MULTILAYERED SLIDING MEMBER

Abstract

A multilayered sliding member 1 comprises a backing plate 2 having a steel plate; and a porous sintered alloy layer 3 which is integrally joined to one surface of the backing plate 2 and is composed of 25 to 60% by mass of nickel, 2 to 7% by mass of phosphorus, and the balance copper.

Claims

1. A multilayered sliding member comprising: a backing plate having a steel plate; and a porous sintered alloy layer which is integrally joined to one surface of said backing plate and is composed of 25 to 60% by mass of nickel, 2 to 7% by mass of phosphorus, and the balance copper.

2. A multilayered sliding member comprising: a backing plate having a steel plate; and a porous sintered alloy layer which is integrally joined to one surface of said backing plate and is composed of 25 to 60% by mass of nickel, 2 to 7% by mass of phosphorus, 3 to 8% by mass of tin, and the balance copper.

3. The multilayered sliding member according to claim 1, wherein the steel plate is formed of a ferritic, austenitic, or martensitic stainless steel plate, and the one surface of said backing plate is one surface of the stainless steel plate.

4. The multilayered sliding member according to claim 1, wherein the steel plate is formed of a ferritic, austenitic, or martensitic stainless steel plate, said backing plate further has a nickel coating covering one surface of the stainless steel plate, and the one surface of said backing plate is one surface of the nickel coating.

5. The multilayered sliding member according to claim 1, wherein the steel plate is formed of a rolled steel plate for general structure or a cold rolled steel plate, said backing plate further has a nickel coating covering one surface of the rolled steel plate for general structure or the cold rolled steel plate, and the one surface of said backing plate is one surface of the nickel coating.

6. The multilayered sliding member according to claim 1, wherein said porous sintered alloy layer includes a matrix containing a copper-nickel alloy and a nickel-phosphorus alloy phase crystallized at grain boundaries of the matrix, and wherein the matrix has a micro Vickers hardness (HMV) of at least 170, and the nickel-phosphorus alloy phase has a micro Vickers hardness (HMV) of at least 600.

7. The multilayered sliding member according to claim 1, further comprising a coating layer filled in the pores of, and secured on one surface of, said porous sintered alloy layer and containing a synthetic resin.

8. The multilayered sliding member according to claim 7, wherein the synthetic resin includes at least one synthetic resin selected from a fluororesin, a polyacetal resin, a polyamide resin, a polyphenylene sulfide resin, a polyetheretherketone resin, and a polyamideimide resin.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] FIG. 1 is an explanatory vertical cross-sectional view of a preferred embodiment of a multilayered sliding member in accordance with the present invention;

[0029] FIG. 2 is an explanatory vertical cross-sectional view of another preferred embodiment of the multilayered sliding member in accordance with the present invention;

[0030] FIG. 3 is an explanatory diagram of a micrograph of a porous sintered alloy layer of the multilayered sliding member in accordance with Example 1;

[0031] FIG. 4 is an explanatory diagram of a micrograph of the porous sintered alloy layer of the multilayered sliding member in accordance with Example 3;

[0032] FIG. 5 is an explanatory diagram of a micrograph of the porous sintered alloy layer of the multilayered sliding member in accordance with Example 5; and

[0033] FIG. 6 is an explanatory perspective view for explaining a thrust test.

MODE FOR CARRYING OUT THE INVENTION

[0034] Next, a more detailed description will be given of the present invention and a mode for carrying it out on the basis of the preferred examples shown in the drawings. It should be noted that the present invention is not limited to these examples.

[0035] First, a description will be given of an example of the method of manufacturing a multilayered sliding member 1 in accordance with the present invention as shown in FIG. 1.

[0036] As a backing plate 2, a stainless steel plate is prepared which is constituted of a continuous strip with a thickness of 0.3 to 1.0 mm and is provided as a hoop material by being wound into a coil shape. The stainless steel plate to be prepared may not necessarily be a continuous strip, but may be a strip cut into an appropriate length.

[0037] The following are prepared: an electrolytic copper powder passing through a 150-mesh (97 m) sieve, an electrolytic nickel powder passing through a 250-mesh (60 m) sieve, an atomized copper-nickel alloy powder of copper and 25 to 40 mass % of nickel passing through a 200-mesh (74 m) sieve, an atomized nickel-phosphorus alloy powder of nickel and 4 to 11 mass % of phosphorus passing through a 350-mesh (44 m) sieve, an atomized copper-phosphorus alloy powder of copper and 15 mass % of phosphorus passing through a 350-mesh (44 m) sieve, and an atomized tin powder passing through a 350-mesh (44 m) sieve. These powders are used in combination, as required, and adjustment is made such that the compounding ratio becomes 25 to 60 mass % of nickel, 2 to 7 mass % of phosphorus, and the balance copper, or 25 to 60 mass % of nickel, 2 to 7 mass % of phosphorus, 3 to 8 mass % of tin, and the balance copper. Subsequently, these powders are charged into a V-type mixer and are mixed for 20 to 60 minutes to thereby prepare a mixed powder.

[0038] This mixed powder is sprayed onto one surface of the backing plate 2 into a uniform thickness and the backing plate 2 thus treated is sintered for 5 to 10 minutes at a temperature of 870 to 950 C. in a heating furnace set in a vacuum or adjusted to a reducing atmosphere of such as a hydrogen gas, a hydrogen-nitrogen mixed gas (25 vol. % H.sub.2 and 75 vol. % N.sub.2), or an ammonia cracked gas (AX gas: a mixed gas of 75 vol. % H.sub.2 and 25 vol. % N.sub.2). Through this sintering, it is possible to obtain the multilayered sliding member 1 in which a porous sintered alloy layer 3 containing 25 to 60 mass % of nickel, 2 to 7 mass % of phosphorus, and the balance copper, or 25 to 60 mass % of nickel, 2 to 7 mass % of phosphorus, 3 to 8 mass % of tin, and the balance copper, is integrally diffusion-bonded to one surface of the backing plate 2.

[0039] It was observed by a microscope that the porous sintered alloy layer 3 was comprised of a matrix containing a soft copper-nickel alloy exhibiting a hardness (HMV) of 170 or more and a hard nickel-phosphorus alloy phase dispersedly crystallized at grain boundaries of this matrix and exhibiting a hardness (HMV) of 600 or more

[0040] A description will be given of an example of the method of manufacturing a multilayered sliding member 1a which further has a coating layer 4, as shown in FIG. 2, on such a porous sintered alloy layer 3.

[0041] A petroleum-based solvent in an amount of 15 to 30 parts by weight is compounded with 100 parts by weight of a mixture containing a polytetrafluoroethylene resin, a barium sulfate, a phosphate, and a resin consisting of one or two or more kinds of organic materials, which mixture is obtained by agitating and mixing by a Henschel mixer 5 to 40 mass % of a barium sulfate, 1 to 30 mass % of a phosphate, 1 to 10 mass % of a resin consisting of one or more kinds of organic materials selected from a polyimide resin, a sintered phenolic resin, and a polyphenylene sulfide resin, and the balance a polytetrafluoroethylene resin. The compounded admixture is mixed at a temperature (15 C.) not more than the room-temperature transition point of the polytetrafluoroethylene resin to thereby fabricate a synthetic resin. This fabricated synthetic resin is supplied to and spread over one surface of the porous sintered alloy layer 3 and is rolled by a roller to obtain a predetermined thickness of the synthetic resin and allow the synthetic resin to be filled and secured into the pores of, and onto the one surface of, the porous sintered alloy layer 3. Subsequently, the semi-processed product thus treated is held for several minutes in a hot air drying furnace heated to a temperature of 200 to 250 C. to remove the solvent, and is then subjected to pressure roller treatment under a pressure of 300 to 600 kgf/cm.sup.2 to form the dried synthetic resin into a predetermined thickness. This semi-processed product is introduced into the heating furnace and is sintered by being heated at a temperature of 360 to 380 C. for a period between several minutes and 10 and several minutes, and is then removed out of the furnace and is subjected to roller treatment again to adjust the variation of the size. The multilayered sliding member 1a is thereby obtained which is provided with the coating layer 4 filled in the pores of, and secured on one surface of, the porous sintered alloy layer 3 which is integrally diffusion-bonded to one surface of the backing plate 2.

[0042] Hereafter, a description will be given of Examples 1 to 8 and Comparative Examples 1 and 2.

Example 1

[0043] A 0.65 mm-thick ferritic stainless steel plate (SUS 430) cut into a 170 mm width and a 600 mm length was used as the backing plate 2.

[0044] In order to reduce satellites from an alloy powder (25 mass % nickel, 3 mass % phosphorus, and 72 mass % copper), which was obtained by powdering by a gas atomizing method a molten alloy obtained by melting 55% by mass of a copper powder, 25% by mass of a nickel powder, and 20% by mass of a copper-15 mass % phosphorus alloy powder, the alloy powder was subjected to frictional grinding by using a roller mill and was classified to thereby obtain an alloy powder passing through a 200-mesh sieve.

[0045] This alloy powder was sprayed into a uniform thickness onto one surface of the backing plate 2 degreased and cleaned in advance with trichlene, and the backing plate 2 thus treated was sintered for 10 minutes at a temperature of 910 C. in the heating furnace adjusted to a reducing atmosphere of a hydrogen-nitrogen mixed gas (25 vol. % H.sub.2-75 vol. % N.sub.2), thereby obtaining a multilayered sliding member 1 having the backing plate 2 and the porous sintered alloy layer 3 which was integrally diffusion-bonded to one surface of the backing plate 2, had a thickness of a 0.3 mm, and was composed of 25% by mass of nickel, 3% by mass of phosphorus, and the balance copper. As is clear from FIG. 3, the porous sintered alloy layer 3 in the fabricated multilayered sliding member 1 showed a structure in which sintering due to the mutual diffusion of nickel and copper had progressed, and a nickel-phosphorus alloy phase 6 was dispersedly crystallized at grain boundaries of a matrix 5 containing a dense copper-nickel alloy. The hardness of the matrix 5 showed 174, and the hardness of the nickel-phosphorus alloy phase 6 showed 629.

Example 2

[0046] A backing plate similar to that of Example 1 was used.

[0047] In the same way as in Example 1, a copper alloy powder (30 mass % nickel, 3 mass % phosphorus, and 67 mass % copper) was prepared from 75% by mass of a copper-40 mass % nickel alloy powder, 20% by mass of a copper-15 mass % phosphorus alloy powder, and 5% by mass of a copper powder.

[0048] In the same way as in Example 1, excepting that this copper alloy powder was sintered at a temperature of 900 C., a multilayered sliding member 1 having the backing plate 2 and the porous sintered alloy layer 3 was fabricated. The porous sintered alloy layer 3 in the fabricated multilayered sliding member 1 exhibited a structure similar to that of Example 1. The hardness of the matrix containing the copper-nickel alloy showed 214, and the hardness of the nickel-phosphorus alloy phase showed 630.

Example 3

[0049] The backing plate 2 used was one which was provided with a 20 m-thick nickel coating by electrolytic nickel plating on the entire surfaces including both surfaces of a ferritic stainless steel plate (SUS 430) similar to that of Example 1.

[0050] A mixed powder (37.8 mass % nickel, 2.2 mass % phosphorus, and 60 mass % copper) was prepared from 80% by mass of a copper-25 mass % nickel alloy powder and 20% by mass of a nickel-11 mass % phosphorus alloy powder.

[0051] One surface of the nickel coating provided on one surface of the ferritic stainless steel plate (SUS 430) between the nickel coatings provided on the ferritic stainless steel plate (SUS 430) was degreased and cleaned by trichlene, and the prepared mixed powder was sprayed into a uniform thickness onto the one degreased and cleaned nickel coating to thereby fabricate a multilayered sliding member 1 having the backing plate 2 and the porous sintered alloy layer 3 in the same way as in Example 2. As is clear from FIG. 4, in the fabricated multilayered sliding member 1, the porous sintered alloy layer 3 which was integrally diffusion-bonded to the one surface of the nickel coating of the backing plate 2 showed a structure in which sintering due to the mutual diffusion of nickel and copper had progressed, and the nickel-phosphorus alloy phase 6 was dispersedly crystallized at grain boundaries of the matrix 5 containing a dense copper-nickel alloy. The hardness of the matrix 5 showed 222, and the hardness of the nickel-phosphorus alloy phase 6 showed 632.

Example 4

[0052] A backing plate 2 similar to that of Example 3 was used.

[0053] A mixed powder (40 mass % nickel, 3.5 mass % phosphorus, and 56.5 mass % copper) was prepared from 43.5% by mass of a nickel-8 mass % phosphorus alloy powder and 56.5% by mass of a copper powder.

[0054] In the same way as in Example 3, a multilayered sliding member 1 having the backing plate 2 and the porous sintered alloy layer 3 was fabricated from this mixed powder. In the fabricated multilayered sliding member 1, the porous sintered alloy layer 3 which was integrally diffusion-bonded to the one surface of the nickel coating of the backing plate 2 showed a structure in which sintering due to the mutual diffusion of nickel and copper had progressed, and the nickel-phosphorus alloy phase was dispersedly crystallized at grain boundaries of the matrix containing a dense copper-nickel alloy. The hardness of the matrix showed 243, and the hardness of the nickel-phosphorus alloy phase showed 633.

Example 5

[0055] A backing plate 2 similar to that of Example 3 was used excepting that a cold rolled steel plate (SPCC) was used in substitution of the ferritic stainless steel plate (SUS 430).

[0056] In the same way as in Example 1, a copper alloy powder (50 mass % nickel, 3 mass % phosphorus, and 47 mass % copper) was prepared from a 30% by mass of a copper powder, 50% by mass of a nickel powder, and 20% by mass of a copper-15 mass % phosphorus alloy powder.

[0057] In the same way as in Example 1, excepting that this copper alloy powder was sintered at a temperature of 895 C., a multilayered sliding member 1 having the backing plate 2 and the porous sintered alloy layer 3 was fabricated. As is clear from FIG. 5, in the fabricated multilayered sliding member 1, the porous sintered alloy layer 3 which was integrally diffusion-bonded to the one surface of the nickel coating of the backing plate 2 showed a structure in which sintering due to the mutual diffusion of nickel and copper had progressed, and the nickel-phosphorus alloy phase 6 was dispersedly crystallized at grain boundaries of the matrix 5 containing a dense copper-nickel alloy. The hardness of the matrix 5 showed 259, and the hardness of the nickel-phosphorus alloy phase 6 showed 636.

Example 6

[0058] A backing plate 2 similar to that of Example 5 was used.

[0059] A mixed powder (57.6 mass % nickel, 2.4 mass % phosphorus, and 40 mass % copper) was prepared from 60% by mass of a nickel-4 mass % phosphorus alloy powder and 40% by mass of a copper powder.

[0060] In the same way as in Example 3, a multilayered sliding member 1 having the backing plate 2 and the porous sintered alloy layer 3 was fabricated from this mixed powder. The porous sintered alloy layer 3 in the fabricated multilayered sliding member 1 showed a structure in which sintering due to the mutual diffusion of nickel and copper had progressed, and the nickel-phosphorus alloy phase was dispersedly crystallized at grain boundaries of the matrix containing a dense copper-nickel alloy. The hardness of the matrix showed 262, and the hardness of the nickel-phosphorus alloy phase showed 639.

Example 7

[0061] A backing plate 2 similar to that of Example 1 was used.

[0062] A mixed powder (35.6 mass % nickel, 4.4 mass % phosphorus, 6 mass % tin, and 54 mass % copper) was prepared from 40% by mass of a nickel-II mass % phosphorus alloy powder, 6% by mass of tin powder, and 54% by mass of a copper powder.

[0063] In the same way as in Example 3, a multilayered sliding member 1 having the backing plate 2 and the porous sintered alloy layer 3 was fabricated from this mixed powder. In the fabricated multilayered sliding member 1, the porous sintered alloy layer 3 which was integrally diffusion-bonded to the one surface of backing plate 2 showed a structure in which sintering due to the mutual diffusion of nickel and copper had progressed, and the nickel-phosphorus alloy phase was dispersedly crystallized at grain boundaries of the matrix containing a dense copper-nickel alloy. Tin in the porous sintered alloy layer 3 was alloyed with copper in the matrix and formed a copper-tin alloy. The hardness of the matrix showed 237, and the hardness of the nickel-phosphorus alloy phase showed 633.

Example 8

[0064] Fifteen mass percent of barium sulfate, 10% by mass of calcium pyrophosphate, 2% by mass of a polyimide resin, 0.5% by mass of graphite, and the balance a polytetrafluoroethylene resin were supplied into a Henschel mixer and were agitated and mixed, and 20 parts by weight of a petroleum-based solvent was compounded with 100 parts by weight of the resultant mixture. A synthetic resin obtained by mixing this admixture at a temperature (15 C.) not more than the room-temperature transition point of the PTFE was supplied to and spread over one surface of the porous sintered alloy layer 3 of a multilayered sliding member 1 similar to that of Example 1 and was rolled by a roller to allow the synthetic resin to be filled and secured into the pores of, and onto the one surface of, the porous sintered alloy layer 3. Subsequently, after the semi-processed product thus treated was held for 5 minutes in a hot air drying furnace heated to a temperature of 200 C. to remove the solvent, the dried synthetic resin was rolled under a pressure of 400 kgf/cm.sup.2 by a roller to form a 0.05 mm-thick coating layer 4 in the pores of, and on the one surface of, the porous sintered alloy layer 3. This semi-finished product was heated and sintered in the heating furnace at 370 C. for 10 minutes, and was subjected to pressurizing treatment by the roller again to make dimensional adjustment and correction of waviness and the like. A multilayered sliding member 1a was thereby obtained in which a 0.3 mm-thick porous sintered alloy layer 3 composed of 25% by mass of nickel, 3% by mass of phosphorus, and the balance copper was integrally diffusion-bonded to the one surface of backing plate 2, and which was provided with the coating layer 4 composed of 15% by mass of barium sulfate, 10% by mass of calcium pyrophosphate, 2% by mass of a polyimide resin, 0.5% by mass of graphite, and the balance a polytetrafluoroethylene resin in the pores of, and on the one surface of, the porous sintered alloy layer 3.

Comparative Example 1

[0065] A mixed powder obtained by mixing 10 wt. % of an atomized tin powder passing through a 350-mesh sieve and 90% by mass of an electrolytic copper powder passing through a 150-mesh sieve for 20 minutes by a V-type mixer was sprayed into a uniform thickness onto the one surface of the backing plate 2 similar to that of Example 5. After this semi-finished product was sintered for 10 minutes at a temperature of 860 C. in the heating furnace adjusted to a hydrogen gas atmosphere, thereby fabricating a multilayered sliding member 1 in which the porous sintered alloy layer 3 having a thickness of a 0.3 mm and composed of 10% by mass of tin and the balance copper was integrally diffusion-bonded to one surface of the backing plate 2.

Comparative Example 2

[0066] A multilayered sliding member 1a was fabricated which had a 0.05 mm-thick coating layer 4 constituted of a synthetic resin similar to that of Comparative Example 8 and filled and secured in the pores of, and on the one surface of, the porous sintered alloy layer 3 of the multilayered sliding member 1 similar to that of Comparative Example 1.

[0067] A test was conducted on sulfidation corrosion resistance and friction and wear characteristics with respect to the multilayered sliding members 1 and 1a of the above-described Examples 1 to 8 and Comparative Examples 1 and 2.

Test Method Concerning Sulfidation Corrosion Resistance

[0068] ENEOS Gear Oil GL-5 (tradename) manufactured by JXTG Nippon Oil & Energy Corporation was used as a gear oil with an excellent extreme pressure additive, metal corrosion inhibitor, detergent dispersant, and the like added to a base oil. This gear oil was accommodated in a container, the multilayered sliding members 1 and 1a of the above-described Examples 1 to 8 and Comparative Examples 1 and 2 were immersed for 500 hours in this gear oil held at a temperature of 150 C., and were removed every 100 hours to measure the mass change rate (%) of the porous sintered alloy layer 3 of each of the multilayered sliding members 1 and 1a.

Test Conditions and Test Method Concerning the Coefficient of Friction and the Amount of Wear

Test Conditions:

[0069] Velocity: 1.3 m/min [0070] Load (bearing pressure): 200 to 800 kgf/cm.sup.2 [0071] Test period: 20 hrs. [0072] Mating member: Carbon steel for machine structural use (S45C) [0073] Lubrication: Oil (tradename: Daphne Super Multi Oil #32 manufactured by Idemitsu Kosan Co., Ltd.) medium condition

Test Method:

[0074] As shown in FIG. 6, a square plate-like bearing test piece 11 having a side length of 30 mm and fabricated from each of the multilayered sliding members 1 and 1a of Examples 1 to 8 and Comparative Examples 1 and 2 was fixed to a test stand. While a predetermined load was being applied from a cylindrical body 12 serving as a mating member to one surface 13 of the plate-like bearing test piece 11 in a direction A perpendicular to the one surface 13, the cylindrical body 12 was rotated in a direction B about an axis 14 of the cylindrical body 12, and measurement was made of the coefficient of friction between the plate-like bearing test piece 11 and the cylindrical body 12 and the amount of wear of the surface 13 after testing for 20 hours.

[0075] The test results are shown in Tables 1 to 3.

TABLE-US-00001 TABLE 1 Examples 1 2 3 4 Backing plate SUS 430 SUS 430 SUS 430 SUS 430 Presence or absence of nickel coating absent absent present present Components of porous sintered alloy layer: mass % Nickel (Ni) 25 30 37.8 40 Phosphorus (P) 3 3 2.2 3.5 Tin (Sn) Copper (Cu) 72 67 60 56.5 Presence or absence of coating layer absent absent absent absent Hardness (MHV) of matrix 174 214 222 222 Hardness (MHV) of nickel- 629 630 632 632 phosphorus alloy phase Mass change rate (%) 100 hrs. 0.32 0.28 0.22 0.21 200 hrs. 0.38 0.28 0.31 0.22 300 hrs. 0.38 0.28 0.35 0.22 400 hrs. 0.41 0.28 0.35 0.23 500 hrs. 0.41 0.28 0.35 0.24 Coefficient of friction Bearing (bearing pressure kgf/cm.sup.2) pressure 200 0.10-0.12 0.09-0.12 0.09-0.10 0.09-0.12 300 0.10-0.12 0.09-0.12 0.09-0.11 0.09-0.12 400 0.11-0.13 0.10-0.12 0.09-0.12 0.09-0.10 500 0.11-0.13 0.10-0.12 0.10-0.12 0.09-0.10 600 0.12-0.14 0.12-0.14 0.10-0.12 0.09-0.10 700 0.12-0.14 0.12-0.14 0.11-0.14 0.09-0.10 800 0.12-0.14 0.12-0.14 0.11-0.14 0.09-0.11 Amount of wear (mm) 200 0.005 0.005 0.005 0.008 (bearing pressure kgf/cm.sup.2) 300 0.006 0.006 0.005 0.008 400 0.006 0.008 0.007 0.010 500 0.008 0.008 0.008 0.010 600 0.009 0.010 0.010 0.015 700 0.013 0.012 0.012 0.015 800 0.013 0.013 0.012 0.017

TABLE-US-00002 TABLE 2 Examples 5 6 7 8 Backing plate SPCC SPCC SUS 430 SUS 430 Presence or absence of nickel coating present present absent absent Components of porous sintered alloy layer: mass % Nickel (Ni) 50 57.6 35.6 25 Phosphorus (P) 3 2.4 4.4 3 Tin (Sn) 6 Copper (Cu) 47 40 54 72 Presence or absence of coating layer absent absent absent present Hardness (MHV) of matrix 259 262 237 174 Hardness (MHV) of nickel- 636 639 633 629 phosphorus alloy phase Mass change rate (%) 100 hrs. 0.20 0.18 0.22 0.21 200 hrs. 0.20 0.18 0.28 0.22 300 hrs. 0.22 0.18 0.30 0.22 400 hrs. 0.22 0.19 0.30 0.23 500 hrs. 0.22 0.20 0.34 0.24 Coefficient of friction Bearing (bearing pressure kgf/cm.sup.2) pressure 200 0.08-0.10 0.07-0.09 0.08-0.10 0.02-0.04 300 0.08-0.10 0.07-0.09 0.09-0.10 0.02-0.05 400 0.09-0.11 0.08-0.10 0.09-0.11 0.02-0.06 500 0.10-0.12 0.08-0.10 0.10-0.12 0.02-0.06 600 0.10-0.12 0.08-0.10 0.10-0.12 0.03-0.08 700 0.10-0.13 0.08-0.12 0.11-0.14 0.03-0.08 800 0.10-0.13 0.08-0.12 0.11-0.14 0.04-0.09 Amount of wear (mm) 200 0.003 0.002 0.003 0.012 (bearing pressure kgf/cm.sup.2) 300 0.005 0.004 0.003 0.014 400 0.009 0.004 0.006 0.016 500 0.009 0.005 0.006 0.016 600 0.010 0.006 0.008 0.018 700 0.010 0.008 0.008 0.018 800 0.010 0.009 0.010 0.024

TABLE-US-00003 TABLE 3 Comparative Examples 1 2 Backing plate SPCC SPCC Presence or absence of nickel coating present present Components of porous sintered alloy layer: mass % Nickel (Ni) Phosphorus (P) Tin (Sn) 10 10 Copper (Cu) 90 90 Presence or absence of coating layer absent present Hardness (MHV) of matrix Hardness (MHV) of nickel- phosphorus alloy phase Mass change rate (%) 100 hrs. 18 200 hrs. 18 300 hrs. 20 400 hrs. 20 500 hrs. 20 Coefficient of friction Bearing (bearing pressure kgf/cm.sup.2) pressure 200 0.26-0.36 0.18-0.20 Amount of wear (mm) 200 0.18 0.12 (bearing pressure kgf/cm.sup.2)

[0076] As for the multilayered sliding member 1 in Comparative Example 1, since the coefficient of friction showed 0.36 under the condition of the bearing pressure of 200 kgf/cm.sup.2 in the test concerning the coefficient of friction and the amount of wear (thrust test), the test at higher bearing pressure conditions was suspended. In addition, in the multilayered sliding member 1a of Example 8, a defect such as exfoliation attributable to the sulfidation corrosion of the porous sintered alloy layer 3 was not observed in the coating layer 4. Meanwhile, as for the multilayered sliding member 1a of Comparative Example 2, it was observed that sulfides (CuS, etc.) due to sulfidation corrosion were generated in spots in the coating layer 4 on the one surface after immersion for 100 hours in the gear oil containing an extreme pressure additive, so that a further test was suspended.

[0077] From the test results shown in Tables 1 and 2, it can be appreciated that, in the test on sulfidation corrosion resistance due to immersion in the gear oil containing an extreme pressure additive, the multilayered sliding members 1 and 1a in accordance with the present invention make it possible to inhibit the progress of sulfidation corrosion, and exhibit excellent sliding characteristics and substantially improved load resistance even under a high bearing pressure condition of 800 kgf/cm.sup.2.

DESCRIPTION OF REFERENCE NUMERALS

[0078] 1, 1a: multilayered sliding member [0079] 2: backing plate [0080] 3: porous sintered alloy layer [0081] 4: coating layer