wear resistance of the sintered body containing hard particles can be improved without impairing the powder characteristics and sintering characteristics. It is considered that this is because, when an appropriate amount of REM is added to the hard particles, an oxide coating is generated on the surface of the sintered body in a low temperature range of about 600 ℃, and the oxide coating exhibits a lubricating effect.

Drawings

Fig. 1 is a cross-sectional view showing an outline of a wear tester for a single valve seat.

Fig. 2 is a view showing a measurement position for describing a wear amount of the wear test specimen.

Fig. 3 is a view showing the relationship between the temperature and the weight increase of the hard particle powders obtained in example 2 and comparative example 13.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail.

1. Hard particle powder for sintered body

The hard particle powder for a sintered body according to the present invention includes elements as described below, and the balance is Co and inevitable impurities. The kinds of the constituent elements, the content ranges thereof, and the reasons for limitation are as follows.

(1) C is more than or equal to 0.01 and less than or equal to 3.5 percent by mass:

when the C content is too large, the toughness is lowered due to the generation of carbides. Therefore, the content of C in the hard particle powder for a sintered body needs to be 3.5 mass% or less. The content of C is preferably 2.0 mass% or less.

On the other hand, the reduction in C content is more than necessary, there is no difference in effect, and no practical benefit is produced. Therefore, the content of C in the hard particle powder for a sintered body needs to be 0.01 mass% or more. The content of C is preferably 0.5 mass% or more.

(2) Si is more than or equal to 0.5 mass percent and less than or equal to 4.0 mass percent:

si is a component element added for forming silicide to increase hardness. In the case where the Si content is too small, the hardness becomes too poor, and the hard particle powder cannot function as hard particles. Therefore, the content of Si in the hard particle powder for a sintered body needs to be 0.5 mass% or more. The content of Si is preferably 0.8 mass% or more.

On the other hand, in the case where the Si content is too large, the hardness becomes too high. As a result, the hard particles are broken and fall off from the sintered body containing the hard particles, which in turn increases the amount of wear of the sintered body. Therefore, the content of Si in the hard particle powder for a sintered body needs to be 4.0 mass% or less. The content of Si is preferably 3.0 mass% or less.

(3) Mn is more than or equal to 0.1 mass% and less than or equal to 10.0 mass%:

in the case where the Mn content is too small, an oxide coating is not easily generated on the surface of the powder, resulting in a decrease in the lubricating property. As a result, wear resistance deteriorates. Therefore, the content of Mn needs to be 0.1 mass% or more in the hard particle powder for the sintered body. The content of Mn is preferably 0.2 mass% or more, and more preferably 4.0 mass% or more.

On the other hand, in the case where the Mn content is too large, sintering characteristics are deteriorated due to an increase in the amount of powder oxidation. In the hard particle powder for a sintered body, the content of Mn needs to be 10.0 mass% or less. The content of Mn is preferably 7.0 mass% or less.

(4) Ni is more than or equal to 0.1 mass percent and less than or equal to 35.0 mass percent:

in the case where the Ni content is too small, wear resistance is deteriorated due to a decrease in heat resistance. Therefore, the content of Ni in the hard particle powder for a sintered body needs to be 0.1 mass% or more. The content of Ni is preferably 0.3 mass% or more, and more preferably 9.0 mass% or more.

On the other hand, in the case where the Ni content is too large, wear resistance is deteriorated due to a decrease in heat resistance. Therefore, the content of Ni in the hard particle powder for a sintered body needs to be 35.0 mass% or less. The content of Ni is preferably 30.0 mass% or less.

(5)0.1 mass% or more and 40.0 mass% or less of Cr:

cr is an element added to impart oxidation resistance. In the case where the Cr content is too small, wear resistance is deteriorated due to a reduction in oxidation resistance. Therefore, the content of Cr in the hard particle powder for sintered body needs to be 0.1 mass% or more. The content of Cr is preferably 3.0 mass% or more.

On the other hand, in the case where the Cr content is too large, wear resistance is deteriorated due to a decrease in heat resistance. Therefore, the content of Cr in the hard particle powder for sintered body needs to be 40.0 mass% or less. The content of Cr is preferably 30.0 mass% or less.

(6) Mo is more than or equal to 5.0 mass percent and less than or equal to 50.0 mass percent:

mo is a component element added to maintain the hardness of the powder particles. If the Mo content is too small, the wear resistance of the sintered body containing the hard particle powder becomes insufficient. Therefore, the content of Mo in the hard particle powder for a sintered body needs to be 5.0 mass% or more. The content of Mo is preferably 14.0 mass% or more.

On the other hand, in the case where the Mo content is too large, the hardness becomes too high. As a result, the hard particles are broken and fall off from the sintered body containing the hard particle powder, which in turn increases the amount of wear of the sintered body. Therefore, the content of Mo in the hard particle powder for a sintered body needs to be 50.0 mass% or less. The content of Mo is preferably 40.0 mass% or less.

(7)0.1 mass% or more and 30.0 mass% or less of Fe:

fe is an element that functions to increase the diffusivity of the hard particle powder in the iron powder. In the case where the Fe content is too small, the hard particles are broken and fall off from the sintered body containing the hard particle powder due to a decrease in diffusivity in the iron powder. As a result, wear resistance deteriorates. Therefore, the content of Fe in the hard particle powder for the sintered body needs to be 0.1 mass% or more. The content of Fe is preferably 2.0 mass% or more.

On the other hand, if the Fe content is too high, the Co content decreases. Fe is inferior to Co in heat resistance and wear resistance, and therefore, in the case where the Fe content is too large, heat resistance and wear resistance are significantly deteriorated. Therefore, the content of Fe in the hard particle powder for the sintered body needs to be 30.0 mass% or less. The content of Fe is preferably 20.0 mass% or less.

(8) REM is more than or equal to 0.01 mass% and less than or equal to 0.5 mass%:

"REM" is defined as a group of elements consisting of Sc, Y and lanthanides (i.e., La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu). The hard particle powder of the present invention contains at least one lanthanoid element, and the REM is preferably a rare earth metal mixture (mischmetal) such as an alloy or mixture of La, Ce, Nd, Pr, Sm, and Y, from the viewpoint of industrial low cost. REM is a constituent element added for improving the wear resistance of a sintered body containing a hard particle powder without impairing the powder characteristics and sintering characteristics. In the case where the content of REM is too small, REM hardly contributes to improvement of wear resistance of the sintered body. Therefore, the content of REM in the hard particle powder for a sintered body needs to be 0.01 mass% or more. The content of REM is preferably 0.05 mass% or more.

On the other hand, in the case where the content of REM is too large, sintering characteristics are deteriorated due to an increase in the amount of powder oxidation, and furthermore, wear resistance is also reduced. Therefore, the content of REM in the hard particle powder for sintered body needs to be 0.5 mass% or less. The content of REM is preferably 0.3 mass% or less.

2. Method for producing sintered body

A sintered body containing the hard particle powder for sintered body of the present invention can be produced by the following method: (a) mixing the hard particle powder for a sintered body of the present invention, a pure iron powder, and a graphite powder to obtain a mixed powder, (b) press-forming the mixed powder to produce a formed body, and (c) sintering the formed body.

2.1. Mixing step

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 together (mixing step). As the blending amount of each component, it is preferable to select an optimum blending amount according to the purpose. In addition, in order to improve moldability, it is preferable to add a molding lubricant to the raw material.

In the case where the blending 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 in the mixed 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 is too large, the sintering characteristics are degraded. Therefore, the blending amount of the hard particle powder in the mixed powder is preferably 50.0 mass% or less. The blending amount of the hard particle powder is preferably 30.0 mass% or less.

In the case where the blending amount of the graphite powder is too small, the abrasion resistance of the sintered body is lowered. Therefore, the blending amount of the graphite powder in the mixed 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, when the blending amount of the graphite powder is too large, the sintering characteristics are degraded. Therefore, the blending amount of the graphite powder in the mixed powder is preferably 2.0 mass% or less. The blending amount of the graphite powder is preferably 1.5% by mass or less.

2.2. Step of press forming

Subsequently, the mixed powder is press-formed, thereby obtaining a formed body. The press-forming conditions are not particularly limited, and optimum conditions may be selected according to the purpose. Generally, as the forming pressure increases, the press density further increases. After forming, the formed body may be fired in the atmosphere to degrease.

2.3. Sintering step

Subsequently, the formed body is sintered (sintering step).

The sintering conditions are preferably selected to be optimum according to the composition of the compact. Generally, as the sintering temperature increases, a more dense sintered body can be obtained by a shorter time of heat treatment. On the other hand, if the sintering temperature is too high, there is a problem that hard particles excessively diffuse into the iron-based matrix or melt. Although the optimum sintering conditions may vary depending on the composition of the formed body, it is generally preferable to perform sintering at 1,100 ℃ to 1,300 ℃ for 0.5 hours to 3 hours. Further, it is preferable to perform sintering in a reducing atmosphere (for example, in an ammonia decomposition atmosphere).

3. Function of

In the Co-based hard particles containing REM, when the composition is optimized, the wear resistance of the sintered body containing hard particles can be improved without impairing the powder characteristics and sintering characteristics. It is considered that this is because, when an appropriate amount of REM is added to the hard particles, an oxide coating is generated on the surface of the sintered body in a low temperature range of about 600 ℃, and the oxide coating exhibits a lubricating effect.

Examples of the present invention

(examples 1 to 30 and comparative examples 1 to 44)

1. Production of test specimens

1.1 production of hard particle powder

The raw materials were blended to obtain the compositions shown in tables 1 and 2 (unit: mass%). The raw material mixture is melted and a hard particle powder is obtained by an atomization method. REM used in the manufacture is a rare earth metal mixture, which is a mixture of La, Ce, Nd, Pr, Sm and Y. Tables 1 and 2 also show the sintered density of the sintered body containing the hard particle powder and the amount of wear of the sintered body when subjected to the wear resistance test described below.

TABLE 1

TABLE 1 (continuation)

TABLE 2

Table 2 (continuation)

1.2. Production of sintered body

A mixture consisting of 69.2 mass% pure iron powder (ASC100.29), 30 mass% hard particle powder and 0.8 mass% graphite powder (CPB) was prepared. To 100 parts by weight of the mixture, 0.5 part by weight of Zn-St (forming lubricant) was further added, followed by mixing.

Subsequently, the starting material was heated at 8t/cm²Is press-formed under the forming pressure of (1). The shape of the obtained molded article was set to (a) a disk shape having a diameter of 35mm and a thickness of 14mm or (b) a ring shape having an outer diameter of 28mm, an inner diameter of 20mm and a thickness of 4 mm.

Subsequently, the molded body was degreased at 400 ℃ for 1 hour in the atmosphere. And, decomposing the atmosphere at 1,160 ℃ under ammonia (N)₂+3H₂) The degreased body was sintered for 1 hour, thereby obtaining a sintered body.

2. Test method

2.1. Powder characteristics

For the obtained hard particle powder, powder characteristics (particle size distribution, apparent density, flow rate, powder hardness, and oxidation initiation temperature) were investigated. Herein, the particle size distribution was measured (a) according to the Japanese Industrial Standard JIS Z2510-2004, (b) the apparent density was measured according to the Japanese Industrial Standard JIS Z2504-2012, (c) the flow rate was measured according to the Japanese Industrial Standard JIS Z2502-2012, (d) the powder hardness was measured by using a micro hardness measuring instrument, and (e) the oxidation initiation temperature was measured by using a thermobalance, respectively.

2.2. Forming and sintering characteristics

For the produced formed body and sintered body, the forming characteristics and sintering characteristics (forming density, sintering density, chemical composition, sintered body hardness, and radial crushing strength) were investigated.

Herein, the formed density and the sintered density were measured according to Japanese Industrial standards JIS Z2508 and JIS Z2509-2004. The chemical components are obtained by an infrared absorption method. The sintered body Hardness (HRA) was measured by using a rockwell hardness meter. The radial crush strength was measured by using an annular sintered body and an Amsler (Amsler) detector.

2.3. Sintered body wear resistance test

The sintered body was subjected to an abrasion resistance test by using an abrasion tester for a single valve seat (hereinafter also simply referred to as "abrasion tester") as shown in fig. 1. Each of the disk-shaped sintered bodies (diameter: 35mm, and thickness: 14mm) was processed into a valve seat shape and used as a separate wear test specimen. Further, the wear test sample is pressed into the valve seat holder, thereby fixing the wear test sample in the wear tester.

The wear tester was driven under the test conditions shown in table 3. The wear test specimen is worn by hammering by crank drive input while indirectly heating the wear test specimen by heating the valve body with gas flame.

TABLE 3

Time of measurement	10 hours
		Fuel	LPG
Contact rate	3,000 times per minute
		Temperature of sample for wear test	300℃
Driving mode of valve body	Crank shaft
		Rotational speed of valve body	10 times per minute
Valve body surface	Fe-21Cr-9Mn-4Ni-Co alloy welding

Before and after the wear test, the shape of the wear test specimen was measured using a shape measuring instrument. As shown in fig. 2 (an enlarged view of a portion indicated by an arrow a in fig. 1), a difference D in a direction perpendicular to the surface of the wear test specimen was obtained and used as a wear amount of the wear test specimen.

3. Results

3.1. Powder characteristics

Table 4 shows the powder characteristics of the hard particle powders obtained in examples 1 to 3 and comparative examples 9 and 10. Fig. 3 shows the relationship between the temperature and the weight increase of the hard particle powders obtained in example 2 and comparative example 13. From table 4 and fig. 3, the following facts can be found. (1) The particle size distribution and powder characteristics in examples 1 to 3 were almost the same as those in comparative examples 9 and 10. (2) Regarding the particle size distributions in examples 1 to 3 and comparative examples 9 and 10, the difference therebetween was small in both the particle size distribution of-100 to +145 mesh and the particle size distribution of-145 to +200 mesh. Therefore, the particle size distribution is considered to be caused by variations in the powder manufacturing process. (3) The hardness in examples 1 to 3 was almost the same as that in comparative examples 9 and 10. (4) The oxidation initiation temperature in example 2 was lower than that in comparative example 13. This is because the hard particle powder becomes easily oxidized due to the addition of REM.

TABLE 4

3.2. Forming and sintering characteristics

Table 5 shows the characteristics of the formed bodies and sintered bodies obtained in examples 1 to 3 and comparative examples 9 and 10. From table 5, the following facts can be found. (1) In examples 1 to 3 and comparative examples 9 and 10, the compositions were different from each other, but almost the same pressed density, sintered density, and sintered body hardness were obtained. (2) The radial crushing strength in examples 1 to 3 was higher than that in comparative examples 9 and 10. The radial crushing strength is attributed to the sintered body hardness, and therefore, when the sintered body hardness is higher, the radial crushing strength also tends to become higher.

TABLE 5

3.3. Abrasion resistance test

Tables 1 and 2 show the composition of each hard particle powder, the sintered density of the sintered body using the hard particle powder, and the amount of wear of the sintered body in the wear resistance test. From tables 1 and 2, the following facts can be found. (1) In all examples 1 to 30, the abrasion loss was less than 20 μm. On the other hand, in all of comparative examples 1 to 44, the abrasion loss was 20 μm or more. That is, the abrasion amount in examples 1 to 30 was smaller than that in comparative examples 1 to 44.

(2) When examples 1 to 30 and comparative examples 13 to 28 are compared with each other, all of these examples satisfy the preferred component ranges of the present invention except for the presence or absence of REM. Therefore, it was found that in the composition of components according to examples 1 to 30 (except REM), the addition of REM has an effect of improving the wear resistance of the sintered body (valve seat). (3) As shown in comparative examples 29 to 44, it was found that when the content of REM was too large, the effect of improving the wear resistance of the sintered body (valve seat) could not be obtained. From these facts, it can be found that the content of REM is preferably not more than 0.6 mass%. Further, it was found that the content of REM is preferably 0.5 mass% or less, and more preferably 0.25 mass% or less.

(4) In comparative example 1, the abrasion amount was large. It is considered that this is because the C content is too high, and thus the hardness becomes high to break the hard particle powder. (5) In comparative example 2, the abrasion amount was large. It is considered that this is because the Si content is too high, and thus the hardness becomes too high to cause the hard particle powder to fall off. (6) In comparative example 3, the abrasion amount was large. This is considered because the sintered body does not contain Mn and thus no powder oxide film is formed, thereby degrading the lubricating performance. (7) In comparative example 4, the abrasion amount was large. It is considered that this is because the Mn content is high, and therefore the powder oxidation amount increases, thereby deteriorating the sintering characteristics. (8) In comparative example 5, the abrasion amount was large. This is considered because the sintered body does not contain Ni and therefore the heat resistance is lowered. (9) In comparative example 6, the abrasion amount was large. This is considered to be because the Ni content is too high, and therefore the amount of Co as a balance element is reduced in turn, thereby lowering the heat resistance and wear resistance.

(10) In comparative example 7, the abrasion amount was large. This is considered because the sintered body does not contain Cr, and therefore the heat resistance is lowered. (11) In comparative example 8, the abrasion amount was large. This is considered to be because the Cr content is too high, and therefore the amount of Co as a balance element is conversely reduced, thereby lowering the heat resistance and wear resistance. (12) In comparative example 9, the abrasion amount was large. This is considered to be because the Mo content is too small, and therefore the hardness is lowered, thereby lowering the wear resistance. (13) In comparative example 10, the abrasion amount was large. It is considered that this is because the Mo content is too high, and therefore the hardness becomes too high, thereby causing the hard particle powder to fall off. (14) In comparative example 11, the abrasion amount was large. This is considered to be because the sintered body does not contain Fe, and therefore the diffusivity in the iron powder is reduced, so that the hard particle powder is easily dropped. (15) In comparative example 12, the abrasion amount was large. This is considered to be because the Fe content is too high and thus the heat resistance is lowered.

(16) In comparative examples 13 to 28, the abrasion amount was large. This is considered because the sintered body does not contain REM and therefore oxidation does not occur at low temperature, thereby degrading the lubricating performance on the valve body surface. (17) In comparative examples 29 to 44, the abrasion amount was large. It is considered that this is because the content of REM is too high, and thus the amount of powder oxidation increases to degrade the sintering characteristics.

Based on the above, it was found that in the case where REM is added to a hard particle powder made of a predetermined composition system, the wear resistance of a sintered body (valve seat) can be improved while substantially not impairing the powder characteristics and sintering characteristics, thereby enabling to obtain a sintered body excellent in wear resistance.

The embodiments of the present invention have been described in detail so far, but the present invention is not limited to the above-described embodiments, and various modifications or changes can be made within the scope of the gist of the present invention.

The present application is based on japanese patent application No.2018-026177 filed on 16.2.2018, the entire contents of which are incorporated herein by reference.

Industrial applicability

In order to improve wear resistance, the hard particle powder for sintered bodies according to the present invention may be used as a hard particle powder contained in various sintered bodies that can be used as valve seats, valve guides (valve guides), or other mechanical structure parts.

Claims

1. A hard particle powder for a sintered body, which is composed of:

mn is more than or equal to 4.0 percent and less than or equal to 7.0 percent by mass,

ni is more than or equal to 27 percent and less than or equal to 35.0 percent by mass,

0.1 to 10 mass percent of Cr,

mo is more than or equal to 35 percent and less than or equal to 50.0 percent by mass,

0.1 to 7 mass% of Fe, and

REM comprises at least one element of the lanthanide series,

the balance being Co and unavoidable impurities.

2. The hard particle powder for a sintered body according to claim 1, wherein the content of Mn is:

mn is not less than 5 mass% and not more than 7.0 mass%.

3. The hard particle powder for a sintered body according to claim 1, wherein the content of Ni is:

ni is more than or equal to 27 mass percent and less than or equal to 30 mass percent.

4. The hard particle powder for a sintered body according to claim 2, wherein the content of Ni is:

5. The hard particle powder for a sintered body according to any one of claims 1 to 4, wherein the content of Fe is:

fe is between 2.0 and 7 percent by mass.

6. A sintered body comprising:

hard particle powder,

Pure iron powder, and

the graphite powder is mixed with the graphite powder,

wherein the hard particle powder is composed of:

0.1 to 10 mass percent of Cr,

0.1 to 7 mass% of Fe, and

REM comprises at least one element of the lanthanide series,

the balance being Co and unavoidable impurities.

7. The sintered body as claimed in claim 6, wherein the content of Mn is:

mn is not less than 5 mass% and not more than 7.0 mass%.

8. The sintered body according to claim 6, wherein the content of Ni is:

9. The sintered body according to claim 7, wherein the content of Ni is:

10. The sintered body according to any one of claims 6 to 9, wherein the content of Fe is:

fe is between 2.0 and 7 percent by mass.