GB2284640A

GB2284640A - Slide member

Info

Publication number: GB2284640A
Application number: GB9425982A
Authority: GB
Inventors: Yoshikazu Fujisawa; Makoto Tsuji; Takeshi Narishige; Takahiro Gunji; Kazuhisa Okamoto
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 1991-07-18
Filing date: 1992-07-20
Publication date: 1995-06-14
Anticipated expiration: 2012-07-20
Also published as: GB2284640B; GB9425982D0

Abstract

A slide member comprises a slide portion, the surface of which comprises an aggregate of crystals of a lead alloy having crystal planes directed towards said slide surface whereby to form at least part of said surface. The aggregate comprises first oriented crystals 13, having a (h00) plane directed towards said surface and, optionally, second oriented crystals having (111) and (222) planes directed towards said surface, crystal surfaces being provided by (h00) planes, the relative abundance of said first oriented crystals as determinable by X-ray diffractometry being at least 60% as expressed by the ratio I(a)/(I(a)+I(b)> where I(a) and I(b) are the integrated intensities for diffraction peaks correspondingly to the first and second oriented crystals respectively. Such slide members have improved properties in terms of wear resistance, strength, and seizure resistance. <IMAGE>

Description

SLIDE MEMBER This invention relates to a slide member, and more particularly, to a slide member the surface of which comprises a slide portion having a slide surface for engagement with a mating member.

There are conventional, knawn slide members such as a piston for an internai combustion engine, which has grooves formed on a base material of an Al alloy for receiving piston rings, wherein the groove is provided with a surface layer comprising a metal plating layer on an inner surface of the groove so as to improve the wear resistance of the groove; a piston for an internal combustion engine, which is provided with a surface layer comprising a metal plating layer on an outer surface of a skirt portion of a base material of an Al alloy, so as to improve the wear resistance of the skirt portion; and a slide bearing with a surface layer comprising a Pb alloy.

However, under existing circumstances where speed and output of the engine have tended to increase, the surface layer of the abovedescribed pistons suffers from poor wear resistance due to a low degree of hardness and strength.

The above-described slide bearing is applicable to a journal portion of a crankshaft, an enlarged end of a connecting rod or the like in an internal combustion engine. However under the abovedescribed circumstances, the surface layer of the prior art slide bearings suffers from the inability to retain sufficient oil and a poor seizure resistance due to an inferior initial conformability.

Viewed from one aspect the present invention provides a slide member having a slide portion having a slide surface for engagement with a mating member, the slide portion having a surface layer comprising metal crystals belonging to a cubic system having a high atomic density crystal plane directed towards said slide surface whereby to form at least part of said surface.

The crystal plane may be a close-packed plane of the metal crystal and the percentage area A of the close-packed plane in the slide surface, e.g. the percentage of the area of the plane of the slide surface which is constituted by such crystal surfaces, is preferably in the range of A 2 30 %.

In addition, the metal crystal may have a body-centred cubic structure , and the crystal plane may be a secondary slip plane. The percentage area B of the secondary slip plane in the slide surface is preferably in the range of B 2 50 2.

By providing a metal crystal structure having a surface layer as described above, a high degree of hardness of the surface layer can be achieved, thereby providing a slide member with an improved wear resistance and an improved strength.

In one preferred embodiment of the invention the surface layer of the slide portion comprises an aggregate of crystals of a lead alloy having (hOO] plane crystal surfaces. The aggregate comprises first oriented crystals and optionally second and third oriented crystals, the first being defined as those having an [hOO] plane (by Miller indices) directed toward the slide surface, the second as having [111] and (222] planes directed towards the slide surface and the third having planes other than [hOO), [111] or [222] directed towards the slide surface. The relative abundancies of the first, second and third oriented crystals can be determined by X-ray diffractometry by the ratios of the integrated intensities of the diffraction peaks for the different crystal types, I(a), I(b) and I(c) being the integrated intensities for the first, second and third oriented crystals respectively. I(b) and I(c) may be zero but I(a) is preferably 60% to 100% of the sum of I(a) and I(b) and I(c) is preferably no more than 20% of the sum of I(a), I(b) and I(c).

By specifying the metal crystal structure of the surface layer as described above, there is provided a slide member with an increased seizure resistance of the surface layer.

Thus, with slide members according to the invention not only is it possible to achieve a high degree of hardness of the surface layer by providing a specific metal crystal structure of the surface layer, thereby improving the wear resistance and the strength of the surface layer, but it is also possible to provide a slide member of this type wherein sufficient oil retention is achieved on the surface layer and the initial conformability of the surface layer can be improved by providing a specific metal crystal structure of the surface layer, thereby providing an increased seizure resistance of the surface layer.

Viewed from another aspect the invention also provides a slide member having a slide portion having a slide surface for engagement with a mating member, the slide portion having a surface layer comprising metal crystals belonging to a cubic system having a close-packed plane directed towards said slide surface whereby to form at least 30% of the area of said surface.

Viewed from a further aspect the invention also provides a slide member having a slide portion having a slide surface for engagement with a mating member, the slide portion having a surface layer comprising metal crystals having a bodycentred cubic structure having a secondary slip plane directed towards said slide surface whereby to form at least 50% of the area of said surface.

Viewed from a still further aspect the invention also provides a slide member having a slide portion having a slide surface for engagement with a mating member, the slide portion having a surface layer comprising an aggregate of crystals of a lead alloy having crystal planes directed towards said slide surface whereby to form at least part of said surface said aggregate comprising first oriented crystals having a [hOO] plane directed towards said slide surface and, optionally, second oriented crystals having [lll and [222] planes directed towards said surface, crystal surfaces being provided by [hOO] planes, the relative abundance of said first oriented crystals as determinable by X-ray diffractometry being at least 60% as expressed by the ratio I(a)/(I(a) + 1(b)) where I(a) and I(b) are the integrated intensities for diffraction peaks corresponding to the first and second oriented crystals respectively.

Viewed from a yet further aspect the invention also provides a slide member having a slide portion having a slide surface for engagement with a mating member, the slide portion having a surface layer comprising an aggregate of crystals of a lead alloy having crystal planes directed towards said slide surface whereby to form at least part of said surface said aggregate comprising first oriented crystals having a thOO] plane directed towards said slide surface and, optionally, second oriented crystals having [111] and [222] planes directed towards said surface and third oriented crystals having planes other than [hOO], [111] and (222] directed towards said surface, crystal surfaces being provided by (hOO] planes, the relative abundance of said third oriented crystals as determinable by X-ray diffractometry being no more than 20% as expressed by the ratio I(c)/(I(a) + I(b) + I(c)) where I(a), I(b) and I(c) are the integrated intensities for diffraction peaks corresponding to the first, second and third oriented crystals respectively.

Preferred embodiments of the invention will now be described by way of example and with reference to the accompanying drawings in which: Fig. 1 is a side view of a piston; Fig. 2 is an enlarged sectional view taken along a line 2-2 in Fig. 1; Fig 3A is a perspective view illustrating a close-packed plane of a face-centred cubic structure; Fig.3B is a perspective view illustrating a close-packed plane of a body-centered cubic structure; Fig.4A is an illustration for explaining the inclination of a close-packed plane of a face-centered cubic structure; Fig.4B is an illustration for explaining the inclination of a close-packed plane of a body-centered cubic structure; Fig.5 is an X-ray diffraction pattern for an Fe crystal in a surface layer; Fig.6 is a photomicro graph showing the sturcture of an Fe crystal in a slide surface; Fig.7 is an X-ray diffraction pattern for a Cr crystal in a surface layer; Fig.8 is an X-ray diffraction pattern for a Ni crystal in a surface layer; Fig.9 is a photanicro graph showing the structure of a Ni crystal in a slide surface; Fig.10 is a graph illustrating the relationship between the percentageareaAof a close-packed planeinthe slide surface and the hardness of thesurface layer; Fig.11 is a graph illustrating the relationship between the percentageareaAof a close-packed plane intheslide surface and the amount of wearofthesurface layer; Fig.12 is a side view of a piston; Fig.13 is an enlarged sectional view taken along a line 13-13 in Fig.12; Fig.14 is a perspective view illustrating a secondary slip plane of a body-centered cubic structure; Fig.15 is an illustration for explaining the inclination of a secondary slip plane of a body-centered cubic structure; Fig.16 is an X-ray diffraction pattern of an Fe crystal in a surface layer; Fig.17 is a photanicrograph showingtnestructure of the Fe crystal in a slide surface: Fig.18A is a graph illustrating the hardness of surface layers according to an embodiment of the invention and a comparative example; Fig. 18B is a graph illustrating the amount of wear of surface layers according to an embodiment of the invention and a comparative example; Fig.19A is a graph illustrating the density of cracks in surface layers according to an embodiment of the invention, a comparative example and a reference example; Fig.19B is a graph illustrating the strength of surface layers according to an embodiment the invention and a comparative example; Fig.20 is a plan view of a test piece; Fig.21 is an X-ray diffraction pattern of an Fe crystal in a surface layer in accordance with an embodiment of the invention; Fig.22 is a photanicrograph showing the structure of an Fe crystal in a slide surface in accordance with an embodiment of the invention; Fig.23 is an exploded plan view of a slide bearing; Fig.24 is an enlarged sectional view taken along a line 24-24 in Fig.23; Fig.25 is a schematic view of a portion of a slide surface in accordance with the invention; Fig.26 is a schematic longitudinal sectional view of a portion of a surface layer in accordance with the invention; Fig.27 is an illustration for explaining the measurement of the inclination angle of first oriented crystals; Fig.28 is an X-ray diffraction pattern of a Pb alloy crystal in a surface layer; Fig.29 is a photonicrograph showing a structure of a Pb alloy crystal in a slide surface; Fig.30 is a photanicrograph showing a structure of a Pb alloy crystal, taken through a longitudinal section of a surface layer; Fig.31 is a photcmicro graph showing a structure of a Pb alloy crystal in another slide surface; Fig.32 is a graph illustrating the relationship between the presence rate Ri of first oriented crystals and the surface pressure of the surface layer when seizure occurs; Fig.33 is a graph illustrating the relationship between the presence rate R2 of third oriented crystals and the surface pressure of the surface layer when seizure occurs.

Figs. 1 to 11 illustrate a first embodiment of the present invention.

Referring to Figs.l and 2, a piston 1, serving as a slide member for an internal combustion engine, has a base material 2 of an Al alloy, which has grooves 3 for receiving piston rings 5. A surface layer 4 is provided on an inner surface of the groove 3 of the base material 2. The surface layer 4 has a slide surface 4a in contact with the piston ring 5 serving as a mating member.

The surface layer 4 is formed by an electroplating process and comprises an aggregate of a metal crystal belonging to a cubic system, e.g. having a face-centred cubic strcture (hereinafter referred to as an fcc structure) or a body-centred cubic structure (hereinafter referred to as a bcc structure).

Metal crystals having an fcc structure are , for example, crystals such as Pb, Ni, Cu, Al, Ag, Au and the like.

Mental crystals having a bcc structure are , for example, crystals such as Fe, Cr, Mo, W; Ta, Zr, Nb, V and the like.

As shown in Fig.3A, a close-packed plane at in an fcc structure Sl is a (111) plane ( by Miller indices ) comprising six atoms. A close-packed plane al in a bcc structure Sz is a (110) plane ( by Miller indices ) comprising five atoms, as shown in Fig.3B.

Predeterminedly orientated crystals of such a metal have a close-packed plane a1 as a crystal surface of high atomic density directed towardsa slide surface 4a so as to form the slide surface. The percentage area Aofthe close-packed plane a1 in the slide surface 4a is set in the range of A 2 30 %.

Since the close-packed plane a1 is higher in atomic density than the other crystal surfaces, a high degree of hardness can be achieved in the slide surface 4a, namely the surface layer 4 by providing the percentage area A as described above. This leads to an improvement in the wear resistance. When the percentageareaAisless than 30 %, the hardness of the surface layer 4 deteriorates.

An inclination of the close-packed plane a1 to a phantom plane C extending along the slide surface 4a affects the wear resistance of the surface layer 4.

The inclination angle B of the close-packed plane a, of the fcc structure S with respect to a phantom plane C is preferably in the range of 0 5 0 < 20 as shown in Fig.4A. The inclination angle 8 of the close-packed plane al of the bcc structure S2 with respect to a phantom plane C is preferably in the range of 0 # # 20 as shown in Fig.

4B. When the inclination angle 8 becomes greater than 30 " , the wear resistance of the surface layer deteriorates.

Examples of preferred embodiments will be described below.

The inner surface of the annular recess 3 in the base material 2 of an Al alloy was subjected to an electroplating process so as to form a surface layer 4 comprising an aggregate of Fe crystals.

The conditions for the electroplating process were as follows: a plating bath of ferrous sulfate was used; the pH of the plating bath was 3 or less (constant); an additive of carbamide, boric acid, saccharin or ammonium sulfate was used: the temperature of the plating bath was 50 C and the current density of the cathode was 8 A/dm2.

Fig.5 is a pattern diagram of an X-ray diffraction for Fe crystals in the surface layer 4, wherein peak b1 indicates a plane (110) as the close-packed plane a1, and peak b2 indicates a plane (211). It can be seen from Fig.5 that there exist in the surface layer 4 Fe crystals which are oriented so that the close-packed plane a1 lies in a plane parallel to the phantom plane C extending along the slide surface 4a.

In this case, the higher the height of the peak b1 and thus the higher its integrated strength the more the orientation degree of the Fe crystals increases. This results in an increased percentage area A of the close-packed plane al in the slide surface 4a. The orientation degree is controlled by varying the conditions for the electroplating process. In Fig.5, the percentageareaAof the closepacked planes a1 in the slide surface 4a is equal to 30 % (A = 30 %).

The crystal structure of the Fe in the slide surface 4a is shown by an electron photcmicrograph (5,000 magnification ) in Fig.6.

Two base materials 2 were prepared. The inner surface of the groove 3 of one of the base materials 2 was subjected to an electroplating process so as to form a surface layer 4 comprising Cr crystals. A surface layer comprising Ni crystals was formed on the inner surface of the groove 3 of the other base material 2 in the same manner.

Fig.7 is a pattern diagram of an X-ray diffraction for the Cr crystals in the surface layer 4, wherein peak b, indicates a plane (110) as the close-packed plane a,. and peak b2 indicates a plane (211). In this case, a percentageareaAofthe close-packed planes a1 in the slide surface 4a is equal to 65 %.

Fig.8 is a pattern diagram of an X-ray diffraction for the Ni crystals in the surface layer 4, wherein peak b3 indicates a plane (111) as the close-packed plane a1, and peak b4 indicates a plane (200). In this case, a percentageareaAof the close-packed planes at in the slide surface 4a is equal to 65 %. The structure of the Ni crystal in the slide surface 4a is shown by an electron photonicrograph (5,000 magnification ) in Fig.9.

In the respective surface layers4 comprising the Fe crystals, the Cr crystals and the Ni crystals, inclination angles 8 of the close-packed plane a1 were in the range of 0 < 8 " 20 Fig.10 illustrates results of a hardness test for the respective surface layers4. A measurement of a micro Vickers hardness was conducted with a hypermicrophotometer under a load of 5 g. In Fig.10, line c1 indicates the result for the surface layer 4 comprising the Fe crystals, line C2 indicates the result for the surface layer 4 comprising the Cr crystals, and line C3 indicates the result for the surface layer 4 comprising the Ni crystals.

As is apparent from Fig.10, a hardness of the surface layer 4 can be improved by choosing the percentage area A of the close-packed planes at to be in teh range of 30 % or more.

Fig.11 illustrates results of a wear test for the respective surface layers 4. A measurement of the amount of wear was conducted with a tip-on-disk testing machine. The test conditions were as follows: the load on the disk was set at 10 kgf; the material of the disk was a nitrided carbon steel material (S48C material); the speed of revolution of the disk was set at 0.5 m/sec; and the sliding distance was 1000 m. Lines c1 to C3 in Fig.11 correspond to the lines ct to C3 in Fig.10, respectively.

As is apparent from Fig.ll,thewear resistance of the surface layer 4 can be improved by choosing the percentage area A of the closepacked planes a1 to be in the range of 30 % or more.

The improved technology of this invention in the above-described first embodiment is not limited to the above-described piston, but is also applicable to other slide members such as a pulley provided with a surface layer having a metal crystal such as Ni, Fe or Cr on a belt groove, a rocker arm for an internal combustion engine provided with a surface layer having a metal crystal such as Cr on a slipper, and a cam shaft for an internal combustion engine provided with a surface layer having a metal crystal such as Cr on a journal portion.

Figs.12 to 22 illustrate a second embodiment of the present invention.

Referring to Figs.12 and 13, a piston 1 for an internal combustion engine, serving as a slide member, has a base material 2 of an Al alloy. A surface layer 4 is provided on an outer surface of a skirt portion 6 of the piston 1 of base material 2. The surface layer 4 has a slide surface 4a in contact with an inner surface 7 of a cylinder bore (a mating member).

The surface layer 4 is formed by an electroplating process and comprises an aggregate of a metal crystal having a bcc structure.

Metal crystals having a bcc structure include , for example, crystals such as Fe, Cr, Mo, W, Ta, Zr, Nb, V and the like.

As shown in Fig.14, a primary slip plane and thus a close-packed plane a1 in the bcc structure Sz is a plane (110). The orientation d of slipisrepresented by the direction < 111 > . When a secondary slip plane is defined as a crystal surface which includes the orientation of slip of the crystal surface and is highest in atomic density except the close-packed plane ai, a secondary slip plane ae corresponds to a plane (211) or a plane (123). In the illustration, a plane (211) isrepresentedbythesecondary slip plane a2.

Predeterminedly orientated crystals of such a metal have a secondary slip plane a2 as a crystal plane higher in atomic density directed towards the slide surface 4a so as to form the slide surface. The percentage area B of the secondary slip planes az in the slide surface4aispreferably in the range of B2 50 %.

If the metal crystals are oriented in the above manner, a high degree of hardness can be achieved in the surface layer 4, thereby improving the wear resistance of the surface layer 4.

In addition, the density of cracks in the surface layer 4 is reduced and hence, in conjunction with the high degree of hardness, the strength of the surface layer 4 can be improved. In the metal crystal the orientation degree of the plane (211) as the secondary slip plane a2 and the orientation degree of the plane (110) as the close-packed plane a1 have a relationship such that the orientation degree of one of the planes decreases as the orientation degree of the other plane increases. In this case, as the orientation degree of the plane (110) increases, the density of cracks in the surface layer 4 tends to increase. Therefore it is very advantageous to increase the orientation degree of the plane (211) in order to improve the strength of the surface layer 4. When the percentage areaBbeccmes less than 50 %, the density of cracks in the surface layer 4 increases, thereby reducing the strength of the surface layer 4.

The inclination of the secondary slip plane a2 with respect to a phantom plane extending along the slide surface 4a affects the wear resistance of the surface layer 4. For this reason, the inclination angle a of the secondary slip plane az in the bcc structure S2 with respect to a phantom plane C is preferably in the range of 0 5 8 < 30 o as shown in Fig.15. When the inclination angle 8 becomes greater then 300, the wear resistance of the surface layer 4 deteriorates.

Examples of preferred embodiments now will be described.

The outer surface of a skirt portion 6 in a base material 2 of an Al alloy was subjected to an electroplating process so as to form a surface layer 4 comprising an aggregate of Fe crystals.

The conditions for the electroplating process were as follows: a plating bath of ferrous sulfate was used; the pH of the plating bath was 3 or less (constant); an additive of carbamide, boric acid, saccharin or ammonium sulfate was used; the temperature of the plating bath was 60 C; and the current density of the cathode was 8 A/dm2.

Fig.16 is a pattern diagram of an X-ray diffraction for the Fe crystals in the surface layer 4, wherein peak b1 indicates a plane (110) as the close-packed plane al, and a peak bz indicates a plane (211) as the secondary slip plane az. It can be seen from fig. 16 that Fe crystals present in the surface layer 4 are oriented so that the secondary slip plane az lies in a plane parallel to the phantom plane C extending along the slide surface 4a.

In this case, the higher the height of the peak b2 and thus the higher its integrated intensity , the more the orientation degree of the Fe crystal increases. This results in an increased percentageareaB of the secondary slip planes a2 in the slide surface 4a. The orientation degree is controlled by varying the conditions for the electroplating process. In Fig.16, the percentage area B of the secondary slip plane az in the slide surface 4a is equal to 98 X (B = 98 %). The structure of the Fe crystal in the slide surface 4a is shown by an electron photomicrcgraph (5,000 magnification ) in Fig.

17. The inclination angle 8 of the secondary slip plane a2 is in the range of 0 < 20 " 20 Fig.18A illustrates a comparison of the hardness of surface layers of the embodiment and a comparative example. Fig.18B illustrates a comparison of the amount of wear between the surface layers of the embodiment and a comparative example. The surface layer of the embodiment has a slide surface in which the percentage area B of the secondary slip planes az is equal to 98 %. In the surface layer of the comparative example, the crystal surface is oriented at random. A measurement of the amount of wear was conducted with a tipon-disk testing machine. The test conditions were as follows: the load on the disk was set at 10 kgf; the material of the disk was a nitride carbon steel material (S48C material); the speed of the revolution was set at 0.5 m/sec; and the sliding distance was 1000 m.

As is apparent from Figs.18A and 18B, the surface layer of the embodiment exhibits a higherdegree of hardness than the surface layer of the comparative example. As a result, the surface layer of the embodiment exhibits a superior wear resistance.

Fig.19A illustrates a comparison of the density of cracks of the surface layers of the embodiment, a comparative example and a reference example. Fig. 19B illustrates a comparison of the strength of the surface layers of the embodiment and a comparative example. The surface layers of the embodiment and the comparative example are the same as those in Figs.l8A and 18B. The surface layer of the reference- example is one in which the percentage area A of the close-packed planes a1 and thus the planes (110) in the slide surface is equal to 70 % and the percentage areaBof the secondary slip plane az is equal to 30 2.

strength is - measured by a tension test under the following conditions: Fig.20 shows a test piece 8 with an entire length L1= 50 mm; a width W1 at both ends= 10.5 mm; a length Lz between the shoulders= 32 mm; a length L3 of constant width= 18 mm; a width W2 of constant width= 6 mm; and a thickness of 20 gm. Such a test piece 8 of foil was obtained by the process of first forming a test piece of the same structure as the surface layer 4 by subjecting an electroplating process on a stainless plate of the same dimension as of the test piece, and separating the test piece 8 from the stainless plate. The tensile rate is 20 mm/min under ambient temperature.

As is apparent from Figs.19A and l9B, the surface layer of the embodiment exhibits an extremely low density of cracks compared to the surface layer of the comparative example. However, the surface layer of the embodiment is superior to the surface layer of the comparative example in strength. The superior strength is caused not only by the low density of cracks, butalsobythehigh degree of hardness.

It should be noted from Fig.19A that the density of cracks increases in the surface layer of the reference example due to an incresase in the orientation degree of the plane (110).

Fig.21 is a pattern diagram of an X-ray diffraction for Fe crystals in the surface layer 4 of another example, wherein peak b1 indicates a plane (110) as the close-packed plane ai, and peak b2 indicates a plane (211) as the secondary slip plane a2. In this case, the percentagearea s ofthesecondary slip plane a2 in the slide surface 4a is equal to 53 % (B = 53 2). The structure of the Fe crystal in the slide surface 4a is shown by an electron photanicrcgraph (5,000 magnification ) in Fig.22. The inclination angle 8 of the secondary slip plane a2 is in the range of O" < 6 < 20 It should be noted that the improved technology of this invention in the above-described second embodiment is not limited to the abovedescribed piston, but is also applicable to other slide members such as an intake or an exhaust valve of an internal combustion engine provided with a surface layer on a stem portion, a rocker shaft for an internal combustion engine provided with a surface layer on a portion to be supported, and a cam shaft for an internal combustion engine provided with a surface layer on a journal portion.

Figs.23 to 33 illustrate a third embodiment of the present invention.

Referring to Figs.23 and 24, a slide bearing 9 as a slide member is applicable to a journal portion of a crankshaft in an engine, an enlarged end of a connecting rod or the like, and comprises a first half 9, and a second half 9z. The halves 9, and 92 have the same configuration and each includes: a backing 10; a lining layer 11 formed on an inner peripheral surface of the backing 10; and a surface layer 4 formed on a surface of the lining layer 11 and having a slide surface 4a in contact with a mating member 12. Optionally, a Cu deposit layer may be provided between the backing 10 and the lining layer 11, and an Ni deposit barrier layer may be provided between the lining layer 11 and the surface layer 4.

The backing 10 is formed from a rolled steel plate. The thickness of the backing 10 depends upon the thickness set for the slide bearing 9. The lining layer 11 is formed from copper, copper based alloy, aluminium, aluminium based alloy, etc.. The thickness of the lining layer 11 is in the range of 50 to 500m and normally of the order of 300 I'm. The surface layer 4 is formed from an aggregate of crystals of a Pb alloy. The thickness of the surface layer 4 is set in the range of 5 to 50 am and normally of the order of 20 I'm.

The Pb alloy forming the surface layer 4 contains 80 to 90 % by weight of Pb and 3 to 20 %byweightof Sn. If necessary, the Pb alloy may contain at most 10 % by weight of at least one element selected from the group consisting of Cu, In, Ag, Tl. Nb, Sb, Ni, Cd, Te, Bi, Mn, Ca and Ba.

Cu, Ni and Mn have the function of increasing the hardness of the surface layer 4. However, when the content of Cu, Ni and/or Mn exceeds 10 % by weight, the resulting surface layer has an excessively highdegreeofhardnesstwhichwillcause a reduced initial conformability.

When Cu or the like is added, it is desirable to control the Cu content such that the hardness Hmv of the resulting surface layer 4 is in the range of 15 to 25.

Each of In, Ag, Tl, Nb, Sb, Cd, Te, Bi, Ca and Ba hastefunction ofsoftening the surface layer 4 to improve an initial conformability.

However when the content of such elements exceeds 10 % by weight, the resulting surface layer 4 has a reduced strength. When In or the like is added, it is desirable to control the In content such that the hardness Hmv of the resulting surface layer 4 is in the range of 8 to 15.

The surface layer 4 is formed by an electroplating process, wherein a plating solution used is a borofluoride based plating solution containing 40 to 180 g/litre of Pb2+ , 1.5 to 35 g/litre of Sn2+ and optionally, at most 15 g/litre of Cu2+ together with an additive. The additive may may include at leastone organic additive selected form the group consisting of quinone based compoundssuch as hydroquinone, catechol, etc., amino acid based compounds such as gelatin, peptide, etc., and aldehyde such as benzaldehyde, vanillin. The added amount of the organic additives is set in the range of 1.5 to 18 g/litre in total. Optionally, boro fluoric acid and/or boric acid may be added to the plating solution to control the electrical resistance during energization. The temperature of the plating solution is set in the range of 5 to 35C.

and the cathode current density is set in the range of 3 to 15 A/dm2.

The surface layer 4 has first oriented crystals with a plane (hO0) of high atomic density directed towards the slide surface 4a so as to form the slide surface The The first oriented crystals have the functionofimproving the sliding characteristic of the surface layer 4.

The surface layer 4 may have, in addition to the first oriented crystals, second oriented crystals with planes (111) and (222) directed towards the slide surface.

In Pb alloy crystals. the plane (hOO) and the plane (111) including (222) have the relationship such that as one of the planes (hOO) and (111) increases, the other plane decreases.

Accordingly, except in a surface layer 4 comprising only the first oriented crystals, the first oriented crystals should be considered in correlation with the second oriented crystals.

In view of the above point, the abundance of the first oriented crystals in the surface layer 4 is preferably selected to comply with the following: In X-ray diffractometry of the surface layer 4, where the integrated intensity of the first oriented crystals with the plane (hOO) directed towards the slide surface 4a is represented by I(a), and the integrated intensity of the second oriented crystals with the plane (111) and (222) directed toward the slide surface 4a is represented by I(b), the following relation is established: 0.6 < I(a) / E I(ab) < 1.0 wherein E I(ab)= I(a) + I(b); I(b)= O is included ; and I(a) / E I (ab) represents the presence rate Ri,i.e,abundance, of the first oriented crystals.

As shown in Figs.25 and 26, the first oriented crystals 131 with the plane (hOO) directed towards the slide surface are columnar crystals extending from the lining layerllandhaving a quadrangular pyramid-shaped tip end 14 for forming the slide surface 4a.

If the presence rate R1 of the first oriented crystals 13, is set in the above-described manner, the apices 14a of the quadrangular pyramid-shaped tip ends 14 are caused to be preferentially worn so as to provide an improved initial conformability of the surface layer 4.

In addition, the surface area of the slide surface 4a can be enlarged by the quadrangular pyramid-shaped tip ends 14, so that the surface layer 4 has a sufficient oil retention property; This enhances the seizure resistance of the surface layer 4.

Because the first oriented crystal 13. has a face-centered cubic structure due to the orientation of the plane (h00), the atomic density increases in the direction of the orientation. This provides the surface layer 4withahighdegreeofhardnessandoilrentention property, thereby improving the wear resistance of the surface layer. In Figs.25 and 26, reference numeral 132 represents thesecondoriented crystals which are granular.

In order to provide the excellent sliding characteristics described above, the inclination of the first-oriented crystals 13, should be considered.

Referring to Fig.27, if a phantom plane C extending along the slide surface 4a is defined on the side of a base surface of the quadrangular pyramid-shaped tip end 14, and an inclination angle defined by a straight line e passing through the apex 14a of the quadrangular pyramid-shaped tip end 14 and a central portion 14b of the base surface and by a reference line f extending perpendicular to the phantom plane C through the central portion 14b is defined as 0, the inclination angle S of the first oriented crystals 13lispreferably in the range of 0 f S < 30 . When the inclination angle 8 becomes larger than 30 ( 6 > 30 ), the oil retention property of the surface layer 4 and the preferential wearing of the apices 14a are reduced thereby resulting in deterioration of the seizure resistance and the wear resistance of the surface layer 4.

Embodiment examples now will be described.

A lining layer 3 of a Cu alloy was subjected to an electroplating process to form a surface layer 4 comprising an aggregate of Pb alloy crystals.

The conditions for the electoplating process were as follows: the plating solution was a borofluoride plating solution containing 100 g/litre of Pb2+ , 10 g/litre of SnZ+ and 3 g/litre of Curt; an additive was an organic additive; the temperature of the plating solution was 25 C; and the current density was 8 A/dm2.

Fig.28 is a pattern diagram of an X-ray diffraction for the Pb crystals in the surface layer 4, wherein peak b4 indicates a plane (200), and peak bs indicates a plane (400). Both of the planes (200) and (400) belong to the plane (hOO). It is confirmed from fig.28 that the surface layer 4 comprises only the first oriented crystals 13i. In this case, the total integrated strength E I(ab) is equal to 679,996 (E I(ab)= 679,996), with the proviso that I(b)= O.

The value is equal to the integrated strength I(a) of the first oriented crystals 131. Therefore the presence rate R1 of the first oriented crystals 131 is equal to 1.0 (R, = 1.0).

Fig.29 is an electron photanicrograph (10,000 magnification ) showing the structure of a Pb alloy crystal in the slide surface 4a.

Fig.30 is an electron photanicro graph (5,000 magnification ) showingtestructure of a Pb alloy crystal at a longitudinal section of the surface layer 4. It can be seen from Figs.29 and 30 that the surface layer 4 comprises the first oriented crystals 13, namely the columnar crystals and the slide surface 4a is formed of quadrangular pyramid-shaped tip ends 14. The inclination angle 8 of the first oriented crystals 13, is in the range of O < 8 f 10 The Pb alloy contains 8% by weight of Sn and 2 % by weight of Cu.

Fig.31 is an electron photomicro graph (10,000 magnification ) showing the structure of a Pb alloy crystal in another slide surface 4a. Second oriented crystals 132 of the granular crystals are observed from Figs.31 in addition to the quadrangular pyramid-shaped tip ends 14.

In Fig.31, the integrated strength I(a) of the first oriented crystals 131 is equal to 37,172 ( I(a)= 37,172 ) and the integrated strength I(b) of the second oriented crystals 13z is equal to 24,781 ( I(b)= 24,781 ). Therefore the presence rate R, of the first oriented crystals 13l becomes 0.6 ( R1= 0.6 ). The inclination angle o of the first oriented crystals 13l is in the range of 0 # # # 10 .

Fig.32 illustrates the relationship between the presence rate R1 of the first oriented crystals 131 and the surface pressure when the seizure occurs for surface layers4 of various slide bearings 9. In Fig.

32, the line g1 represents the relationship in a case where the inclination angle 8 of the first oriented crystals 131 is in the range of 0 # # # 10 , the line g2 represents the relationship in a case where the inclination angle 8 of the first oriented crystals 131 is in the range of 0 # # # 20 , and the line g3 represents the relationship in a case where the inclination angle 8 of the first oriented crystals 13, is in the range of 0 # # # 30 .

The seizure test was carried out by bringing each of the slide bearings 9 into sliding contact with a rotary shaft and gradually increasing the load applied to the slide bearings 9.

The test conditions were as follows: the material of the rotary shaft was a nitrided JIS S48C material; the speed of rotation of the rotary shaft was 6,000 rpm; the oil supply temperature was 120C ; the oil supply pressure was 3 kg/cm2; and the applied load was 1 kg/sec.

As is apparent from Fig.32, the seizure resistance of the surface layer 4 can be improved by setting the pr~esencerate R, of the first oriented crystals 131 at a levei equal to or more than 0.6 (R11 2 0.6).

A preferable range of the presence rate R1 of the first oriented crystals 131 is 0.8 < R1 g 1.0. It should be noted that most excellent seizure resistance is obtained when R1= 1.0.

In the surface layer 4, third oriented crystals, namely Pb metal crystals with a crystal face other than planes (hOO), (111) and (222) directed towards the slide surface, may be precipitated in some cases.

These include planes (220), (311), (331) and (420). The third oriented crystals adversely affect the seizure resistance of the surface layer and hence, it is desirable to suppress the presence of the third oriented crystals.

In view of this problem, the presence rate of the third oriented crystals in the surface layer is preferably in accordance with the following: In X-ray diffractanetry of the surface layer 4, where the integrated intensity of the first oriented crystals with the plane (hOO) directed towards the slide surface 4a is represented by I(a), the integrated intensity of the second oriented crystals with the planes (111) and (222) directed towards the slide surface 4a is represented by I(b), and the integrated intensity of the third priented crystals with planes other than the planes (hOO), (111) and (222) directed towards the slide surface 4a is represented by I(c), the following relation is established: I(c)/ E l(abc) g 0.2 wherein # I(abc)= I(a) + I(b)+ 1(c); I(b) = 0 is included ; and I(c) / # I(abc) represents the presence rate R2 of the third oriented crystals.

Fig.33 illustrates the relationship between the presence rate Rz of the third oriented crystals and the surface pressure at the generation of seizure for the surface layers 4 of Various slide bearings 9. In Fig.33, the line h1 represents the relationship in a case where the presence rate R1 of the first oriented crystals 13, is equal to 1.0 (R1= 1.0) thus I(b)= 0 and the surface layer 4 comprises the first and third oriented crystals. The line hz represents the relationship in a case where the presence rate Rt of the first oriented crystals 131 is equal to 0.8 (R1 = 0.8) and the surface layer 4 comprises the first, second and third oriented crystals. The seizure test was carried out in the same manner and under the same conditions as those described above.

As is apparent from Fig.33, the seizure resistance can be improved by setting the presence rate R2 of the third oriented crystals at a level equal to or less than 0.2 (R2 5 0.2). The presence rate R2 of the third oriented crystals is preferably set in the range of R2 5 0.1. It is to be noted that P: 0 corresponds to the case where no third oriented crystals exist in the surface layer 4.

The optimum state of the surface layer 4 is achieved when the inclination angle 8 of the first oriented crystals 13, is in the range of 0. 5 6 5 10 and when the presence rate Rt of the first oriented crystals 13, is a value determined by the following expression: R,= I(a) / # I(abc) 2 0.8 It should be noted that the third embodiment of the present invention is also applicable to slide members other than the described slide bearing.

Claims

CLAIMS:

1. A slide member having a slide portion having a slide surface for engagement with a mating member, the slide portion having a surface layer comprising an aggregate of crystals of a lead alloy having crystal planes directed towards said slide surface whereby to form at least part of said surface, said aggregate comprising first oriented crystals having a (hOO) plane directed towards said slide surface and, optionally, second oriented crystals having (111) and (222) planes directed towards said surface, crystal surfaces being provided by (how) planes, the relative abundance of said first oriented crystals as determinable by X-ray diffractometry being at least 60W as expressed by the ratio I(a)/(1(a)+I(b)) where I(a) and I(b) are the integrated intensities for diffraction peaks correspondingly to the first and second oriented crystals respectively.

2. A slide member as claimed in claim 1 wherein said aggregate further comprises third oriented crystals having planes other than (hO0), (111) and (222) directed towards said surface, the relative abundance of said third oriented crystals as determinable by X-ray diffractometry being no more than 20W as expressed by the ratio I(c)/(I(a)+I(b)+I(c)) where I(a), I(b) and I(c) are the integrated intensities for diffraction peaks corresponding to the first, second and third oriented crystals respectively.

3. A slide member as claimed in claim 1 wherein the inclination angle o of an axis of the first oriented crystals relative to a line perpendicular to a plane of the slide surface is within the range of 0 < o < 300.

4. A slide member as claimed in claim 1 substantially as herein described in any one of the Examples and/or with reference to any one of the accompanying drawings.