JP2010144237A - Wear-resistant sintered alloy and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive wear-resistant sintered alloy which has such high corrosion resistance as to be used in an internal combustion engine using an alcohol fuel, and to provide a method for producing the same. <P>SOLUTION: The wear-resistant sintered alloy has a total composition comprising, by mass ratio, 1.58-18.55 mass% Cr, 0.54-2.54 mass% Ni, 2.67-16.84 mass% Mo, 0.15-4.5 mass% Si, 2.25-33.30 mass% Co, 0.05-0.42 mass% Mn, 0.5-1.5 mass% C and the balance Fe with unavoidable impurities; and has a metallurgical structure in which a hard phase having a composition comprising 15-35% Mo, 1-10% Si, 10-40% Cr and the balance Co with unavoidable impurities is dispersed in an Fe-Ni-Mo-C based alloy matrix by 15-45%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wear-resistant sintered alloy having excellent wear resistance at high temperatures and a manufacturing method, and more particularly to a technique suitably used for a valve seat of an internal combustion engine.

  Sintered alloys are applied to valve seats of internal combustion engines because they have a high degree of freedom in alloy design and are easy to add various characteristics such as heat resistance and wear resistance as compared with melted materials. Many of such wear-resistant sintered alloys for valve seats are obtained by dispersing hard particles of high hardness on an iron-based alloy base mainly for the purpose of improving wear resistance. For example, ferroalloy particles such as ferromolybdenum and ferrotungsten are added to the raw material powder and sintered to disperse the ferroalloy particles in the iron-base alloy matrix (Patent Document 1, etc.), high-speed tool steel powder or dies. Known are steel powders in which a hard phase in which metal carbide is precipitated and dispersed is dispersed in an iron-base alloy matrix (Patent Document 2 and the like). In particular, when high wear resistance is required, a Co-based alloy powder such as a Co—Cr—W alloy (Patent Document 1) or a Co—Mo—Si alloy (Patent Document 3 or the like), Ni It is known that it is preferable to add a base alloy powder (eg, Patent Document 4) to the raw material powder and disperse it as a hard phase.

JP-A 64-015349 Japanese Patent Laid-Open No. 09-195012 JP 56-152947 A Japanese Patent Laid-Open No. 10-046298

  In recent years, wear-resistant sintered alloys in which a hard phase of a Co—Mo—Si based alloy is dispersed have become costly due to rising prices of Co and Mo. In addition, due to recent environmental problems and crude oil depletion problems, the use of biological alcohol fuel as fuel for internal combustion engines is increasing. However, since alcohol fuel generates an acidic substance during combustion, higher corrosion resistance is required for wear-resistant sintered alloys used for valve seats. Accordingly, an object of the present invention is to provide a wear-resistant sintered alloy that is inexpensive and has higher corrosion resistance than before, and a method for producing the same. In the following description, “%” represents all percentages in mass ratio, that is, “mass%”.

  The wear-resistant sintered alloy of the present invention has a mass ratio of Cr: 1.58 to 18.55% by mass, Ni: 0.54 to 2.54% by mass, Mo: 2.67 to 16 .84% by mass, Si: 0.15 to 4.5% by mass, Co: 2.25 to 33.30% by mass, Mn: 0.05 to 0.42% by mass, C: 0.5 to 1.5 In the Fe-Co-C alloy base, the composition is Mo: 15 to 35%, Si: 1 to 10%, Cr: 10 to 40%, and the balance. Exhibits a metal structure in which a hard phase composed of Co and inevitable impurities is dispersed by 15 to 45%.

  In this case, Mn: 5 mass% or less is included in the composition of the hard phase so that a part of Co in the hard phase is replaced with Fe, or in the overall composition, Mn: 2.25 mass% or less. It is preferable to add. Moreover, it is preferable to add Ni so that it may become 5.0 mass% or less with respect to the whole composition, or to add Cu so that it may become 5.0 mass% or less with respect to the whole composition. Further, at least one machinability improving substance powder selected from the group consisting of lead, molybdenum disulfide, manganese sulfide, boron nitride, calcium metasilicate mineral, calcium fluoride is added to the pores and grain boundaries of the sintered alloy. It is preferable to further disperse 3 to 2% by mass, or to fill at least one of lead, lead alloy, copper, copper alloy, and acrylic resin in the pores of the sintered alloy.

  Moreover, the manufacturing method of the wear-resistant sintered alloy of the present invention is such that the composition is in mass ratio, Ni: 1 to 3% by mass, Mo: 0.5 to 2% by mass, Cr: 0.1 to 1% by mass. , Mn: 0.1 to 0.5% by mass, the balance of the iron alloy powder consisting of Fe and inevitable impurities, the composition is Mo: 15 to 35%, Si: 1 to 10%, Cr: 10 Hard phase forming powder consisting of ˜40% and the balance consisting of Co and inevitable impurities: 15 to 45% and graphite powder: 0.5 to 1.5%, and the mixed raw material powder is pressed into a desired shape Powder molding is performed, and the obtained molded body is sintered.

  In this case, it is preferable that a part of Co in the hard phase forming powder is replaced with Fe, or that the hard phase forming powder further includes Mn: 5% by mass or less. Moreover, it is possible to add nickel powder to the raw material powder so as to be 5.0% by mass or less with respect to the whole composition, or add copper powder to the raw material powder so that it becomes 5.0% by mass or less with respect to the whole composition. preferable. Further, at least one machinability improving substance powder selected from the group consisting of lead powder, molybdenum disulfide powder, manganese sulfide powder, boron nitride powder, calcium metasilicate mineral powder and calcium fluoride powder is used as the raw material powder. Further, 3 to 2% by mass or infiltration of one of lead, lead alloy, copper, copper alloy and acrylic resin in the pores of the wear-resistant sintered alloy obtained by sintering or It is preferable to impregnate.

  The wear-resistant sintered alloy of the present invention reinforces the iron base alloy base and the hard phase alloy base using relatively inexpensive Cr, and a passive oxide film is formed by Cr, so even in a corrosive environment. Excellent corrosion resistance and wear resistance. Therefore, the present invention is suitable for a valve seat of an internal combustion engine that uses alcohol fuel as fuel.

[Hard phase]
As in the prior art, the hard phase of the present invention is dispersed in the matrix by adding the hard phase forming powder to the raw material powder and sintering it. And in the hard phase of this invention, in improving Co-Mo-Si type | system | group hard phase, it is essential that the content of Cr was increased significantly. Therefore, the action of Co, Mo and Si is almost the same as in the case of the prior art.

Co:
Co that forms the alloy base of the hard phase improves the heat resistance of the base by dissolving in the base and improves the high temperature strength and the high temperature wear resistance. Further, Co in the hard phase diffuses into the base and strengthens the base in solid solution, and firmly bonds the hard phase to the base. In addition, a part of Co forms molybdenum silicide, chromium silicide and their composite silicide together with Mo, Cr and Si, and serves as the core of the hard phase to prevent plastic flow and adhesion of the base, Contributes to improved wear resistance.

Mo:
Mo dissolves in the base to strengthen the base and has the effect of improving the hardenability of the base structure, contributing to the improvement of the strength and wear resistance of the base. Mo forms a hard molybdenum silicide mainly with Si, and a part reacts with Cr and Co to form a composite silicide to form a hard phase nucleus. For this reason, plastic flow and adhesion of the base can be prevented, and wear resistance can be improved. Here, if the Mo content in the hard phase forming powder is less than 15%, the base strengthening becomes insufficient, and a sufficient amount of silicide does not precipitate, resulting in poor pinning effect and wear resistance. Sex is reduced. On the other hand, if the content exceeds 35%, the hard phase forming powder becomes hard and compressibility is impaired, and the amount of silicide increases, so that the wear of the counterpart part is promoted. For this reason, the amount of Mo in the hard phase forming powder is set to 15 to 35%.

Si:
Si combines with Mo, Co, and Cr to form hard molybdenum silicide, chromium silicide, and composite silicide thereof to improve wear resistance. If the amount of Si in the hard phase forming powder is less than 1%, a sufficient amount of silicide does not precipitate, and if it exceeds 10%, the hard phase forming powder becomes hard and compressibility is impaired. Worsen. For this reason, the amount of Si in hard phase formation powder shall be 1-10%.

Cr:
Cr dissolves in the hard phase alloy base to strengthen the hard phase alloy base, and at the time of sintering, diffuses into the base of the sintered alloy mainly composed of Fe and contributes to strengthening of the base. Further, Cr diffused in the Fe base of the sintered alloy forms a passive oxide film on the surface of the wear-resistant component, and contributes to improvement of corrosion resistance in a corrosive environment. Furthermore, a part of Cr forms a hard chromium silicide or composite silicide together with Si. Such Cr is relatively cheaper than Co and Mo, and the amount of Co is decreased by increasing the Cr content, so that the hard phase forming alloy powder becomes cheaper and the wear-resistant sintered alloy is less expensive. Can be manufactured. When Cr having the above action is less than 10% in the composition of the hard phase forming alloy powder, the above-mentioned effects of strengthening the base and improving the corrosion resistance are poor. On the other hand, if the Cr content in the hard phase forming alloy powder exceeds 40%, the oxide film formed on the surface of the powder becomes strong, so that the progress of sintering is inhibited and the oxide film hardens the powder and is compressed. Sex is reduced. Therefore, the strength of the sintered alloy is reduced, and the wear resistance is reduced. For this reason, the Cr amount in the hard phase forming powder is set to 10 to 40%.

  In the present invention, by setting the Cr content of the hard phase forming powder forming the hard phase as described above, it becomes possible to replace a part of Co forming the hard phase alloy base with Fe. That is, since Cr dissolved in Fe forms a passive oxide film and improves the corrosion resistance in a corrosive environment, it is possible to apply inexpensive Fe to a part of expensive Co in the hard phase. Here, up to 80% of the amount of Co in the alloy base of the hard phase can be replaced with Fe.

Mn:
Further, in the present invention, Mn can be contained in the hard phase forming powder, and Mn can be dissolved in the hard phase alloy base formed after sintering, thereby strengthening the hard phase alloy base. Strengthening the hard-phase alloy base in this way prevents the flow and detachment of silicides (molybdenum silicides, chromium silicides and their composite silicides) that precipitate in the hard phase, so that they have excellent resistance to severe conditions. Abrasion can be demonstrated. Further, Mn diffuses into the Fe base of the sintered alloy to improve the adhesion of the hard phase, and prevents the hard phase from falling off and improves the wear resistance. When Mn exceeds 5% in the composition of the hard phase forming powder, a Mn oxide film is formed on the powder surface layer to inhibit diffusion during sintering, and the sticking property of the hard phase is lowered. For this reason, the upper limit of the amount of Mn in the hard phase forming powder is 5%.

  If the amount of such hard phase forming powder added to the raw material powder is less than 15%, sufficient wear resistance cannot be obtained. On the other hand, the hard phase forming powder of the present invention is obtained by increasing the amount of Cr in the conventional Co—Mo—Si based hard phase forming powder. Increases the compressibility. However, since soft iron powder is used as the main raw material of the raw material powder, it is possible to add a hard phase forming powder equal to or higher than that using the Fe alloy powder as the main raw material as in the past. . Here, when the addition amount of the hard phase forming powder to the raw material powder exceeds 45%, the compressibility of the raw material powder is significantly lowered. For this reason, the addition amount of the hard phase forming powder to the raw material powder is 15 to 45%.

  The hard phase dispersed in the matrix of the wear resistant sintered alloy is formed by adding the hard phase forming powder to the raw material powder and sintering. As described above, when the amount of the hard phase forming powder added to the raw material powder is 15 to 45%, the hard phase dispersed in the matrix of the wear-resistant sintered alloy is 15 to 45%. In addition, since the composition of the hard phase forming powder is Mo: 15 to 35%, Si: 1 to 10%, Cr: 10 to 40%, and the balance is Co and inevitable impurities as described above. The Co content is 2.25 to 33.3%, the Cr content is 1.5 to 18%, the Mo content is 2.25 to 15.75%, and the Si content is 0.15 to 4.5%. Further, when Mn is contained in the hard phase forming powder, the amount of Mn in the entire composition is 2.25% or less.

[base]
In the present invention, by using the above hard phase, Cr is diffused in the matrix to form a passive oxide film, thereby improving the corrosion resistance of the matrix. Therefore, it is possible to configure the base with an inexpensive Fe alloy without using expensive Co for the base.

Ni, Mo, Cr, Mn:
The base uses bainite as the metal structure of the base from the viewpoint of self wear resistance and opponent attack of the wear resistant sintered alloy and from the viewpoint of self strength. Addition of alloy elements such as Mo, Ni, Cr, etc. is effective for the bainite formation of such a base structure, and in order to exert this effect uniformly on the entire surface of the base structure, iron obtained by alloying these alloy components with Fe It is applied in the form of alloy powder. Specifically, the composition of the iron alloy powder is, by mass ratio, Ni: 1-3%, Mo: 0.5-2%, Cr: 0.1-1%, Mn: 0.1-0.5 %, And the balance consists of Fe and inevitable impurities. That is, when Ni is less than 1%, Mo is less than 0.5%, Cr is less than 0.1%, and Mn is less than 0.1%, the bainite of the base becomes insufficient. On the other hand, if Ni is more than 3%, Mo is more than 2%, Cr is more than 1%, and Mn is more than 0.5%, the hardness of the alloy powder is increased and the compressibility is lowered. This will cause a decrease in performance.

Additional Ni, Cu:
When further improvement of wear resistance is desired, nickel powder or copper powder should be added to the raw material powder to make a part of the base structure high-strength martensite and a mixed structure of bainite and martensite. Can do. That is, Ni and Cu have a large effect of improving the hardenability of the base, and nickel powder and copper powder have low hardness. Therefore, it is easy to add nickel powder and copper powder to the above iron alloy powder. Furthermore, it can be a mixed structure of bainite and martensite. However, if the addition amount of nickel powder exceeds 5%, a large amount of Ni-rich austenite with low wear resistance will remain in the base, and if the addition amount of copper powder exceeds 5%, a soft copper phase will remain. Will precipitate in the base and reduce the strength of the base. For this reason, the upper limit of the addition amount of nickel powder is 5%, and the upper limit of the addition amount of copper powder is 5%.

C:
C is added to solidify the Fe base to strengthen the Fe base and to make the base structure have high strength martensite or bainite. If the amount of C is less than 0.5%, the above effect is poor. On the other hand, if it exceeds 1.5%, it binds to Cr contained to form a passive oxide film and improve the corrosion resistance of the base. As a result, Cr carbide precipitates in the matrix, resulting in a decrease in the Cr concentration in the matrix and a decrease in corrosion resistance. For this reason, the amount of C in the whole composition is 0.5 to 1.5%. If such C is given as a solid solution in the above-mentioned iron alloy powder, the hardness of the iron alloy powder increases and the compressibility of the raw material powder is remarkably impaired, so the whole amount is given in the form of graphite powder.

The wear-resistant sintered alloy of the present invention is obtained by compacting a raw material powder in which a hard phase forming powder is added to an iron alloy powder and a graphite powder as described above into a desired shape and then sintering the powder. Can
The composition of the iron alloy powder is, by mass ratio, Ni: 1 to 3% by mass, Mo: 0.5 to 2% by mass, Cr: 0.1 to 1% by mass, Mn: 0.1 to 0.5% by mass. %, The balance is composed of Fe and inevitable impurities, and the composition of the hard phase forming powder is, by mass ratio, Mo: 15 to 35%, Si: 1 to 10%, Cr: 10 to 40%, and the balance Is composed of Co and inevitable impurities, and the addition amount is 15 to 45%, and the addition amount of graphite powder is 0.5 to 1.5%. Therefore, the wear-resistant sintered alloy of the present invention The total composition is in a mass ratio, and the overall composition is Cr: 1.58-18.55% by mass, Ni: 0.54-2.54% by mass, Mo: 2.67-16.84% by mass, Si: 0.15-4.5 mass%, Co: 2.25-33.30 mass%, Mn: 0.05-0.42 mass%, C: 0.5- .5% by weight, and the balance of Fe and unavoidable impurities. In addition, the metal structure is inevitable with the composition of Mo: 15 to 35%, Si: 1 to 10%, Cr: 10 to 40% and the balance of Co in the Fe-Ni-Mo-C alloy base. The hard phase consisting of impurities is dispersed by 15 to 45%.

  In the wear-resistant sintered alloy of the present invention, conventional machinability improving techniques can be applied. That is, at least one of lead powder, molybdenum disulfide powder, manganese sulfide powder, boron nitride powder, magnesium metasilicate-based mineral powder, and calcium fluoride powder, which is a machinability improving substance, is added to the raw material powder as 0.3. Addition of ˜2% may further disperse the machinability improving substance in the pores and grain boundaries of the wear-resistant sintered alloy. These are machinability improving components, and by dispersing them in the base, they become a starting point for chip breaking during cutting, and the machinability of the sintered alloy can be improved. If the content of these machinability improving components is less than 0.3%, the effect is insufficient, and if the content exceeds 2%, the strength of the sintered alloy decreases.

  Further, the pores of the wear-resistant sintered alloy of the present invention may be filled with one of lead, lead alloy, copper, copper alloy, and acrylic resin by infiltration or impregnation. When cutting a sintered alloy with pores, it becomes intermittent cutting, and the impact to the cutting edge of the tool is intermittently generated, but by containing lead, copper, etc. in the pores in this way, it becomes continuous cutting, and the cutting edge of the tool The shock to is reduced. Lead or lead alloy functions as a solid lubricant, and copper or copper alloy has a high thermal conductivity, thereby preventing heat accumulation and reducing damage to the blade edge due to heat. In addition, the acrylic resin has a function as a starting point for chip breaking.

[First embodiment]
An iron alloy powder comprising Ni: 2%, Mo: 1%, Cr: 0.5%, Mn: 0.3%, and the balance consisting of Fe and inevitable impurities, a hard phase forming powder having the powder composition shown in Table 1, and Prepare graphite powder, add 35% hard phase forming powder and 1% graphite powder to iron alloy powder, mix 100 parts by mass of mixed powder and 0.8 parts by mass of zinc stearate as molding lubricant. The raw material powder obtained by mixing was molded into a ring of φ30 mm × φ20 mm × h10 mm at a molding pressure of 650 MPa. Next, these compacts were sintered in an ammonia decomposition gas atmosphere at 1160 ° C. for 60 minutes to prepare samples Nos. 01 to 06. These samples were subjected to a simple wear test and a corrosion test. The results of these tests are also shown in Table 1.

The simple wear test was performed in a state in which impact and sliding inputs were applied at high temperatures. Specifically, the ring-shaped test piece (sintered alloy) was processed into a valve seat shape having a 45 ° tapered surface at the inner peripheral edge, and press-fitted into an aluminum alloy housing. Then, a disk-shaped mating material (valve) having a 45 ° taper surface on a part of the outer peripheral edge made of SUH-36 material is moved by piston movement by rotating an eccentric cam driven by a motor. The taper surfaces of the gold and the counterpart material were repeatedly collided. That is, the valve operation was performed by moving the piston up and down by repeating the opening operation of separating from the valve seat by the eccentric cam rotated by the motor drive and the seating operation on the valve seat by the valve spring. In this test, the temperature of the counterpart material was set by heating with a burner so that the sintered alloy would be 300 ° C., the number of impacts was 3000 times / minute, and the repetition time was 15 hours. After such a test, the wear amount of the valve seat and the wear amount of the valve were measured and evaluated. Further, in the corrosion test, after the ring-shaped test piece prepared by immersing 1 hour in a 10% nitric acid aqueous solution, by measuring the weight change before and after immersion, the corrosion weight loss divided by the this surface area (mg / cm ²⁾ As an evaluation.

  From Table 1, the influence of the Cr amount in the hard phase forming powder (the Cr amount in the hard phase) can be examined. The sample of sample number 01 has poor corrosion resistance due to the small amount of Cr in the hard phase forming powder, and the corrosion weight loss is large. Further, since the amount of Cr is scarce, the base of the sintered alloy is not sufficiently strengthened and the wear amount of the valve seat is also increased. However, in the sample of sample number 02 in which the amount of Cr in the hard phase forming powder is 10%, the corrosion weight loss is suppressed by the effect of improving the corrosion resistance by Cr, and the wear amount of the valve seat is also significantly reduced by strengthening the base by Cr. ing. Further, when the Cr content in the hard phase forming powder is up to 40%, the wear amount of the valve seat becomes a low value as the Cr content increases, and the corrosion weight loss tends to be suppressed low. Further, in the sample of sample number 06 in which the Cr amount in the hard phase forming powder exceeds 40%, the hardness of the hard phase forming powder increases due to the increase in the Cr amount in the hard phase forming powder. As a result of a decrease in compressibility and a decrease in the density of the molded body, the density of the sintered body has decreased, so the amount of wear of the valve seat has increased and the corrosion weight loss has increased remarkably. Furthermore, the wear powder of the valve seat attacks the valve, and the amount of wear of the valve is also significantly increased. From the above results, when the amount of Cr in the hard phase forming powder (the amount of Cr in the hard phase) is in the range of 10 to 40%, the wear amount of the valve seat and the valve is reduced, and the corrosion loss of the sintered alloy is also reduced. It was confirmed.

[Second Embodiment]
Iron alloy powder (Fe-2% Ni-1% Mo-0.5% Cr-0.3% Mn powder) used in the first example, hard phase forming powder (Co-30) used in sample number 04 of the first example % Cr-20% Mo-17% Fe-3% Si powder), and graphite powder, and as shown in Table 2, the addition ratio of the hard phase forming powder was changed and mixed to 100 parts by mass of the mixed powder. Further, 0.8 parts by mass of zinc stearate as a molding lubricant was blended, and the raw material powder obtained by mixing was molded and sintered in the same manner as in the first example to prepare samples Nos. 07-11. did. These samples were evaluated for wear resistance and corrosion resistance in the same manner as in the first example. The results are shown in Table 2 together with the value of the sample No. 04 of the first example.

  From Table 2, the influence of the addition amount of hard phase forming powder (the amount of hard phase dispersed in the matrix) can be examined. Sample No. 07, in which the addition amount of the hard phase forming powder is less than 15%, has a small amount of the hard phase, cannot suppress the plastic flow of the base, and has a large wear amount of the valve seat. Moreover, since the hard phase is scarce, Cr diffusing from the hard phase to the base becomes scarce, so the corrosion weight loss is large. However, in the sample of Sample No. 08 in which the addition amount of the hard phase forming powder is 15%, the hard phase improves the wear resistance and corrosion resistance of the base of the sintered alloy, and the wear amount of the valve seat is remarkably lowered and the corrosion weight loss is reduced. Has fallen. Further, when the addition amount of the hard phase forming powder is up to 35%, the wear amount and the corrosion weight loss of the valve seat tend to decrease as the addition amount of the hard phase forming powder increases. And, in the sample of Sample No. 10 where the addition amount of the hard phase forming powder is 45%, the compressibility of the raw material powder is reduced by increasing the addition amount of the hard phase forming powder. Although there is a tendency to increase slightly, both the amount of wear and the weight loss of the valve seat are still low. On the other hand, in the sample of Sample No. 11 in which the addition amount of the hard phase forming powder exceeds 45%, the influence of the compressibility decrease is significant, the wear amount of the valve seat is remarkably increased, and the corrosion weight loss is increased. Furthermore, the wear powder of the valve seat attacks the valve, and the amount of wear of the valve is remarkably increased. From the above results, it was confirmed that the amount of wear of the valve seat and the valve becomes small when the addition amount of the hard phase forming powder (the amount of the hard phase dispersed in the matrix) is in the range of 15 to 45%.

[Third embodiment]
The iron alloy powder having the composition shown in Table 3, the hard phase forming powder (Co-30% Cr-20% Mo-17% Fe-3% Si powder) used in Sample No. 04 of the first example, and the graphite powder Using 35% hard phase forming powder and 1% graphite powder to iron alloy powder, and mixing 100 parts by mass of mixed powder with 0.8 parts by mass of zinc stearate as a forming lubricant, and mixing The raw material powder obtained was molded and sintered in the same manner as in the first example to prepare samples Nos. 12 to 20. These samples were evaluated for wear resistance and corrosion resistance in the same manner as in the first example. The results are shown in Table 3 together with the value of sample No. 04 of the first example.

  The effects of the amount of Ni in the iron alloy powder can be examined by using samples Nos. 04 and 12 to 15 in Table 3. Sample No. 12 using an iron alloy powder not containing Ni does not reinforce the Fe base of the sintered alloy, has a large wear amount of the valve seat, and has a large corrosion weight loss. However, in the samples of Sample Nos. 13, 04, and 14 in which the amount of Ni in the iron alloy powder is 1 to 3%, the wear amount of the valve seat is remarkably reduced due to the effect of strengthening the Fe base by Ni and improving the corrosion resistance. The corrosion resistance of the base has been improved and the corrosion weight loss has been reduced. However, in the sample of Sample No. 15 where the amount of Ni in the iron alloy powder exceeds 3%, the compressibility of the raw material powder decreases due to the increase in the hardness of the iron alloy powder, and the compressibility of the raw material powder decreases. As a result of the decrease in the density of the molded body, the amount of wear and the weight loss of the valve seat are remarkably increased due to the decrease in the density of the sintered body. From the above results, it was confirmed that when the amount of Ni in the iron alloy powder is in the range of 1 to 3%, the wear amount of the valve seat becomes small and the corrosion weight loss is suppressed.

  The influence of the Cr amount in the iron alloy powder can be examined by the samples Nos. 04 and 16 to 20 in Table 3. Sample No. 16 using iron alloy powder containing no Cr does not strengthen the Fe base of the sintered alloy, has a large wear amount of the valve seat, and has a large corrosion weight loss. However, in the samples of Sample Nos. 18, 04 and 19 in which the Cr amount in the iron alloy powder is 0.1 to 1%, the wear amount of the valve seat is remarkably reduced due to the effect of improving the strengthened corrosion resistance of the Fe base by Cr, The corrosion resistance of the Fe base is improved and the corrosion weight loss is reduced. However, in the sample of Sample No. 20 in which the amount of Cr in the iron alloy powder exceeds 1%, the compressibility of the raw material powder decreases due to the increase in the hardness of the iron alloy powder, and the compressibility of the raw material powder decreases. As a result of the decrease in the density of the molded body, the amount of wear and the weight loss of the valve seat are remarkably increased due to the decrease in the density of the sintered body. From the above results, it was confirmed that when the amount of Cr in the iron alloy powder is in the range of 0.1 to 1%, the wear amount of the valve seat is reduced and the corrosion weight loss is suppressed.

[Fourth embodiment]
Iron alloy powder (Fe-2% Ni-1% Mo-0.5% Cr-0.3% Mn powder) used in the first example, hard phase forming powder (Co-30) used in sample number 04 of the first example % Cr-20% Mo-17% Fe-3% Si powder) and graphite powder, and further mixed into 100 parts by mass of the mixed powder obtained by mixing and mixing the graphite powder at different ratios as shown in Table 4. 0.8 parts by mass of zinc stearate as a lubricant was blended, and the raw material powder obtained by mixing was molded and sintered in the same manner as in the first example to prepare samples Nos. 21 to 26. These samples were evaluated for wear resistance in the same manner as in the first example. The results are shown in Table 4 together with the value of the sample No. 04 of the first example.

  From Table 4, the influence of the added amount of graphite powder (the amount of C in the entire composition) can be examined. In the sample No. 21 in which the amount of graphite powder added is less than 0.5%, the Fe base of the sintered alloy is not sufficiently strengthened, and the wear amount of the valve seat is large. However, in the sample of Sample No. 22 in which the added amount of graphite powder is 0.5%, the Fe base of the sintered alloy is strengthened, and the wear amount of the valve seat is remarkably reduced. Further, when the addition amount of the graphite powder is up to 1.0%, the valve seat wear amount tends to decrease as the addition amount of the graphite powder increases. In addition, in samples with an addition amount of graphite powder of 1.0 to 1.5%, the Fe base of the sintered alloy becomes hard and brittle, the valve seat wear amount increases, and the valve wear amount tends to increase slightly. However, the total wear amount still shows a value that does not cause a problem in practice. On the other hand, in the sample No. 26 in which the amount of graphite powder added exceeds 1.5%, the above tendency becomes more remarkable, the amount of wear of the valve seat increases remarkably, and the wear powder of the valve seat attacks the valve. As a result, the amount of wear on the valve has also increased significantly. From the above results, it was confirmed that the amount of wear of the valve seat and the valve becomes small when the amount of graphite powder added (the amount of C in the entire composition) is in the range of 0.5 to 1.5%.

[Fifth embodiment]
The iron alloy powder (Fe-2% Ni-1% Mo-0.5% Cr-0.3% Mn powder) used in the first example, the graphite powder, and the sample number 04 of the first example as shown in Table 5 Using the hard phase forming powder used (Co-30% Cr-20% Mo-17% Fe-3% Si powder) and the hard phase forming powder with a different ratio of Co and Fe, 35% of the forming powder and 1% of the graphite powder were added, and 100 parts by mass of the mixed powder was further mixed with 0.8 parts by mass of zinc stearate as a molding lubricant. Samples Nos. 27 to 32 were produced by molding and sintering in the same manner as in Example 1. These samples were evaluated for wear resistance in the same manner as in the first example. The results are shown in Table 5 together with the value of the sample No. 04 of the first example.

  From Table 5, the influence of the substitution rate of Fe when Co in the hard phase forming powder is replaced with Fe (the percentage of the Fe amount in the hard phase forming powder with respect to the total amount of Co and Fe in the hard phase forming powder) Can be examined. Sample No. 27 does not replace Co in the hard phase forming powder with Fe, and has the least amount of wear in the examples so far and shows good wear resistance. Here, when Co in the hard phase forming powder is substituted with Fe and the substitution rate of Fe is increased, the amount of wear tends to increase. However, when the substitution rate of Fe is up to about 80% (samples 04, 28 to 30), the amount of wear is suppressed to a level that does not cause any practical problems. However, in the samples of Sample Nos. 31 and 32 in which the substitution rate of Fe is increased by more than about 80%, the effect of Co is poor and the wear amount is remarkably increased. From the above results, it is possible to replace Co in the hard phase forming powder with Fe, but the substitution rate of Fe when replacing Co in the hard phase forming powder with Fe should be 80% or less. Was confirmed. The substitution rate of Fe is more preferably about 60% or less.

[Sixth embodiment]
The iron alloy powder (Fe-2% Ni-1% Mo-0.5% Cr-0.3% Mn powder), graphite powder used in the first example, and the sample number 04 of the first example as shown in Table 6 The hard phase forming powder (Co-30% Cr-20% Mo-17% Fe-3% Si powder) containing different contents of Mn is used to form a hard phase in the iron alloy powder. 35% of the forming powder and 1% of the graphite powder were added, and 100 parts by mass of the mixed powder was further mixed with 0.8 parts by mass of zinc stearate as a molding lubricant. Samples Nos. 30 to 33 were produced by molding and sintering in the same manner as in Example 1. These samples were evaluated for wear resistance in the same manner as in the first example. The results are shown in Table 6 together with the value of the sample No. 04 of the first example.

  From Table 6, the effect of containing Mn in the hard phase forming powder (hard phase) can be examined. Compared with the sample No. 04 in which the hard phase forming powder does not contain Mn, in the samples No. 33 to 35 in which the hard phase forming powder contains 5% or less of Mn, the alloy base of the hard phase is strengthened by Mn. Thus, the wear amount of the valve seat is small. On the other hand, since the hard phase is strengthened, the wear amount of the valve tends to slightly increase as the Mn content increases. In the sample No. 36 containing Mn in the hard phase forming powder in excess of 5%, the hard phase forming powder becomes hard and the compressibility of the raw material powder is remarkably lowered, so that the wear amount of the valve seat is remarkably increased. At the same time, the wear powder of the valve seat attacks the valve, and the amount of wear of the valve is remarkably increased. From the above results, it was confirmed that by adding Mn to the hard phase forming powder, the wear resistance could be further improved, but the Mn content of the hard phase forming powder should be kept to 5% or less. .

[Seventh embodiment]
Iron alloy powder (Fe-2% Ni-1% Mo-0.5% Cr-0.3% Mn powder) used in the first example, hard phase forming powder (Co-30) used in sample number 04 of the first example % Cr-20% Mo-17% Fe-3% Si powder), graphite powder and nickel powder, 35% hard phase forming powder in iron alloy powder, 1% graphite powder and nickel powder in the ratio shown in Table 7 Was added to 100 parts by mass of the mixed powder and 0.8 parts by mass of zinc stearate as a molding lubricant, and the raw material powder obtained by mixing was molded and sintered in the same manner as in the first example. As a result, samples Nos. 37 to 43 were prepared. These samples were evaluated for wear resistance in the same manner as in the first example. The results are shown in Table 7 together with the value of the sample No. 04 of the first example.

  According to Table 7, when nickel powder is not added to the raw material powder and nickel powder is not added to the base and sample number 04 does not contain Ni, the nickel powder is added at 5% or less as in sample numbers 37 to 42. It can be seen that the amount of seat wear decreases and the total amount of wear decreases. However, in the sample of Sample No. 43 in which the amount of nickel powder added exceeds 5%, a large amount of Ni-rich austenite having low wear resistance remains in the base, and the wear resistance of the valve seat itself is low. The amount of wear on the valve seat decreases, the amount of hard martensite increases, the aggressiveness of the counterpart valve increases, the amount of valve wear increases, and the total amount of wear increases rapidly. It becomes. From this, it was confirmed that the addition of nickel powder is effective in improving the wear resistance, but the amount added should be limited to 5.0% or less.

[Eighth embodiment]
Iron alloy powder (Fe-2% Ni-1% Mo-0.5% Cr-0.3% Mn powder) used in the first example, hard phase forming powder (Co-30) used in sample number 04 of the first example % Cr-20% Mo-17% Fe-3% Si powder), graphite powder and copper powder, 35% hard phase forming powder, 1% graphite powder and copper powder in the ratio shown in Table 8 Was added to 100 parts by mass of the mixed powder and 0.8 parts by mass of zinc stearate as a molding lubricant, and the raw material powder obtained by mixing was molded and sintered in the same manner as in the first example. As a result, samples Nos. 44 to 50 were prepared. These samples were evaluated for wear resistance in the same manner as in the first example. The results are shown in Table 8 together with the value of the sample No. 04 of the first example.

  According to Table 8, when copper powder is not added to the raw material powder, but less than 5% of copper powder is added as in the sample numbers 44 to 49 as compared with the sample number 04 which does not contain Cu in the base, the valve It can be seen that the amount of seat wear decreases and the total amount of wear decreases. However, in the sample of Sample No. 50 in which the amount of copper powder added exceeds 5%, the free copper phase cannot be completely dissolved in the matrix and the free copper phase is dispersed. As the amount increases, the amount of hard martensite increases, the aggressiveness of the counterpart valve increases, the amount of valve wear increases, and the total amount of wear increases rapidly. From this, it was confirmed that the addition of copper powder is effective in improving the wear resistance, but the amount added should be limited to 5.0% or less.

Claims (14)

In terms of mass ratio, the overall composition was Cr: 1.58 to 18.55 mass%, Ni: 0.54 to 2.54 mass%, Mo: 2.67 to 16.84 mass%, Si: 0.15 4.5 mass%, Co: 2.25 to 33.30 mass%, Mn: 0.05 to 0.42 mass%, C: 0.5 to 1.5 mass%, and the balance from Fe and inevitable impurities Become
In the Fe-Ni-Mo-C alloy base,
The composition is characterized by exhibiting a metal structure in which Mo: 15 to 35%, Si: 1 to 10%, Cr: 10 to 40%, and the balance of the hard phase composed of Co and inevitable impurities is dispersed by 15 to 45%. Wear-resistant sintered alloy.   The wear-resistant sintered alloy according to claim 1, wherein a part of the Co is substituted with Fe in the composition of the hard phase.   3. The wear-resistant firing according to claim 1, wherein Mn: 5% by mass or less is added to the composition of the hard phase so that Mn is 2.25% by mass or less in the overall composition. Bond money.   The Ni-Mo-C-based alloy base further contains Ni in an amount of 5.0% by mass or less based on the entire composition. Wear-resistant sintered alloy.   The Fe-Ni-Mo-C-based alloy base further contains Cu in an amount of 5.0% by mass or less based on the entire composition. Wear-resistant sintered alloy.   At least one machinability improving substance powder selected from the group consisting of lead, molybdenum disulfide, manganese sulfide, boron nitride, calcium metasilicate mineral, calcium fluoride is added to the pores and grain boundaries of the sintered alloy. The wear-resistant sintered alloy according to any one of claims 1 to 5, further dispersed by 3 to 2% by mass.   The wear resistance according to any one of claims 1 to 6, wherein pores of the sintered alloy are filled with one of lead, lead alloy, copper, copper alloy, and acrylic resin. Sintered alloy.   Composition is mass ratio, Ni: 1-3 mass%, Mo: 0.5-2 mass%, Cr: 0.1-1 mass%, Mn: 0.1-0.5 mass%, balance is Fe And a hard phase formed of an iron alloy powder composed of unavoidable impurities and a mass ratio of Mo: 15 to 35%, Si: 1 to 10%, Cr: 10 to 40%, and the balance of Co and unavoidable impurities Powder: 15 to 45% and graphite powder: 0.5 to 1.5% are added, the mixed raw material powder is compacted into a desired shape, and the resulting compact is sintered. A method for producing a wear-resistant sintered alloy.   The method for producing a wear-resistant sintered alloy according to claim 8, wherein a part of the Co in the hard phase forming powder is replaced with Fe.   The method for producing a wear-resistant sintered alloy according to claim 8 or 9, wherein the hard phase forming powder further contains Mn: 5 mass% or less. The method for producing a wear-resistant sintered alloy according to any one of claims 8 to 10, wherein 5% by mass or less of nickel powder is further mixed with the mixed powder. The method for producing a wear-resistant sintered alloy according to any one of claims 8 to 11, wherein 5% by mass or less of copper powder is further mixed with the mixed powder.   The raw material powder is 0 powder of at least one machinability improving substance selected from the group consisting of lead powder, molybdenum disulfide powder, manganese sulfide powder, boron nitride powder, calcium metasilicate mineral powder, and calcium fluoride powder. The method for producing a wear-resistant sintered alloy according to any one of claims 8 to 12, further comprising 3 to 2% by mass.   9. The pores of the wear-resistant sintered alloy obtained by the sintering are infiltrated or impregnated with any of lead, lead alloy, copper, copper alloy, and acrylic resin. 14. A method for producing a wear-resistant sintered alloy according to any one of 13 above.