Sintered alloy superior in wear resistance

Abstract

A sintered bearing has a structure in which NiP alloy particles having an average diameter of 10 to 100 m are dispersed in an amount of 1 to 20% by mass in a Cu-based sintered alloy base, a FeCu-based sintered alloy base or a CuNi-based sintered alloy base. The NiP alloy particles are derived from a raw material powder comprising 1 to 12% by mass of P; and a remainder composed of Ni and inevitable impurities. The Cu-based sintered alloy base contains no less than 40% by mass of Cu. The FeCu-based sintered alloy base contains no more than 50% by mass of Fe. The CuNi-based sintered alloy base contains 20 to 40% by mass of Ni and 0.1 to 1.0% by mass of P; or contains 10 to 25% by mass of Ni, 10 to 25% by mass of Zn and 0.1 to 1.0% by mass of P.

Claims

1. A Cu-based sintered alloy having a structure in which NiP alloy particles having an average diameter of 10 to 100 m are dispersed in an amount of 1 to 20% by mass in a Cu-based sintered alloy base that contains no less than 40% by mass of Cu and selectively contains 0.2 to 8% by mass of a solid lubricant, wherein said NiP alloy particles are derived from a raw material powder comprising 1 to 12% by mass of P; and a remainder composed of Ni and inevitable impurities.

2. The Cu-based sintered alloy according to claim 1, wherein said Cu-based sintered alloy base contains 5 to 15% by mass of Sn; and a remainder composed of Cu and inevitable impurities.

3. The Cu-based sintered alloy according to claim 1, wherein said Cu-based sintered alloy base contains 5 to 15% by mass of Sn; 0.1 to 1.0% by mass of P; and a remainder composed of Cu and inevitable impurities.

4. The Cu-based sintered alloy according to claim 1, wherein said Cu-based sintered alloy base contains 3 to 13% by mass of Sn; 2 to 12% by mass of Zn; and a remainder composed of Cu and inevitable impurities.

5. The Cu-based sintered alloy according to claim 1, wherein said Cu-based sintered alloy base contains 1 to 15% by mass of Sn; 8 to 30% by mass of Fe; and a remainder composed of Cu and inevitable impurities.

6. The Cu-based sintered alloy according to claim 1, wherein said Cu-based sintered alloy base contains 1 to 15% by mass of Sn; 8 to 30% by mass of Fe; 0.1 to 1.0% by mass of P; and a remainder composed of Cu and inevitable impurities.

7. The Cu-based sintered alloy according to claim 1, wherein said solid lubricant is at least any one selected from the group consisting of graphite, molybdenum disulfide, boron nitride and calcium fluoride.

8. A FeCu-based sintered alloy having a structure in which NiP alloy particles having an average diameter of 10 to 100 m are dispersed in an amount of 1 to 20% by mass in a FeCu-based sintered alloy base that contains no larger than 50% by mass of Fe and selectively contains 0.2 to 8% by mass of a solid lubricant, wherein said NiP alloy particles are derived from a raw material powder comprising 1 to 12% by mass of P; and a remainder composed of Ni and inevitable impurities.

9. The FeCu-based sintered alloy according to claim 8, wherein said FeCu-based sintered alloy base contains 0.5 to 5% by mass of Sn; and a remainder composed of Cu and inevitable impurities.

10. The FeCu-based sintered alloy according to claim 8, wherein said FeCu-based sintered alloy base contains 0.5 to 5% by mass of Sn; 0.1 to 1.0% by mass of P; and a remainder composed of Cu and inevitable impurities.

11. The FeCu-based sintered alloy according to claim 8, wherein said FeCu-based sintered alloy base contains 0.5 to 5% by mass of Sn; 0.5 to 5% by mass of Zn; and a remainder composed of Cu and inevitable impurities.

12. The FeCu-based sintered alloy according to claim 8, wherein said FeCu-based sintered alloy base contains 0.5 to 5% by mass of Sn; 0.5 to 5% by mass of Zn; 0.1 to 1.0% by mass of P; and a remainder composed of Cu and inevitable impurities.

13. The FeCu-based sintered alloy according to claim 8, wherein said solid lubricant is at least any one selected from the group consisting of graphite, molybdenum disulfide, boron nitride and calcium fluoride.

14. A CuNi-based sintered alloy having a structure in which NiP alloy particles having an average diameter of 10 to 100 m are dispersed in an amount of 1 to 20% by mass in a CuNi-based sintered alloy base that contains 20 to 40% by mass of Ni, 0.1 to 1.0% by mass of P and a remainder composed of Cu and inevitable impurities; and selectively contains 0.2 to 8% by mass of a solid lubricant, wherein said Ni-P alloy particles are derived from a raw material powder comprising 1 to 12% by mass of P; and a remainder composed of Ni and inevitable impurities.

15. The CuNi-based sintered alloy according to claim 14, wherein said solid lubricant is at least any one selected from the group consisting of graphite, molybdenum disulfide, boron nitride and calcium fluoride.

16. A CuNi-based sintered alloy having a structure in which NiP alloy particles having an average diameter of 10 to 100 m are dispersed in an amount of 1 to 20% by mass in a CuNi-based sintered alloy base that contains 10 to 25% by mass of Ni, 10 to 25% by mass of Zn, 0.1 to 1.0% by mass of P and a remainder composed of Cu and inevitable impurities; and selectively contains 0.2 to 8% by mass of a solid lubricant, wherein said NiP alloy particles are derived from a raw material powder comprising 1 to 12% by mass of P; and a remainder composed of Ni and inevitable impurities.

17. The CuNi-based sintered alloy according to claim 16, wherein said solid lubricant is at least any one selected from the group consisting of graphite, molybdenum disulfide, boron nitride and calcium fluoride.

18. An FeCu-based sintered alloy having a structure in which NiP alloy particles having an average diameter of 10 to 100 m are dispersed in an amount of 1 to 20% by mass in a FeCu based sintered alloy base, wherein the FeCu based sintered alloy base comprises 48 to 83% by mass of Fe and a remainder composed of Cu and inevitable impurities, and selectively comprises at least any one of; 5 to 5% by mass of Sn, 0.5 to 5% by mass of Zn, 0.1 to 1.0% by mass of P, and 0.2 to 8% by mass of a solid lubricant, and the NiP alloy particles are derived from a raw material powder comprising 1 to 12% by mass of P; and a remainder composed of Ni and inevitable impurities.

19. The FeCu-based sintered alloy according to claim 18, wherein the solid lubricant is at least any one selected from the group consisting of graphite, molybdenum disulfide, boron nitride and calcium fluoride.

Description

DETAILED DESCRIPTION OF THE INVENTION

BEST MODE FOR CARRYING OUT THE INVENTION

(1) A Cu-based sintered alloy of the present invention has a structure where NiP alloy particles of an average diameter of 10 to 100 m are dispersed in an amount of 1 to 20% by mass in a Cu-based sintered alloy base that contains Cu in an amount of no less than 40% by mass and selectively contains a solid lubricant in an amount of 0.2 to 8% by mass. Particularly, the NiP alloy particles are derived from a raw material powder containing P in an amount of 1 to 12% by mass; and a remainder composed of Ni and inevitable impurities.

(2) The Cu-based sintered alloy base may contain Sn in an amount of 5 to 15% by mass and a remainder composed of Cu and inevitable impurities; Sn in the amount of 5 to 15% by mass, P in an amount of 0.1 to 1.0% by mass and the remainder composed of Cu and inevitable impurities; Sn in an amount of 3 to 13% by mass, Zn in an amount of 2 to 12% by mass and the remainder composed of Cu and inevitable impurities; Sn in an amount of 1 to 15% by mass, Fe in an amount of 8 to 30% by mass and the remainder composed of Cu and inevitable impurities; or Sn in the amount of 1 to 15% by mass, Fe in the amount of 8 to 30% by mass, P in the amount of 0.1 to 1.0% by mass and the remainder composed of Cu and inevitable impurities.

(3) The solid lubricant may be at least any one of graphite, molybdenum disulfide, boron nitride and calcium fluoride.

(4) An FeCu-based sintered alloy of the preset invention has a structure where NiP alloy particles of the average diameter of 10 to 100 m are dispersed in the amount of 1 to 20% by mass in a FeCu-based sintered alloy base that contains Fe in an amount of no more than 50% by mass and selectively contains a solid lubricant in the amount of 0.2 to 8% by mass. Particularly, the NiP alloy particles are derived from a raw material powder containing P in the amount of 1 to 12% by mass; and a remainder composed of Ni and inevitable impurities.

(5) The FeCu-based sintered alloy base may contain Sn in an amount of 0.5 to 5% by mass and a remainder composed of Cu and inevitable impurities; Sn in the amount of 0.5 to 5% by mass, P in the amount of 0.1 to 1.0% by mass and the remainder composed of Cu and inevitable impurities; Sn in the amount of 0.5 to 5% by mass, Zn in the amount of 0.5 to 5% by mass and the remainder composed of Cu and inevitable impurities; or Sn in the amount of 0.5 to 5% by mass, Zn in the amount of 0.5 to 5% by mass, P in the amount of 0.1 to 1.0% by mass and the remainder composed of Cu and inevitable impurities.

(6) The solid lubricant may be at least any one of graphite, molybdenum disulfide, boron nitride and calcium fluoride.

(7) A CuNi-based sintered alloy of the present invention has a structure where NiP alloy particles of the average diameter of 10 to 100 m are dispersed in the amount of 1 to 20% by mass in a CuNi-based sintered alloy base that contains Ni in an amount of 20 to 40% by mass, P in the amount of 0.1 to 1.0% by mass and a remainder composed of Cu and inevitable impurities and selectively contains a solid lubricant in the amount of 0.2 to 8% by mass; or a structure where NiP alloy particles of the average diameter of 10 to 100 m are dispersed in the amount of 1 to 20% by mass in a CuNi-based sintered alloy base that contains Ni in an amount of 10 to 25% by mass, Zn in the amount of 10 to 25% by mass, Pin the amount of 0.1 to 1.0% by mass and a remainder composed of Cu and inevitable impurities and selectively contains a solid lubricant in the amount of 0.2 to 8% by mass. Particularly, the NiP alloy particles are derived from a raw material powder containing P in the amount of 1 to 12% by mass; and a remainder composed of Ni and inevitable impurities.

(8) The solid lubricant may be at least any one of graphite, molybdenum disulfide, boron nitride and calcium fluoride.

(9) The Cu-based sintered alloy, FeCu-based sintered alloy and CuNi-based sintered alloy of the present invention improve a wear resistance by allowing the NiP alloy particles to be dispersed in the metal structures thereof. The NiP alloy particles are described in detail hereunder.

(10) (1) P Content of NiP Alloy Particle Component: 1 to 12% by Mass

(11) The closer an ingredient amount of P is to that of an Ni.sub.3P phase (15% P), the harder the NiP alloy particles are. Such NiP alloy particles contribute to an improvement in wear resistance of a sintered bearing when dispersed in the sintered alloys. However, the NiP alloy particles have a property where the closer the ingredient amount of P is to that of the Ni.sub.3P phase (15% P), the more brittle they become; and a less ingredient amount of P results in a decreased hardness. Hard and brittle NiP alloy particles can easily fall off the sintered alloys sliding along a shaft as a counterpart, thus actually leading to a significant wear. Meanwhile, a less ingredient amount of P results in a decreased hardness of the NiP alloy particles. This is not preferable because, in such case, the NiP alloy particles contribute less to improving the wear resistance even when dispersed in the sintered alloys. Therefore, the P content of the NiP alloy particles was set to be 1 to 12%.

(12) (2) Particle Diameter of NiP Alloy Particle: Average Particle Diameter of 10 to 100 m

(13) A size control needs to be performed on a NiP alloy powder for the purpose of satisfying both the hardness of the NiP alloy particles and an adhesiveness of the same to the bases, the NiP alloy particles being dispersed in the bases of the sintered alloys. When the average particle diameter of the NiP alloy particles is smaller than 10 m, it is difficult to control a reaction between the NiP alloy particles and the bases of the sintered alloys that takes place through sintering. This is not preferable because, in such case, P in the NiP alloy particles diffuses into the bases of the sintered alloys, thus causing the hardness and wear resistance of the NiP alloy particles to decrease. Further, when the average particle diameter of the NiP alloy particles is no less than 100 m, relatively less particles exist on a bearing bore surface. This is not preferable because, in such case, the wear resistance is decreased. Therefore, the average particle diameter of the NiP alloy particles was set to be 10 to 100 m.

(14) Here, the average particle diameter refers to a particle diameter that is measured using a laser diffraction particle size analyzer and expressed as a volume average particle diameter (Mv).

(15) (3) Additive Amount of NiP Alloy Particle: 1 to 20% by Mass

(16) Although there can be brought about the effect of improving the wear resistance by allowing the NiP alloy particles to be dispersed in the bases of the sintered alloys, this effect is low when the amount of the NiP alloy particles is smaller than 1%; and this effect is not recognizable when the NiP alloy particles are added in an amount of larger than 20%, which adversely and unfavorably results in a higher raw material cost. Therefore, the additive amount of the NiP alloy particles was set to be 1 to 20%.

(17) (4) Solid Lubricant: 0.2 to 8.0% by Mass when Contained

(18) The solid lubricant brings about a superior lubricity to a bearing and thus contributes to improving the wear resistance thereof. The solid lubricant contains at least one of graphite, molybdenum disulfide, boron nitride and calcium fluoride.

(19) Although the solid lubricant may be contained on an as-needed basis, there cannot be achieved the effect of improving the wear resistance if the solid lubricant contained is in an amount of smaller than 0.2%; and a significant decrease in strength occurs if the solid lubricant contained is in an amount of greater than 8%, both of which are not preferable.

(20) The Cu-based sintered alloy, FeCu-based sintered alloy and CuNi-based sintered alloy of the present invention can be obtained by adding and mixing into the entire raw material powder of the solid lubricant-containing sintered alloys the NiP alloy powder, in the ratio of 1 to 20% by mass, that has the average diameter of 10 to 100 m and contains P in the amount of 1 to 12% by mass and the remainder composed of Ni and inevitable impurities; performing powder compacting on a mixed powder thus prepared; and then sintering the same at a temperature not higher than a temperature near a melting point of the NiP alloy. For example, a melting point of a Ni-11% P alloy is 880 C., and the NiP particles will remain as particles in the structure without all being melted even if when sintered at a temperature comparatively higher than the melting point as long as a sintering time is as short as about 15 minutes. Thus, although it is preferred that the sintering temperature be not higher than the melting point of the NiP alloy, the sintering temperature does not strictly need to be the melting point of the NiP alloy or lower. That is, as long as the sintering time is short, the sintering temperature may be comparatively higher than the melting point of the NiP alloy. Here, although the melting point of NiP, when the P concentration is 11%, is also a eutectic point (880 C.), such melting point increases as the P concentration changes.

(21) The sintered alloy thus obtained is a sintered alloy with the NiP alloy particles that are derived from the NiP alloy powder dispersed therein. Further, the adhesiveness of the NiP alloy particles to the bases of the sintered alloys can be improved by optimizing sintering conditions such that an appropriate reaction can take place between the Cu component or the Ni component in the sintered alloys and the surfaces of the NiP alloy particles.

(22) Described hereunder are specific working examples of the Cu-based sintered alloy, FeCu-based sintered alloy and CuNi-based sintered alloy of the present invention. However, the present invention is not limited to the following working examples, but may employ various modified modes.

Working Example 1

(23) (1) Producing Cu-based Sintered Alloy, FeCu-based Sintered Alloy and CuNi-Based Sintered Alloy

(24) As raw material powders, there were prepared a Ni-11% P alloy powder of an average particle diameter of 35 m; an electrolytic Cu powder; an Sn powder; a CuSn powder; a CuP powder; a CuZn powder; a Fe powder; a CuNi powder; and a solid lubricant such as a graphite powder. These raw material powders were then combined to one another in accordance with compositions shown in Table 1 when producing Cu-based sintered alloys; compositions shown in Table 2 when producing FeCu-based sintered alloys; and compositions shown in Table 3 when producing CuNi-based sintered alloys. Zinc stearate was then added to the raw material powders thus combined in an amount of 0.5% before mixing the same through a V-type mixer for 20 minutes. The powders thus mixed were then press-molded under a given pressure of a range of 200 to 700 MPa to produce a ring-shaped powder compact. The powder compact thus produced was then sintered in an endothermic gas (endothermic-type gas) atmosphere at a given temperature of a range of 670 to 800 C. when producing the Cu-based sintered alloys; a given temperature of a range of 750 to 920 C. when producing the FeCu-based sintered alloys; and a given temperature of a range of 800 to 940 C. when producing the CuNi-based sintered alloys, the endothermic gas atmosphere being generated by passing a mixture of a natural gas and air through a heated catalyst such that a decomposition and conversion reaction could take place. Sizing was then performed to obtain the Cu-based sintered alloys, the FeCu-based sintered alloys and the CuNi-based sintered alloys. Next, these sintered alloys were impregnated with a lubricating oil.

(25) Through the aforementioned steps, produced were oil-impregnated bearings made of the Cu-based sintered alloys, FeCu-based sintered alloys and CuNi-based sintered alloys that have the compositions shown in Table 1 through Table 3, each oil-impregnated bearing being formed into the shape of a ring and a size of outer diameter: 18 mminner diameter: 8 mmheight: 4 mm.

(26) In Table 1 through Table 3, sintered alloys within the scope of the present invention are referred to as Invention examples, whereas those outside the scope of the present invention are referred to as Comparative examples.

(27) TABLE-US-00001 TABLE 1 Cu-based sintered alloy Amount of Maximum NiP alloy worn depth Base composition (% by mass) powder added of sintered Category No. Cu Sn P Zn Fe C MoS.sub.2 (% by mass) alloy(mm) Invention 1 Remainder 9 0 0 0 0 0 10 0.012 example 2 Remainder 10 0 0 0 1 0 8 0.012 3 Remainder 9 0 0 0 4 0 5 0.008 4 Remainder 9 0.2 0 0 7 0 2 0.004 5 Remainder 5 0 10 0 0 0 18 0.010 6 Remainder 5 0 10 0 7 0 4 0.007 7 Remainder 9 0 3 0 0 0 10 0.009 8 Remainder 9 0.4 0 0 0.5 3 5 0.004 9 Remainder 10 0.4 0 0 0 0 12 0.010 10 Remainder 11 0.4 0 0 1.5 0 10 0.005 11 Remainder 11 0 0 10 0.7 0 10 0.007 12 Remainder 9 0.4 0 10 0.5 0 8 0.009 13 Remainder 3 0 0 27 0 0 5 0.007 Comparative 1 Remainder 9 0 0 0 0 0 0 0.048 example 2 Remainder 10 0 0 0 1 0 0 0.037 3 Remainder 9 0 0 0 4 0 0.5 0.024 4 Remainder 9 0.2 0 0 7 0 0 0.020 5 Remainder 5 0 10 0 0 0 0 0.040 6 Remainder 5 0 10 0 7 0 25 0.052 7 Remainder 9 0 3 0 0 0 0 0.033 8 Remainder 9 0.4 0 0 0.5 3 0 0.020 9 Remainder 10 0.4 0 0 0 0 0 0.023 10 Remainder 11 0.4 0 0 1.5 0 0 0.021 11 Remainder 11 0 0 10 0.7 0 0 0.024 12 Remainder 9 0.4 0 10 0.5 0 0 0.022 13 Remainder 3 0 0 27 0 0 0 0.023

(28) TABLE-US-00002 TABLE 2 FeCu-based sintered alloy Amount of Maximum NiP alloy worn depth Base composition (% by mass) powder added of sintered Category No. Cu Fe Sn P Zn C MoS.sub.2 (% by mass) alloy (mm) Invention 14 Remainder 48 2 0 0 0 0 7 0.008 example 15 Remainder 48 2 0.3 0 0 0 10 0.003 16 Remainder 48 2 0 2 0 0 15 0.004 17 Remainder 48 2 0.4 2 0.5 0 8 0.006 18 Remainder 74 1.5 0 0 0 0 5 0.003 19 Remainder 77 1 0 0 2 0 2 0.002 20 Remainder 83 1 0 0 1 0 3 0.002 Comparative 14 Remainder 48 2 0 0 0 0 0 0.018 example 15 Remainder 48 2 0.3 0 0 0 25 0.030 16 Remainder 48 2 0 2 0 0 0 0.018 17 Remainder 48 2 0.4 2 0.5 0 0 0.015 18 Remainder 74 1.5 0 0 0 0 0.5 0.021 19 Remainder 77 1 0 0 2 0 0 0.014 20 Remainder 83 1 0 0 1 0 0 0.015

(29) TABLE-US-00003 TABLE 3 CuNi-based sintered alloy Amount of Maximum NiP alloy worn depth Base composition (% by mass) powder added of sintered Category No. Cu Ni P Zn C (% by mass) alloy (mm) Invention 21 Remainder 23 0.4 0 0 7 0.010 example 22 Remainder 23 0.4 0 7 10 0.006 23 Remainder 17 0.4 17 0 15 0.012 24 Remainder 17 0.4 17 4 8 0.009 Comparative 21 Remainder 23 0.4 0 0 0 0.023 example 22 Remainder 23 0.4 0 7 25 0.018 23 Remainder 17 0.4 17 0 0.5 0.037 24 Remainder 17 0.4 17 4 0 0.029
(2) Wear Resistance Test

(30) A wear resistance test was performed on the ring-shaped Cu-based sintered alloys, FeCu-based sintered alloys and CuNi-based sintered alloys (referred to as ring-shaped bearings hereunder) obtained. An S45C shaft was inserted into each ring-shaped bearing, and then rotated at a rate of 100 m/min for 200 hours while applying, from outside the ring-shaped bearing, a load of a bearing pressure of 1.5 MPa in a radial direction of the ring-shaped bearing (a direction orthogonal to an axial direction of the shaft). Later, a wear resistance was evaluated by measuring a maximum worn depth of a sliding surface of the ring-shaped bearing.

(31) The results thereof are shown in Table 1 through Table 3.

(32) The maximum worn depth of the ring-shaped bearing made of the Cu-based sintered alloy of each invention example was not lager than 0.015 mm; the maximum worn depth of the ring-shaped bearing made of the FeCu-based sintered alloy of each invention example was not lager than 0.008 mm; and the maximum worn depth of the ring-shaped bearing made of the CuNi-based sintered alloy of each invention example was not lager than 0.012 mm. That is, it was confirmed that the wear resistance of each sintered alloy had been improved by adding the NiP alloy particles. Further, it was also confirmed that the wear resistance tended to be higher when the solid lubricant had been added as compared to examples where no solid lubricant had been added.

(33) In contrast, the maximum worn depth of the ring-shaped bearing made of the Cu-based sintered alloy of each comparative example was 0.020 to 0.048 mm; the maximum worn depth of the ring-shaped bearing made of the FeCu-based sintered alloy of each comparative example was 0.015 to 0.030 mm; the maximum worn depth of the ring-shaped bearing made of the CuNi-based sintered alloy of each comparative example was 0.018 to 0.037 mm. That is, wear resistances significantly lower than those of the invention examples were confirmed regardless of whether or not the solid lubricant had been added.