JP2002356704A - Alloy powder for forming wear-resistant hard phase and method for producing wear-resistant sintered alloy using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide powder which is excellent in forming a hard phase dispersed in a sintered alloy for a wear-resistant member, and a production method for a sintered alloy in which the hard phase formed by the powder is dispersed. SOLUTION: The alloy powder for forming a wear-resistant hard phase has a composition containing, by mass, 1.0 to 12% Si, 20 to 50% Mo and 0.5 to 5.0% Mn, and the balance at least one or more kinds selected from Fe, Ni and Co with inevitable impurities. This alloy is added to master alloy powder using iron powder or low alloy steel powder, and they are mixed. This powdery mixture is compacted, and is thereafter sintered in the temperature range of 1,000 to 1,250 deg.C to obtain the wear-resistant sintered alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder for forming a hard phase dispersed in a metal structure of a sintered alloy for a wear-resistant member, and a method for producing a wear-resistant sintered alloy using the same. About.

[0002]

2. Description of the Related Art Sintered alloys used for wear-resistant members include:
A method of dispersing a phase whose hardness is increased by an intermetallic compound or carbide, that is, a so-called hard phase, is often used, and is considered to be particularly effective for a member used at a high temperature. Conventionally, to form such a hard phase, FeM
o, a ferroalloy ground powder such as FeCr or a ceramic powder was added, but there were problems with the compressibility of the mixed powder, mold wear, and wettability with the matrix. In addition, Co group or F
It is also common to apply e-based thermal spraying powders as hard phase forming powders, but rarely one whose components are optimized for powder metallurgy. Accordingly, the applicant of the present application has disclosed Japanese Patent Publication No. 61-814.
As shown in No. 2, there has been proposed a mixture of a base powder such as a low alloy steel or a stainless steel and a Mo-containing hard phase forming powder containing iron having good wettability after sintering.

[0003]

However, the powders described in the above-mentioned publications have a case where they exhibit very excellent abrasion resistance and a case where they are greatly worn, and have a problem in stability of performance. It has been found that the causes are insufficient reinforcement of the matrix supporting the precipitates and the adhesion between the hard phase and the matrix.

[0004] The present invention has been made in view of such a situation, and a powder optimal for forming a hard phase dispersed in a sintered alloy for a wear-resistant member, and a powder formed by such a powder. It is an object of the present invention to provide a method for producing a sintered alloy in which a hard phase is dispersed.

[0005]

Means for Solving the Problems The present inventor carried out various improvement studies on the components of the hard phase dispersed in the sintered alloy. It was completed. More specifically, the effect of strengthening the matrix of Mn and improving the adhesion, and the effect of strengthening the matrix with Cr, W, V, and Nb were obtained, so that the wear resistance was higher than that of the conventional product. Furthermore, they have found that by replacing the base material of the hard phase forming powder with Co or Ni, these diffuse into the mother alloy steel and change the properties of the sintered alloy. The present invention has been made based on such knowledge, and has the following features.

First, the wear-resistant hard phase forming alloy powder of the present invention will be described. The first powder of the present invention has a mass ratio of S
i: 1.0 to 12%, Mo: 20 to 50%, Mn: 0.
5 to 5.0%, with the balance being at least one of Fe, Ni, and Co and unavoidable impurities. Further, the second powder of the present invention has a mass ratio of S
i: 1.0 to 12%, Mo: 20 to 50%, Mn: 0.
5 to 5.0%, Cr: 15% or less, and the balance Fe,
It is characterized by comprising at least one or more of Ni and Co and unavoidable impurities. Each of the powders of the present invention may further contain at least one of W, V, and Nb in a mass ratio of 5% or less.

Next, a method for producing a wear-resistant sintered alloy according to the present invention is characterized in that the powder of the present invention: 5 to 50% by mass is added to a base alloy powder based on iron powder or low alloy steel powder. After compression molding of the mixed powder thus mixed, 1000 to 12
It is characterized in that it is sintered in a temperature range of 50 ° C. In this method, the metal sulfide powder may be contained in the mother alloy powder.

Hereinafter, the function of the present invention and the reasons for limiting the content of the components will be described. Si: Si mainly reacts with Mo to form Mo silicide having excellent wear resistance and lubricity, and contributes to improvement of the wear resistance of the sintered alloy. If the content of Si is less than 1% by mass, a sufficient Mo silicide cannot be obtained, and a sufficient effect of improving wear resistance cannot be obtained. Conversely, Si is 12% by mass.
If it exceeds, not only the hardness of the powder becomes high and the compressibility at the time of molding is impaired, but also a Si oxide film is formed on the surface of the powder to inhibit diffusion with the mother alloy steel powder, and the adhesion of the hard phase is reduced. descend. If the sticking property is low, the impact during use causes the hard phase to fall off, which acts on the abrasive powder and conversely reduces the wear resistance. Therefore, the Si content is set to 1 to 12% by mass.

Mo: Mo mainly reacts with Si to form Mo silicide having excellent wear resistance and lubricity, and contributes to improvement of the wear resistance of the sintered alloy. If Mo is less than 20% by mass, sufficient Mo silicide cannot be obtained, and a sufficient effect of improving wear resistance cannot be obtained. On the other hand, if Mo exceeds 50% by mass, not only the hardness of the powder becomes high and the compressibility at the time of molding is impaired, but also the hard phase formed becomes brittle, so that a part thereof is chipped by impact and the abrasive powder Conversely, the wear resistance is reduced by the action. Therefore, the Mo content is 20 to 50.
% By mass.

Mn: Mn contributes to strengthening of the base portion other than Mo silicide of the hard phase. By strengthening the base,
Since Mo silicide can be prevented from flowing and falling, excellent abrasion resistance can be exhibited even under severe conditions. Also, Mn
Has an effect of improving the fixability of the hard phase to the mother alloy steel, so that the hard phase itself can be prevented from falling off and the wear resistance can be improved. These effects are insufficient when Mn is less than 0.5% by mass. Conversely, when Mn is more than 5% by mass, a Mn oxide film is formed on the surface of the powder to inhibit diffusion with the mother alloy steel powder. And the fixation of the hard phase is reduced. If the adhesion is low, the impact during use causes the hard phase to fall off, which acts on the abrasive powder and conversely reduces the wear resistance. Therefore, the Mn content is set to 0.5 to 5% by mass.

Fe, Ni, Co: These elements serving as the base material of the hard particle powder mainly diffuse into the mother alloy steel during sintering,
It contributes to strengthening of the base alloy steel base and improvement of the adhesion. Also,
Reinforcement of the base part other than Mo silicide in the hard phase,
Form a compound with (Si) to increase wear resistance. Fe
In the case of (1), the diffusibility into the master alloy steel is good, so that the hard phase has good fixation. In addition, the cost can be reduced, so that it is suitable for use as a general-purpose member. Ni
In case (1), since the austenite structure having excellent corrosion resistance is exhibited in and around the hard phase, the corrosion resistance of the sintered alloy can be improved, which is suitable for use in members requiring corrosion resistance. Co can improve the heat resistance of the hard phase and its surroundings, and is therefore suitable for use in members requiring heat resistance. Also, by combining two or more of these elements, an alloy having each characteristic can be obtained, and therefore, the component ratio can be adjusted to the environment in which the member is used.

Cr: Like Cr, Cr also contributes to strengthening of the base portion other than Mo silicide in the hard phase. Further, it diffuses into the mother alloy steel and contributes to the improvement of the wear resistance of the mother alloy steel. If the content of Cr exceeds 15% by mass, the amount of oxygen in the powder increases and an oxide film is formed on the powder surface to inhibit the progress of sintering, and the oxide film hardens the powder, resulting in a decrease in compressibility. Therefore, the Cr content is set to 15% by mass or less because the strength of the sintered alloy is reduced and the wear resistance is reduced.

W, V, Nb: These elements form carbides in and around the hard phase and contribute to the improvement of wear resistance. Cr
It is preferable to disperse the base stations strengthened by the above because a great effect can be obtained. In addition, these elements are M
oSince there is also an effect of making the silicide fine, the hard phase is less likely to become brittle. The same effect can be obtained by using these elements alone or in combination of two or more.

Addition amount of hard phase-forming powder: The larger the addition amount of hard phase-forming powder, the better the abrasion resistance, but 5% by mass.
If the amount is less than 50% by mass, the effect is poor. If the amount exceeds 50% by mass, the compressibility of the mixed powder is reduced, the density and strength after sintering are reduced, and the wear resistance is reduced. did.

Sintering temperature: The structure of the mother alloy steel of the alloy of the present invention is preferably pearlite or sorbite, more preferably bainite or martensite. Therefore, it is desirable to mix graphite powder with the mixed powder of the method of the present invention.
In the method of the present invention, the sintering temperature affects the diffusion of graphite and the progress of sintering. However, if the temperature is less than 1000 ° C., sintering becomes insufficient and satisfactory wear resistance cannot be obtained. Conversely 1
If the temperature exceeds 250 ° C., the hard phase melts and disappears. Therefore, the sintering temperature was limited to 1000 to 1250 ° C.

[0016]

Embodiments of the present invention will be described below. First, a master alloy steel powder (base powder) B1 composed of the components shown in Table 1
~ B5 were prepared. On the other hand, Fe powder, Cu powder, Fe-3C
r-0.3V-0.3Mo perfect alloy powder, Fe-6.5C
o-1.5Ni-1.5Mo perfect alloy powder (all numerical values are mass%), graphite powder, molding lubricant, and hard phase forming powder P inside and outside the claims of the present invention comprising the components shown in Table 2.
01 to P29 were prepared. Next, these powders and forming lubricants were added in predetermined amounts to the mother alloy steel powders B1 to B5, and mixed powders of Sample Nos. 01 to 50 composed of the components shown in Table 3 were prepared. Next, these mixed powders were molded into a predetermined shape at a molding pressure of 650 MPa, and these molded bodies were sintered in an ammonia decomposition gas for 60 minutes to obtain sintered bodies.
The sintering temperature was basically 1150 ° C., but as shown in Table 3, sintering was performed at other temperatures.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

Next, the sintered alloys of Sample Nos. 01 to 50 were subjected to measurement of radial crushing strength and a simple wear test. Table 4 shows the results. The simple abrasion test was performed in a state where hitting and sliding input were applied at a high temperature. In particular,
A sintered alloy processed into a ring shape having a 45 ° tapered surface on the inner diameter surface is press-fitted into an aluminum alloy housing,
A disk-shaped mating member having a 45 ° taper surface on the outer diameter surface made of SUH-36 material is moved up and down by a motor-driven eccentric cam to move the piston upward and downward, so that the taper between the sintered alloy and mating member is obtained. The faces collided repeatedly. In this test, the temperature of the sintered alloy was set to 250 ° C. while the mating material was heated by a burner, the number of taps in the simple wear test was 2800 times / minute, and the repetition time was 15 hours. The wear amount VS in Table 4 is the wear amount of the example subjected to the test, and the wear amount V is the wear amount of the mating material.

[0021]

[Table 4]

Next, the present embodiment will be considered with reference to FIGS. 1 to 9 to clarify the effects of the present invention. The numbers shown in these figures are sample numbers.

FIG. 1 shows the changes in the wear amount and radial crushing strength of Sample Nos. 01 to 05 in which the amount of Mo in the hard phase forming powder was changed. According to this, the amount of Mo is 20 to 50% by mass.
The wear amount is low and stable in the range of
It can be said that Mo silicide formed by reacting with a suitable amount is formed and exhibits good wear resistance. On the other hand, when the amount of Mo is less than 20% by mass or more than 50% by mass, the amount of abrasion tends to increase. It is assumed that the material becomes brittle and cracks occur, and the wear resistance is reduced. With respect to the strength based on the radial crushing strength, a slight decrease is observed with an increase in the Mo content, but within this range, there is no practical problem.

FIG. 2 shows the changes in the wear amount and radial crushing strength of Sample Nos. 06 to 11 in which the amount of Si in the hard phase forming powder was changed. According to this, when the Si content is in the range of 1 to 12% by mass, the wear amount is low, and in this range, an appropriate amount of Mo silicide formed by reacting with Mo is formed, indicating good wear resistance. On the other hand, when the amount of Si is less than 1% by mass, the amount of wear increases sharply, and when the amount of Si exceeds 12% by mass, the amount of wear tends to increase. It is presumed that when the content is less than 1% by mass, Mo silicide is insufficient, and when the content is more than 12% by mass, the fixation of the hard phase is deteriorated, so that the wear resistance is reduced. Further, it is recognized that the strength decreases with an increase in the amount of Si.

FIG. 3 shows the changes in the wear amount and radial crushing strength of Sample Nos. 12 to 15 in which the amount of Mn in the hard phase forming powder was changed. According to this, the Mn content is 0.5 to 5% by mass.
In this range, the amount of wear is low, and in this range, it is possible to prevent the Mo silicide from dropping off due to the strengthening of the matrix and the improvement in the fixation of the hard phase, and it is possible to exhibit good wear resistance. On the other hand, when the amount of Mn is less than 0.5% by mass or more than 5% by mass, the amount of abrasion tends to increase rapidly, and it can be seen that the effect of abrasion resistance cannot be obtained. Further, it is recognized that the strength decreases with an increase in the amount of Mn.

FIG. 4 shows that the base alloy of the hard phase forming powder is F
e shows the wear amount and radial crushing strength of sample No. 03, Ni: sample No. 16, Co: sample No. 17, and alloy without addition of the hard phase forming powder: sample No. 18. According to this, the alloys to which the hard phase-forming powder was added all had significantly reduced abrasion amounts and exhibited good wear resistance as compared with the alloys to which no hard phase forming powder was added, and the effect is clear.

FIG. 5 shows the changes in the wear amount and radial crushing strength of Sample Nos. 03 and 19 to 21 in which the amount of Cr in the hard phase forming powder was changed. According to this, the amount of Cr was 15% by mass.
It can be seen that the wear amount is low in the following range, and that when the amount exceeds 15% by mass, the strength decreases and the wear amount increases. When the amount of Cr exceeds 15% by mass, the progress of sintering is hindered, the strength is reduced, and the wear resistance is reduced.

FIG. 6 shows alloys containing at least one of W, V, and Nb as additional elements: Sample Nos. 22 to
30 shows the wear amount. According to this, it can be understood that the wear amount of each alloy is suppressed to 100 μm or less, and that the added element greatly contributes to the improvement of the wear resistance.

FIG. 7 shows the changes in the wear amount and radial crushing strength of Sample Nos. 18, 31 to 37 in which the addition amount of the hard phase forming powder was changed. According to this, when the addition amount of the hard phase forming powder is less than 5% by mass, the amount of wear tends to increase, while when it exceeds 50% by mass, the amount of wear tends to increase. In the range of 5 to 50% by mass, the amount of abrasion is suppressed low, and it is understood that the effect of improving the abrasion resistance by the hard phase forming powder of the present invention is exhibited in this range. Further, regarding the strength, it is recognized that the strength is reduced by increasing the hard phase forming powder, and the strength is insufficient when the content exceeds 50% by mass.

FIG. 8 shows sample No. 03 with different sintering temperatures.
38 shows changes in wear amount and radial crushing strength of Nos. 38 to 42. According to this, when the sintering temperature is in the range of 1000 to 1250 ° C., the amount of wear is kept low and high strength is maintained. If the temperature is less than 1000 ° C. and exceeds 1250 ° C., the amount of wear increases and the strength tends to decrease. 1000 ° C
If it is less than 1, the sintering is insufficient, and if it exceeds 1250 ° C., the hard phase melts and disappears, which indicates that such a tendency occurs.

FIG. 9 shows Fe—C based alloys in which the amount of C added to the base powders B1 and B2 was changed: Sample Nos. 47 and 48
And Fe-C obtained by adding C and Cu to the base powder B3
uC-based alloy: Sample No. 49 and Fe-Cr-C-based alloy obtained by adding C and Cr to base powder B4: Sample No. 5
0 and Fe- in which C and Co are added to the base powder B5.
Co-C alloy: Sample No. 18 and sample Nos. 43 to 46 and 03 obtained by adding a hard phase forming powder thereto show the wear amount. According to this, the wear of both alloys was significantly reduced by the addition of the hard phase forming powder,
It is understood that the addition of the hard phase forming powder greatly contributes to the improvement of the wear resistance.

[0032]

As described above, according to the alloy powder for forming a wear-resistant hard phase of the present invention, the most suitable powder for forming a hard phase dispersed in a sintered alloy for a wear-resistant member. In addition, according to the method for producing a wear-resistant sintered alloy of the present invention, there is an effect that a sintered alloy in which the hard phase formed by the powder of the present invention is dispersed can be suitably and efficiently produced.

[Brief description of the drawings]

FIG. 1 is a diagram showing the effect of the amount of Mo in a hard phase forming powder on the amount of wear and radial crushing strength in Examples of the present invention.

FIG. 2 is a graph showing the effect of the amount of Si in a hard phase forming powder on the amount of wear and radial crushing strength in Examples of the present invention.

FIG. 3 is a graph showing the effect of the amount of Mn in a hard phase forming powder on the amount of wear and radial crushing strength in Examples of the present invention.

FIG. 4 is a graph showing the wear amount of an alloy in which the type of the base alloy of the hard phase forming powder is changed and an alloy to which the hard phase forming powder is not added in the example of the present invention.

FIG. 5 is a graph showing the effect of the amount of Cr in a hard phase forming powder on the amount of wear and radial crushing strength in Examples of the present invention.

FIG. 6 is a diagram showing a wear amount of a sintered alloy in which an element for improving wear resistance is added to a hard phase forming powder in an example of the present invention.

FIG. 7 is a graph showing the effect of the amount of the hard phase forming powder added on the wear amount and the radial crushing strength in the examples of the present invention.

FIG. 8 is a diagram showing the effect of the sintering temperature on the amount of wear and radial crushing strength in the example of the present invention.

FIG. 9 is a graph showing the effect of the presence or absence of a hard phase forming powder on the amount of wear in various Fe—C alloys in Examples of the present invention.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22C 19/07 C22C 19/07 J 27/04 102 27/04 102 38/00 302 38/00 302Z 38 / 12 38/12 (72) Inventor Koichiro Hayashi 7-10-25-206 Minamimasu, Kashiwa-shi, Chiba F-term (reference) 4K018 AA07 AA10 AA21 AA25 CA01 DA21 KA14 KA18

Claims (5)

[Claims] 1. A mass ratio of Si: 1.0 to 12%, M
o: 20 to 50%, Mn: 0.5 to 5.0%, and the balance is at least one or more of Fe, Ni, and Co and an unavoidable impurity, and is an alloy for forming a wear-resistant hard phase. Powder. 2. A mass ratio of Si: 1.0 to 12%, M
o: 20 to 50%, Mn: 0.5 to 5.0%, Cr: 1
An alloy powder for forming a wear-resistant hard phase, wherein the alloy powder comprises 5% or less, and the balance is at least one of Fe, Ni, and Co and inevitable impurities. 3. The alloy powder for forming a wear-resistant hard phase,
3. The composition according to claim 1, further comprising at least one of W, V, and Nb in a mass ratio of 5% or less.
2. The alloy powder for forming a wear-resistant hard phase according to item 1. 4. An alloy powder for forming a wear-resistant hard phase according to claim 1, wherein 5 to 50% by mass is added to a base alloy powder based on iron powder or low alloy steel powder. After compression molding of the mixed powder thus mixed, 1000 to 12
A method for producing a wear-resistant sintered alloy, comprising sintering in a temperature range of 50 ° C. 5. The method for producing a wear-resistant sintered alloy according to claim 4, wherein the mother alloy powder contains a metal sulfide powder.