Slide member and method of manufacturing the same

A slide member has a sliding surface made of ceramic and has a surface roughness of not more than 1.0 .mu.m in center line average roughness Ra. ceramic includes a silicon nitride sintered body, which contains crystal grains having a linear density of at least 35 per 30 .mu.m in length with a boundary phase volume ratio of not more than 15 volume %, and which contains pores of not more than 20 .mu.m in maximum diameter in a content of not more than 3%. In a method of manufacturing the slide member, it is possible to ensure smoothness of the sliding surface by grinding the sliding surface and thereafter heating the ceramic in either inert gas or an atmospheric air. A slide member that can be used under severe sliding conditions of high-speed sliding or the like and that has excellent wear resistance is obtained. Even if the slide member is used for a sliding part of a compressor or the like which employs a fluorocarbon containing no chlorine as a cooling medium, it is possible to prevent the occurrence of seizure and abnormal wear on the sliding surface.

FIELD OF THE INVENTION 
The present invention generally relates to a wear-resistant slide member 
and a method of manufacturing the same. More specifically, the invention 
relates to a slide member which can withstand severe sliding conditions of 
high-speed sliding or the like, and a slide member to be used in an 
atmosphere of a cooling medium, and a method of manufacturing the same. 
BACKGROUND INFORMATION 
Bearing members making sliding motions can be classified into those making 
a rolling motion and those making a sliding motion. A rolling bearing 
making the former rolling motion can be to a ball bearing, for example. 
This ball bearing generally in a complicated structure. Bearings making 
the latter sliding motion include contact type bearings (metal bush 
bearing and oil retaining bearing) and non-contact bearings (oil bearing, 
air bearing and magnetic bearing). These bearings have extremely simple 
structures as compared with the former rolling bearing. 
A slide bearing is widely used as a mechanical component, since its 
structure is simple. However, with increases in machine speed, problems of 
seizure and durability arise in a conventional slide bearing made of 
bearing steel. For this reason, ceramics have been carefully considered as 
a material for a slide member which is required to be wear-resistant under 
high-speed sliding. Furthermore, in office automation products or the 
like, it has become increasingly required to use oil-free bearings to 
reduce the requirement for cleaning. Also in this field, ceramics has been 
watched with interest as a material for a slide member. As to such 
ceramics, Al.sub.2 O.sub.3, ZrO.sub.2, SiC, Si.sub.3 N.sub.4 and the like 
are now being developed. In situations of oil-free high-speed sliding 
exceeding 1 m/sec., however, an impactive knock wear phenomenon is caused 
by contact between bearing members. In a conventional bearing body made of 
ceramics, therefore, it has been difficult to withstand such sliding. 
On the other hand, a slide bearing body is also incorporated in a sliding 
part of a compressor of a refrigerator, a freezer or a car air 
conditioner. In this case, the sliding part of the bearing body is placed 
in a cooling medium. A chlorofluorocarbon (CFC), which is one of the 
fluorocarbons, has been employed as the cooling medium. In particular, a 
typical cooling medium of such a chlorofluorocarbon is CFC12. Chlorine 
(Cl) is included in molecules of this CFC12. This chlorine prevents 
adhesion and reaction of the slide member on a sliding surface. Namely, 
the chlorine prevents seizure between sliding surfaces or the like as an 
extreme pressure additive. Therefore, the CFC12 containing this chlorine 
itself serves as an extremely effective lubricant. Under a fluorocarbon 
atmosphere of CFC12 or the like containing chlorine, therefore, the 
sliding part of the slide member rarely seizes or causes abnormal wear. In 
general, therefore, a metal member of cast iron or the like has been used 
as a sliding part of a compressor of a refrigerator or the like, which is 
used in an atmosphere of a cooling medium. Under a fluorocarbon atmosphere 
containing chlorine, as hereinabove described, neither seizure nor 
abnormal wear of the sliding part has been caused even if a metal member 
of cast iron or the like is used as the sliding part. 
In recent years, however, employment of chlorofluorocarbons, which are 
represented by CFC12, has been regulated to address the problem of 
destruction of the ozone layer in the stratosphere. This is because 
chlorine contained in the chlorofluorocarbons is one of the factors 
destroying the ozone layer. HFC134a containing no chlorine in its 
molecules, for example, is now expected to be used as a substitute for 
these chlorofluorocarbons. Thus, studies are now being conducted to 
investigate the use of fluorocarbons containing no chlorine as a cooling 
medium. In such a fluorocarbon containing no chlorine, however, no 
lubricating effect by chlorine can be expected. Thus, the problem arises 
that a metal such as cast iron used as a sliding part of a compressor or 
the like seizes to another metal or causes abnormal wear. 
OBJECTIVE OF THE INVENTION 
The present invention solves the aforementioned problems, and an object 
thereof is to provide a slide member having high wear resistance, which 
can withstand severe slide conditions represented by those of high-speed 
sliding, or a slide member which hardly causes seizure and abnormal wear 
even in an atmosphere of a fluorocarbon containing no chlorine, and a 
method of manufacturing the same. 
SUMMARY OF THE INVENTION 
In consideration of the aforementioned problems of the prior art, the 
inventors have made various studies and have made the present invention by 
finding that an excellent sliding property can be attained under severe 
slide conditions of high-speed rotation or the like by controlling a 
sliding surface of a slide member. 
Namely, a slide member according to one aspect of the present invention 
comprises a sliding surface which is made of ceramics and has a surface 
roughness of not more than 1.0 .mu.m in center line average roughness Ra. 
Preferably, the sliding surface has a surface roughness of not more than 
0.1 .mu.m in center line average roughness Ra. The center line average 
roughness Ra is defined under JISB0601 (ISO468). 
According to a preferred embodiment of the present invention, the ceramics 
is silicon ceramics, and more preferably, silicon ceramics including an 
Si.sub.3 N.sub.4 phase. Further, the ceramics includes a silicon nitride 
sintered body containing crystal grains in a linear density of at least 35 
per 30 .mu.m in length with a boundary phase volume ratio of not more than 
15 volume % and containing pores of not more than 20 .mu.m in maximum 
diameter in a content of not more than 3%. 
A sliding part structure according to another aspect of the present 
invention comprises a first slide member and a second slide member. The 
first slide member has one sliding surface. The second slide member has 
another sliding surface in contact with the one sliding surface. At least 
one of the sliding surfaces is made of ceramics, and has a surface 
roughness of not more than 1.0 .mu.m in center line average roughness Ra. 
According to still another aspect of the present invention a method of 
manufacturing a slide member having a sliding surface made of ceramics and 
having a surface roughness of not more than 1.0 .mu.m in center line 
average roughness Ra, comprises the following steps: 
(a) grinding the sliding surface; 
(b) heating the ceramics in either an inert gas or the atmospheric air 
after grinding the sliding surface. 
According to a preferred embodiment of the method of manufacturing a slide 
member according to the present invention, the step of heating the 
ceramics is carried out at a temperature of at least 800.degree. C. and 
not more than 1500.degree. C. 
A method of manufacturing a slide member according to a further aspect of 
the present invention comprises the following step, in addition to the 
aforementioned steps (a) and (b): 
(c) polishing the aforementioned sliding surface after heating the 
aforementioned ceramics. 
A slide bearing body is an example of the inventive slide member. 
A slide member according to a further aspect of the present invention 
comprises a sliding surface which is placed in an atmosphere of a cooling 
medium containing fluorine, and the sliding surface is made of ceramics 
and has a surface roughness of not more than 1.0 .mu.m in center line 
average roughness Ra. Preferably, the sliding surface is provided with a 
film mainly composed of carbon. The film mainly composed of carbon may 
have been previously formed before being applied to the slide member. 
Alternatively, the film may be formed during sliding. 
In the slide member according to the present invention, the center line 
average roughness Ra of the sliding surface is not more than 1.0 .mu.m. 
Thus, it is possible to reduce the wear rate and the driving torque at the 
same rotational frequency as compared with the conventional slide member. 
More preferably, the center line average roughness Ra is reduced to 0.1 
.mu.m or less to attain a further advantageous effect. 
The reasons for the above advantages can be explained as follows. When a 
surface of ceramics is subjected to machining such as grinding, surface 
imperfections such as surface roughening are formed. Such surface 
roughening may be a critical factor influencing the performance of a 
sliding material. When a fine irregularity of the surface is properly 
controlled and smoothed, then hardly any wearing powder results even if 
abrupt contacts of the sliding part or the like are caused by disturbances 
or the like. Namely, the wear rate is reduced. Thus, vibration that would 
be caused by the intervention of worn powder in the sliding surface is 
suppressed. Therefore, it is possible to reduce the torque necessary for 
driving the slide member at least by such suppression of the vibration. 
Consequently, the slide member according to the present invention is 
capable of withstanding high-speed sliding. Depending on the structure of 
the sliding part or sliding conditions, it is also possible to prepare 
only one of a pair of members forming a pair of sliding surfaces which are 
in contact with each other from the aforementioned ceramics. 
If the ceramics is silicon ceramics, a fine and dense surface layer of 
silica or the like is easily formed during sliding. Thus, an improvement 
in a sliding property such as a reduction of the coefficient of friction, 
for example, can be expected. 
Particularly when the ceramics includes an Si.sub.3 N.sub.4 phase, it is 
possible to obtain a sliding surface which is excellent in chipping 
resistance with no chipping resulting due to crystal grains falling out or 
the like in at least the surface of the ceramics forming the sliding 
surface. A slide member, in which at least a sliding surface is made of 
ceramics including an Si.sub.3 N.sub.4 phase, also has excellent wear 
resistance against high-speed sliding accompanied by a knock wear 
phenomenon. Therefore, it is possible to suppress an increase of the 
required driving torque when correspondingly increasing the sliding speed. 
When the sliding surface is formed of a sintered body including an Si.sub.3 
N.sub.4 phase, the silicon nitride sintered body contains crystal grains 
in a linear density of at least 35 per 30 .mu.m in length with a boundary 
phase volume ratio of not more than 15 volume %, preferably not more than 
10 volume %. Further, the silicon nitride sintered body contains pores of 
not more than 20 .mu.m, preferably not more than 10 .mu.m in maximum 
diameter, while the content of the pores is controlled at 3% or less. 
Therefore, the surface of the silicon nitride sintered body forming the 
sliding surface is not chipped by crystal grains falling out or the like, 
so is also excellent in chipping resistance. Thus, the slide member of a 
silicon nitride sintered body according to the present invention also has 
excellent wear resistance against high-speed sliding accompanied by a 
knock wear phenomenon. 
In the method of manufacturing the slide member according to the present 
invention, it is preferable to perform heat treatment on the ceramics in 
an inert atmosphere or the atmospheric air after grinding the sliding 
surface. The reason for this will now be described. 
In addition to surface toughening, fine microcracks of micron or submicron 
order and residual stress are introduced into the ground ceramics. These 
can also serve as critical factors influencing the performance of the 
slide member. When the ceramics is heated under an inert atmosphere or in 
the atmospheric air, reaction products are formed in the ceramics. The 
reaction products are SiO.sub.x (x: arbitrary positive integer) in Si 
ceramics, for example. Due to this heat treatment, further, atomic 
migration takes place in the ceramics through diffusion. Therefore, the 
microcracks are recombined and the defect is remedied by the above 
described formation of the reaction products or atomic migration, or a 
synergistic effect of these. In addition, this heat treatment also has an 
effect of removing residual stress. 
Thus, it is possible to remove microcracks and residual stress from the 
ceramics by performing the heat treatment. Therefore, wear powder (i.e. 
powder produced by wear) is hardly caused by abrupt contact of a sliding 
part resulting from disturbance or the like. Thus, it is possible to 
suppress increase of the required driving torque corresponding to an 
increase of the sliding speed. 
The ceramics is preferably heated at a temperature of at least 800.degree. 
C. and not more than 1500.degree. C. It is possible to further facilitate 
formation of reaction products and atomic migration in the ceramics by 
heating the same at a temperature of at least 800.degree. C. If the 
heating temperature exceeds 1500.degree. C., on the other hand, the 
ceramics is unpreferably resintered to cause regrowth of the crystal 
grains. 
When the sliding surface is polished after the ceramics is subjected to 
heat treatment, fragile reaction products formed on the surface are 
removed with the effect being the smoothing of the reaction products, 
whereby a slide member comprising a more stable sliding surface having 
disturbance resistance can be obtained. 
When the inventive slide member is used for to a slide bearing body, the 
driving torque is so reduced that a high-speed sliding motion is enabled 
with a small driving torque. 
Further, the inventors have found that it is extremely effective to 
introduce ceramics into a slide member which is used in an atmosphere of a 
cooling medium containing fluorine, in order to prevent seizure and 
abnormal wear. 
The reason why seizure and abnormal wear can be prevented can be explained 
as follows. Ceramics is superior in Young's modulus and inferior in 
chemical reactivity as compared with a metal material such as cast iron. 
Since the ceramics has a lower chemical reactivity, a reaction such as 
chemical adhesion is hardly caused on a sliding surface of a slide member 
containing ceramics. Thus, it is possible to prevent seizure and abnormal 
wear resulting from chemical adhesion or the like in a slide member 
containing ceramics. Therefore, the slide member containing ceramics also 
operates normally when the same is used in an atmosphere of a cooling 
medium containing fluorine, such as a fluorocarbon containing no chlorine. 
The atmosphere of a cooling medium containing fluorine in the present 
invention may be a fluorocarbon in at least either a gas or a liquid form. 
Further, the cooling medium in the present invention may be at least 
either a hydrofluorocarbon (HFC) or a hydrochlorofluorocarbon (HCFC). 
Molecular formulas of typical hydrofluorocarbons are shown in Table 1. 
TABLE 1 
______________________________________ 
Code Molecular Formula 
______________________________________ 
HFC 32 CH.sub.2 F.sub.2 
HFC 125 CHF.sub.2 --CF.sub.3 
HFC 134 CHF.sub.2 --CHF.sub.2 
HFC 134a CH.sub.2 F--CF.sub.3 
HFC 143a CH.sub.3 --CF.sub.3 
HFC 152a CH.sub.3 --CHF.sub.2 
HFC 227 CF.sub.3 --CHF--CF.sub.3 
______________________________________ 
The slide member according to the present invention is also effective under 
an atmosphere of a hydrofluorocarbon other than those shown in Table 1. 
Further, molecular formulas of typical hydrochlorofluorocarbons are shown 
in Table 2. 
TABLE 2 
______________________________________ 
Code Molecular Formula 
______________________________________ 
HCFC 22 CHClF.sub.2 
HCFC 123 CHCl.sub.2 --CF.sub.3 
HCFC 124 CHCl.sub.F --CF.sub.3 
HCFC 141b CH.sub.3 --CCl.sub.2 F 
HCFC 142b CH.sub.3 --CClF.sub.2 
HCFC 225ca CF.sub.3 --CF.sub.2 --CHCl.sub.2 
HCFC 225cb CF.sub.2 Cl--CF.sub.2 --CHClF 
______________________________________ 
The ceramics forming the sliding surface according to the present invention 
is preferably at least one selected from a group of oxides, carbides, 
nitrides, borides and silicides. Tables 3 and 4 show typical monolithic 
ceramics and composite materials employing those ceramics. 
TABLE 3 
______________________________________ 
Monolithic Ceramics 
______________________________________ 
Oxide Alumina, Mullite, Spinel, Zirconia 
Carbide 
Silicon Carbide, Titanium Carbide 
Nitride 
Silicon Nitride, Aluminum Nitride, Titanium Nitride 
Boride Boron Nitride, Boron Carbide 
Silicide 
Titanium Silicide 
______________________________________ 
TABLE 4 
______________________________________ 
Composite Material 
______________________________________ 
Long Fiber Reinforced 
Carbon Fiber Reinforced Silicon 
Composite Material 
Nitride, 
Silicon Carbide Fiber Reinforced 
Silicon Nitride, 
Alumina Fiber Reinforced Glass 
Whisker Reinforced 
Silicon Carbide Whisker Reinforced 
Composite Material 
Alumina, 
Silicon Carbide Whisker Reinforced 
Silicon Nitride 
Particle Dispersion- 
Titanium Nitride Particle Dispersion- 
Strengthened Strengthened Silicon Nitride, 
Composite Material 
Silicon Carbide Nanoparticle 
Dispersion-Strengthened Alumina, 
Silicon Carbide Nanoparticle 
Dispersion-Strengthened Silicon 
Nitride 
______________________________________ 
It is possible to use ceramics other than those shown in Tables 3 and 4 or 
a composite material employing such ceramics as the ceramics forming the 
sliding surface according to the present invention. 
It is preferable that the slide member consists of a pair of members 
forming a pair of sliding surfaces which are in contact with each other, 
and at least one of the members is made of ceramics. In this case, one of 
the members forming the sliding surfaces must be made of ceramics, while 
the other member may be made of a metal, or may be prepared from a 
material such as the same or different types of ceramics, a carbon 
material, or a resin such as Teflon. 
The inventors have found that there is a relation between surface 
roughness, seizure resistance and wear of a sliding surface of a slide 
member which, is used in an atmosphere of a cooling medium containing 
fluorine. According to this, surface roughness of the sliding surface of 
the inventive slide member is preferably not more than 1.0 .mu.m Ra. If 
the surface roughness of the sliding surface exceeds 1.0 .mu.m Ra, one 
ceramics member may damage another metal member, or one and another 
ceramics members may cause abnormal wear, depending on the surface 
pressure of the sliding surface. When the surface roughness of the sliding 
surface is not more than 1.0 .mu.m Ra, on the other hand, one ceramics 
member hardly damages another member or hardly causes abnormal wear with 
another member. The reason for this can be explained as follows. 
When the surface roughness of the sliding surface of the slide member is 
made not more than 1.0 .mu.m Ra, the irregularity on the sliding surface 
is reduced. Namely, the surface is smoothed. Thus, wear is hardly caused 
by abrupt contact of the sliding part resulting from disturbance or the 
like. Consequently, it is possible to suppress a mechanical frictional 
phenomenon by making the sliding surface not more than 1.0 .mu.m Ra. 
The inventors have also found that it is possible to attain a further 
effect by further smoothing the surface roughness of the sliding surface 
of the inventive slide member to be not more than 0.1 .mu.m Ra. It has 
been recognized that an excellent low coefficient of friction is obtained 
particularly in an atmosphere of a cooling medium containing fluorine, to 
attain excellent wear resistance. This is conceivably because the 
irregularity of the sliding surface can be further reduced by making the 
surface roughness not more than 0.1 .mu.m Ra. Thus, it is possible to 
further suppress a mechanical frictional phenomenon even in an atmosphere 
of a cooling medium containing fluorine. 
Further, the inventors have found that the sliding surface exhibits a low 
coefficient of friction and high wear resistance when a film which is 
mainly composed of carbon is formed on the sliding surface of the slide 
member. This is because friction and wear are reduced by a solid 
lubricating action of the carbon. Thus, it is possible to further reduce a 
mechanical frictional phenomenon even in an atmosphere of a cooling medium 
containing fluorine by forming a film which is mainly composed of carbon 
on the sliding surface. 
The inventors have found that there is a relation between surface roughness 
and wear resistance of a slide member including a film mainly composed of 
carbon on its sliding surface. Accordingly, the surface roughness of the 
inventive slide member having the film mainly composed of carbon is 
preferably not more than 1.0 .mu.m Ra. This is because one member may 
damage a film, mainly composed of carbon, which is formed on a surface of 
another member, or cause abnormal wear thereon depending on the surface 
pressure of the sliding surface if the surface roughness of the sliding 
surface exceeds 1.0 .mu.m Ra. As a result, the solid lubricating action of 
the film may not be sufficiently attained. 
Further, the inventors have found that it is possible to attain a low 
coefficient of friction and excellent wear resistance in an atmosphere of 
a cooling medium containing fluorine by making the surface roughness of 
the inventive slide member provided with a film, which is mainly composed 
of carbon, not more than 0.1 .mu.m Ra. This is conceivably because it is 
possible to further reduce the irregularity of the sliding surface by 
making the surface roughness not more than 0.1 .mu.m Ra. As a result, it 
is thereby possible to further reduce a mechanical frictional phenomenon 
even in an atmosphere of a cooling medium containing fluorine as the 
result. 
The inventors have found a method of forming a film mainly composed of 
carbon on the sliding surface during sliding, by employing a material such 
as cast iron containing free carbon for one of the inventive sliding 
members. According to this method, the free carbon falls from the 
respective sliding member during an initial stage of sliding, to form a 
carbon film on the sliding surface of the other slide member. When the 
surface roughness of the sliding surface exceeds 1.0 .mu.m Ra, the rate of 
wear exceeds the rate of formation of the film mainly composed of carbon, 
whereby of no film is formed. When the surface roughness of the sliding 
surface is not more than 1.0 .mu.m Ra, on the other hand, a film mainly 
composed of carbon is formed because hardly any wear is caused. 
Accordingly, it is possible to suppress a mechanical frictional phenomenon 
without coating the sliding surface with a material having solid lubricity 
such as carbon or molybdenum disulfide in advance of employment of the 
slide member. 
Further, the inventors have found that it is possible to form a film mainly 
composed of carbon on the sliding surface during sliding in a cooling 
medium containing fluorine by making the surface roughness of the sliding 
surface not more than 0.5 .mu.m Ra, thereby obtaining a sliding surface 
which has a lower coefficient of friction, and which is particularly 
excellent in wear resistance. This is based on the fact that it is 
possible to further reduce the irregularity of the sliding surface by 
making the surface roughness not more than 0.5 .mu.m Ra for enabling 
stable formation of a film mainly composed of carbon on the surface, 
whereby a solid lubricating action of the carbon is properly attained as 
the result. Thus, it is possible to further suppress a mechanical 
frictional phenomenon even in an atmosphere of a cooling medium containing 
fluorine. 
More preferably, the aforementioned effect can be further remarkably 
implemented by making the surface roughness of the sliding surface not 
more than 0.1 .mu.m Ra. 
According to the present invention, as hereinabove described, a slide 
member is provided, which has excellent wear resistance, and which can be 
used under severe sliding conditions of high-speed sliding or the like. 
Particularly in the slide member according to the present invention, it is 
possible to reduce surface toughening on the sliding surface by 
controlling the center line average roughness Ra of the sliding surface to 
not more than 1.0 .mu.m. Thus, wear powder is hardly caused by abrupt 
contact of a sliding part resulting from disturbance or the like. 
Therefore, it is possible to suppress an increase of the required driving 
torque corresponding to an increase of a vibration frequency which is 
caused by wear powder. Consequently, the inventive slide member can 
withstand high-speed sliding. 
Further, it is possible to prevent seizure and abnormal wear even when the 
inventive slide member is used in an atmosphere of a cooling medium 
containing fluorine.

DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE BEST MODE 
OF THE INVENTION 
Example 1 
The inventors have made the following experiment on Si.sub.3 N.sub.4 
ceramics, which is excellent in toughness among ceramics materials. 
First, raw material powder of Si.sub.3 N.sub.4 having a mean particle 
diameter of 0.3 .mu.m, particle size distribution 3.sigma.=0.2 .mu.m, an 
.alpha. crystallization rate of 96.5% and an oxygen content of 1.4 weight 
% was prepared. 92 weight % of this raw material powder of Si.sub.3 
N.sub.4 was mixed with 4 weight % of Y.sub.2 O.sub.3 powder having a mean 
particle diameter of 0.8 .mu.m, 3 weight % of Al.sub.2 O.sub.3 powder 
having a mean particle diameter of 0.5 .mu.m, and 1 weight % of AlN powder 
having a mean particle diameter of 1.0 .mu.m. Utilizing a ball mill, these 
powder materials were wet-blended in ethanol for 100 hours. Thereafter the 
mixed powder was dried and then subjected to CIP (cold isostatic pressing) 
treatment under a pressure of 5000 kg/cm.sup.2. The as-obtained compact 
was heated and held in a gaseous nitrogen atmosphere of 1 atm. at 
1600.degree. C. for 4 hours. Further, sintering treatment was performed on 
this compact at a temperature of 1750.degree. C. for 6 hours, thereby 
obtaining a sintered body. Thereafter this sintered body was subjected to 
HIP (hot isostatic pressing) treatment at a temperature of 1700.degree. C. 
under a pressure of 1000 atm. in a gaseous nitrogen atmosphere for 2 
hours. 
The as-obtained Si.sub.3 N.sub.4 sintered body contained crystal grains in 
a linear density of at least 35 per 30 .mu.m in length and contained pores 
of not more than 20 .mu.m with maximum diameter in a boundary phase volume 
ratio of not more than 15 volume %, and with porosity of not more than 3%. 
Further, this Si.sub.3 N.sub.4 sintered body had a mean major axis 
particle diameter of not more than 5 .mu.m, an aspect ratio of at least 4, 
and a maximum major axis particle diameter of not more than 15 .mu.m. In 
addition, this sintered body had JIS three-point bending strength of at 
least 80 kg/mm.sup.2, and a fracture toughness value of at least 5 
MPa.multidot.m.sup. 1/2. 
Sintered bodies having such characteristics were subjected to cylindrical 
grinding by a cylindrical grinder. Conditions employed for the grinding 
were a peripheral speed of 1400 m/min. and a feed rate of 260 m/min. 
Further, the grindstones of the cylindrical grinder were successively 
exchanged from that of 200 meshes/in. to that of 800 meshes/in., thereby 
finishing surfaces of the sintered bodies to desired surface roughness 
levels. The obtained samples Nos. 1 to 4 are shown in the following Table 
5. 
After the above this cylindrical grinding was performed, the sintered 
bodies were subjected to heat treatment in a heating furnace at a 
temperature of 1000.degree. C. for 1 hour. Thereafter the sintered bodies 
were polished by a buffing machine under conditions of a peripheral speed 
of 1400 m/min. and a feed rate of 260 m/min., using a diamond lapping 
solution of 1500 meshes/in. in grain size as a polishing solution. The 
obtained samples Nos. 5 to 8 are shown in the following Table 5. 
TABLE 5 
______________________________________ 
Finished Surface 
Roughness Heat Treatment 
No. Curve Ra (.mu.m) 1000.degree. C. .times. 1 hr. 
Mark 
______________________________________ 
1 a 2.0 .mu.m No .DELTA. 
2 b 1.0 No .quadrature. 
3 c 0.5 No .largecircle. 
4 d 0.1 No .diamond. 
5 e 2.0 Yes .tangle-solidup. 
6 f 1.0 Yes .box-solid. 
7 g 0.5 Yes .circle-solid. 
8 h 0.1 Yes .diamond-solid. 
______________________________________ 
The samples Nos. 1 to 8 shown in Table 5 obtained in the aforementioned 
manner were subjected to wear resistance evaluation by an Amsler abrasion 
test. The Amsler abrasion test is a test employing two ring-type test 
samples (outer diameter of .phi.16 mm by inner diameter of .phi.30 mm by 
thickness of 8 mm) and making a sliding test with a prescribed load P and 
a rotational speed V and thereafter measuring weight reduction values of 
the samples, thereby evaluating wear resistance. 
FIG. 1 is a graph showing the results of the experiment involving an Amsler 
abrasion test on the respective samples shown in Table 5. Referring to 
FIG. 1, the axis of abscissas shows products (P.multidot.V values) of 
loads P and rotational speeds V. Further, the axis of ordinates shows wear 
rates. Marks such as .largecircle. and .circle-solid. appearing in the 
figure correspond to the respective samples shown in Table 5. For the 
purpose of comparison, FIG. 1 also shows the results of 5Y5A and 5Y5L 
materials, which are Si.sub.3 N.sub.4 sintered bodies indicated in Yogyo 
Kyokai-Shi, Vol. 93, 1985, p. 73, in solid and two-dot chain lines 
respectively. As can be seen from this figure, wear resistance is improved 
as surface roughness Ra is reduced. Further, it is understood that wear 
resistance of the sintered body is further improved when heat treatment is 
performed at a temperature of 1000.degree. C. for 1 hour. In addition, it 
is understood that an effect of improving wear resistance is remarkable 
when surface roughness is not more than 1.0 .mu.m in Ra. 
As hereinabove described, it has been proved that an Si.sub.3 N.sub.4 
sintered body having finished surface roughness Ra of not more than 1.0 
.mu.m is extremely excellent in wear resistance. Further, it has also been 
proved that the wear resistance is further improved by performing heat 
treatment on this Si.sub.3 N.sub.4 sintered body. 
It has also been confirmed that improved wear resistance can also be 
similarly attained when the aforementioned treatment is performed on Al or 
Zr ceramics, under conditions that do not change the original mechanical 
properties (bending strength, for example) of the material. Therefore, the 
aforementioned treatment for controlling surface roughness is applicable 
to all ceramics. 
Then, the performance attained when using the inventive slide member as a 
bearing body was examined. 
First, Si.sub.3 N.sub.4 sintered bodies obtained in the aforementioned 
method were employed as the materials for bearing bodies. As hereinabove 
described, the sintered bodies which were subjected to HIP treatment were 
surface-ground by a surface grinder. Conditions employed for this grinding 
were a peripheral speed of 1800 m/min. and a feed rate of 260 m/min. 
Further, grindstones of the surface grinder were successively exchanged 
from that of 200 meshes/in. to that of 800 meshes/in., thereby finishing 
the surfaces of the sintered bodies to desired surface roughness levels. 
Thus, respective samples were prepared. Some of the samples were subjected 
to heat treatment in a heating furnace at a temperature of 1000.degree. C. 
for 1 hour after the surface grinding. Further, other ones of the samples 
were subjected to buffing as a method of polishing. A diamond lapping 
solution of 1500 meshes/in. in grain size was employed as a polishing 
solution under conditions of a peripheral speed of 1800 r.p.m. and a feed 
rate of 260 m/min., to polish the samples using a buffing machine. Thus, 
the samples shown in the following Table 6 were obtained. 
TABLE 6 
__________________________________________________________________________ 
Surface Treatment 
Roughness 
Heat Treatment 
after 
(Ra) Condition Grinding 
Mark 
Remarks 
__________________________________________________________________________ 
A0 2.0 .mu.m 
-- -- .box-solid. 
Conventional 
Material 
A1 2.0 .mu.m 
1000.degree. C. for 1 Hour 
Polish 
.quadrature. 
Comparative 
in Atmospheric Air Material 
B0' 
1.0 .mu.m 
-- -- .tangle-soliddn. 
Developed 
Material 
B1' 
1.0 .mu.m 
1000.degree. C. for 1 Hour 
-- .gradient. 
Developed 
in Atmospheric Air Material 
B0 1.0 .mu.m 
-- Polish 
.tangle-solidup. 
Developed 
Material 
B1 1.0 .mu.m 
1000.degree. C. for 1 Hour 
Polish 
.DELTA. 
Developed 
in Atmospheric Air Material 
C0 0.5 .mu.m 
-- -- .circle-solid. 
Developed 
Material 
C1 0.5 .mu.m 
1000.degree. C. for 1 Hour 
Polish 
.largecircle. 
Developed 
in Atmospheric Air Material 
D0 0.08 .mu.m 
-- -- .diamond-solid. 
Developed 
Material 
D1 0.08 .mu.m 
1000.degree. C. for 1 Hour 
-- .diamond. 
Developed 
in Nitrogen Material 
__________________________________________________________________________ 
The aforementioned samples shown in Table 6 were employed to form bearing 
bodies. 
FIG. 2 is a schematic diagram showing the structure of a composite bearing 
body used for testing the performance of a bearing body. Referring to FIG. 
2, the composite bearing body 10 is formed by an inner ring 1, an outer 
ring 2 and thrust plates 3 and 4. The inner ring 1 has a cylindrical 
shape, to enclose an outer peripheral surface of a prescribed shaft. The 
thrust plates 3 and 4 are set to be in contact with both end surfaces of 
the inner ring 1. The outer ring 2 is adjusted to maintain prescribed 
clearances with respect to the inner ring 1 and the thrust plates 3 and 4. 
Further, the clearances are adjusted to fine values, in order to maintain 
radial rotation accuracy during high-speed rotation. 
FIG. 3 is a schematic diagram showing the structure of an evaluation tester 
for evaluating the performance of the aforementioned composite bearing 
body. The composite bearing body is formed by an inner ring 11, an outer 
ring 12 and thrust plates 13 and 14. A respective composite bearing body 
is formed from each sample of the Si.sub.3 N.sub.4 ceramics sintered body 
shown in Table 6. The outer ring 12 is so provided as to maintain a 
prescribed clearance with respect to the inner ring 11. Further, this 
outer ring 12 also maintains prescribed clearances with respect to the 
thrust plates 13 and 14. The inner ring 11 to which the thrust plates 13 
and 14 are bonded is provided with a hole having an inner diameter of 10 
mm from its cylindrical upper surface to its cylindrical lower surface. A 
rotator 15 is fitted in this hole. The inner ring 11 is rotatable with 
this rotator 15. The rotator 15 is set to be rotatable by a motor 16. 
Driving torque of this motor 16 is measured by a torque meter 17. 
The bearing performance evaluation tester is constructed in the 
aforementioned manner. This bearing performance evaluation tester was 
employed for making the rotational frequency of the rotator 15 reach a set 
value, thereafter maintaining the rotational frequency for 10 minutes, and 
then measuring the driving torque at that time using the torque meter 17. 
FIG. 4 is a graph showing the results of the driving torque of rotators 
measured using composite bearing bodies which were formed by the 
respective samples of Table 6. Referring to FIG. 4, marks such as 
.largecircle. and .circle-solid. appearing in the figure correspond to the 
respective samples of Table 6. The axis of abscissas shows rotational 
frequencies (r.p.m.) of the rotators supported by the respective composite 
bearing bodies (or, peripheral speeds (m/sec.) in inner peripheral 
surfaces of the inner rings). The axis of ordinates shows driving torque 
values (g.multidot.cm). As can be seen from this figure, it is understood 
that the ratio of an increase rate of the driving torque to that of the 
rotational frequency (peripheral speed) is reduced as the surface 
roughness Ra after grinding is reduced. It is also understood that the 
ratio of the increase rate of the driving torque to that of the rotational 
frequency is reduced by performing heat treatment, and also further 
reduced in the samples subjected to buffing as a method of polishing. In 
the samples A0 and A1, seizure occurred in sliding parts when the 
rotational frequencies exceeded 15000 r.p.m. 
From the aforementioned results, it is understood that the increase of 
driving torque related to an increase of the rotational speed can be 
extremely suppressed in each sample having surface roughness Ra of not 
more than 1.0 .mu.m. 
As representative practical examples of the inventive slide member can be 
used for a bearing for an office automation product which is required to 
rotate at a high speed, a turbine bearing for a supercharger which rotates 
at a high speed of 80000 to 150000 r.p.m., a bearing for a turbine or a 
compressor which rotates at a high speed of 20000 to 30000 r.p.m., a 
bearing for high-speed rotation which is employed for a rocket engine 
turbo-pump, a bearing which is employed for a machine tool such as a CNC 
ultraprecise lathe, an ultraprecise lathe for cylindrical working or an 
ultraprecise surface grinder, and the like. 
Example 2 
A method of manufacturing a silicon nitride sintered body as a material for 
a slide member according to an example of the present invention will now 
be described. 
Raw material powder of Si.sub.3 N.sub.4 having a mean particle diameter of 
0.3 .mu.m, grain size distribution of 3.sigma.=0.20 .mu.m, an .alpha. 
crystallization rate of 96.5% and an oxygen content of 1.4 weight % was 
prepared. 92 weight % of this Si.sub.3 N.sub.4 raw material powder, 4 
weight % of Y.sub.2 O.sub.3 powder having a mean particle diameter of 0.8 
.mu.m, 3 weight % of Al.sub.2 O.sub.3 powder having a mean particle 
diameter of 0.5 .mu.m and 1 weight % of MgO powder having a mean particle 
diameter of 1.0 .mu.m were wet-blended in ethanol for 100 hours using a 
ball mill. Thereafter a mixed powder obtained by drying the above 
wet-blended substance was subjected to CIP (cold isostatic press) molding 
under a pressure of 5000 kg/cm.sup.2. The as-obtained compact was heated 
and held under a gaseous nitrogen atmosphere of 1 atm. at a temperature of 
1600.degree. C. for 4 hours. Further, sintering treatment was performed at 
a temperature of 1750.degree. C. for 6 hours, to obtain a sintered body. 
Thereafter HIP (hot isostatic press) treatment of 2 hours was performed on 
this sintered body at a temperature of 1700.degree. C. in a gaseous 
nitrogen atmosphere of 1000 atm. 
In the silicon nitride sintered body obtained in the aforementioned manner, 
the mean major axis particle diameter was not more than 5 .mu.m, the 
aspect ratio of crystal grains thereof was at least 4, and the maximum 
major axis particle diameter was not more than 15 .mu.m. This sintered 
body had mechanical properties of JIS three-point bending strength of at 
least 80 kg/mm.sup.2 and a fracture toughness value of at least 5 
MPa.multidot.m.sup. 1/2. Test pieces were cut from the as-obtained 
sintered body, to evaluate wear resistance levels in accordance with an 
Amsler abrasion test. 
FIG. 5A is a graph showing relations between products (P.multidot.V) of 
loads (P) applied to the samples and rotational speeds (V), and the 
resultant wear rates. Referring to FIG. 5A, respective curves a to e 
show results of measurement obtained by the following samples: 
a: Inventive Sample 
A silicon nitride sintered body obtained by the aforementioned 
manufacturing method, having a crystal grain linear density of 40 per 30 
.mu.m in length, a boundary phase volume ratio of 8 volume %, porosity of 
0.05%, a and a maximum pore diameter of 8 .mu.m. 
b: Comparative Sample 
A silicon nitride sintered body obtained by the aforementioned 
manufacturing method, having a crystal grain linear density of 30 per 30 
.mu.m in length, a boundary phase volume ratio of 16 volume %, porosity of 
3.2%, a and a maximum pore diameter of 22 .mu.m. 
c, d and e: Conventional Samples 
Samples of silicon nitride sintered bodies shown in Yogyo Kyokai-shi, Vol. 
93, 1985, pp. 73 to 80 (FIG. 3, in particular). 
The Amsler abrasion test was conducted by fixing two ring-shaped samples 
(inner diameter of .phi.16 mm by outer diameter of .phi.30 mm by thickness 
of 8 mm) to a rotary shaft of a tester in such an arrangement that 
respective circumferential surfaces were correctly in contact with each 
other, applying a prescribed load and driving the rotary shaft at a 
prescribed rotational frequency to carry out a sliding test of about 
100,000 revolutions, and thereafter measuring the respective degrees or 
amounts of weight reduction of the two samples. 
As clearly understood from FIG. 5A, the sintered body according to the 
present invention is extremely excellent in wear resistance. FIG. 5B shows 
the value of P.multidot.V (kg.multidot.m/s) in FIG. 5A converted or 
normalized per unit area of sliding surface. 
Example 3 
An Amsler abrasion test was carried out in liquid HFC134a, using sintered 
bodies of the inventive sample a and the comparative sample b obtained 
in Example 2. At this time, the abrasion test was carried out under the 
same load and rotational frequency conditions as Example 2, in such a 
manner that contact portions of two ring-shaped samples (outer diameter of 
16 mm by inner diameter of 30 mm by thickness of 8 mm) were dipped in the 
liquid HFC134a. 
FIG. 6 is a graph showing relations between products (P.multidot.V) of the 
loads (surface pressures (P)) applied to the samples and the rotational 
speeds (V), and the resultant wear rates. As can be seen from FIG. 6, it 
is understood that the sintered body according to the present invention is 
also extremely excellent in wear resistance in an environment of a 
substitutional fluorocarbon. 
Example 4 
Rings were respectively prepared from sintered bodies of the inventive 
sample a and the comparative sample b obtained in Example 2, bearing 
steel and high-speed steel. Rings having sliding surfaces whose surface 
roughness levels were adjusted to 0.01, 0.1, 0.5 and 3 .mu.m Ra 
respectively were prepared from each material. Rings of spheroidal 
graphite cast iron were prepared as counter materials for sliding with 
respect to these rings. The respective rings having various surface 
roughness levels of the sliding surfaces and the rings of spheroidal 
graphite cast iron were arranged to slide in a three-type mixture 
substitutional fluorocarbon solution of HCFC22/HFC152a/HCFC124. At this 
time, seizure loads were measured using a ring-on-ring friction tester 
while varying the loads, with a peripheral speed of 2 m/sec. Each seizure 
load was determined at a point of time when an echo was generated during 
the test and vibration of the tester took place. The results are shown in 
Table 7. 
TABLE 7 
______________________________________ 
Seizure Load (kg/cm.sup.2) 
3 0.5 0.1 0.01 
Sliding Surface Roughness 
.mu.mRa .mu.mRa .mu.mRa 
.mu.mRa 
______________________________________ 
Sample 
Sintered Body of 
49 103 152 185 
Inventive Sample a 
Sintered Body of 
23 47 72 86 
Comparative 
Sample b 
Bearing Steel 2 5 8 12 
High-Speed Steel 
2 6 9 14 
______________________________________ 
As can be seen from Table 7, it has been proved that a high seizure load 
can be attained by using a slide member formed by the sintered body of the 
inventive sample a, and an especially higher seizure load can be attained 
when surface roughness is reduced to not more than 1.0 .mu.m Ra, and 
further reduced to not more than 0.1 .mu.m Ra. 
Example 5 
Shoes to be in contact with swash plates made of an Al-Si alloy in swash 
plate compressors for car air conditioners were formed by sintered bodies 
of the inventive sample a and the comparative sample b obtained in 
Example 2. These shoes were employed for evaluating peripheral speeds at 
which seizure between the shoes and the swash plates occurred while using 
HFC134a as a cooling medium and polyalkylene glycol as a lubricant. 
Surface roughness levels of the sliding surfaces of the shoes were set at 
0.1 .mu.m RA. Occurrence of seizure was determined by generation of an 
abnormal noise and an abnormal increase of a driving current value. The 
results are shown in Table 8. 
TABLE 8 
______________________________________ 
Sample Seizure Peripheral Speed (m/sec.) 
______________________________________ 
Sintered Body of 
18 
Inventive Sample a 
Sintered Body of 
8 
Comparative Sample b 
______________________________________ 
As can be seen from Table 8, it has been proved that seizure occurs at a 
high peripheral speed when a shoe made of the sintered body according to 
the inventive sample is employed. 
Although a sliding component for a compressor has been evaluated and 
described as an example of the inventive slide member, the present 
invention is not restricted thereto. The slide member according to the 
present invention can also be used for a turbine bearing for a 
supercharger which rotates at a high speed of 80000 to 150000 r.p.m., a 
bearing employed for a turbine which rotates at a high speed of 20000 to 
30000 r.p.m., a machine tool such as a CNC ultraprecise lathe, an 
ultraprecise lathe for cylindrical working or an ultraprecise surface 
grinder, or the like. 
Example 6 
Rings of spheroidal graphite cast iron were prepared as first members 
forming sliding surfaces. Further, rings were respectively prepared from 
spheroidal graphite cast iron, bearing steel, alumina, silicon carbide, 
silicon nitride, boron nitride, carbon fiber reinforced silicon nitride, 
silicon carbide whisker reinforced alumina, and silicon carbide 
nanoparticle dispersion-strengthened alumina as second members forming the 
sliding surfaces. The first and second rings were arranged and driven to 
slide for measuring seizure loads while varying the applied loads in a 
liquid of HFC134a with a condition of a peripheral speed of 2 m/sec., 
using a ring-on-ring tester. Table 9 shows the results of this experiment. 
Sample Nos. 1-1 to 1-7 are inventive samples, and Sample Nos. 1-8 and 1-9 
are comparative samples. 
TABLE 9 
______________________________________ 
Seizure 
Load 
No. Sliding Material (kg/cm.sup.2) 
______________________________________ 
Inventive 
1-1 Alumina 56 
Sample 1-2 Silicon Carbide 72 
1-3 Silicon Nitride 87 
1-4 Boron Nitride 103 
1-5 Carbon Fiber Reinforced Silicon 
92 
Nitride 
1-6 Silicon Carbide Whisker 
75 
Reinforced Alumina 
1-7 Silicon Carbide Nanoparticle 
79 
Dispersion-Strengthened Alumina 
Comparative 
1-8 Spheroidal Graphite Cast Iron 
2 
Sample 1-9 Bearing Steel 5 
______________________________________ 
As can be seen from the results shown in Table 9, it has been proved that 
the seizure loads were extremely high in the inventive samples, in which 
the first members forming the sliding surfaces were made of ceramics 
(monolithic ceramics, composite materials), as compared with the 
comparative samples. Thus, it has been recognized that seizure is hardly 
caused in the inventive samples even in an atmosphere of a cooling medium 
containing fluorine. 
Further, the sliding surfaces were examined in detail, whereby it was found 
that films mainly composed of carbon were formed on the surfaces. Each of 
the films mainly composed of carbon contained about 70 weight % of carbon 
(C), about 20 weight % of oxygen (O) and a remainder made of elements 
forming the slide member. 
Example 7 
Rings were respectively prepared from mullite, silicon carbide, silicon 
nitride, aluminum nitride, boron carbide, alumina fiber reinforced 
crystallized glass, silicon carbide whisker reinforced silicon nitride, 
silicon carbide nanoparticle dispersion-strengthened silicon nitride, 
flake graphite cast iron and aluminum. Each pair of rings of the same 
material was arranged and driven to slide with each other, for measuring 
the seizure load in a three-type mixture substitutional fluorocarbon 
solution of HCFC22/HFC152a/HCFC124 using a a ring-on-ring tester under a 
peripheral speed of 3 m/sec. while varying the load. In this measurement, 
the surface roughness levels of the sliding surfaces were varied in a 
range of 0.01 to 3 .mu.m Ra, to evaluate seizure loads at respective 
surface roughness levels. In the case of a pair of ceramic rings sliding 
with each other, a seizure load was determined at a point of time when an 
echo was generated during the test and vibration took place in the tester. 
The results of this experiment are shown in Table 10. Referring to the 
Table, Sample Nos. 2-1 to 2-8 are inventive samples, and Sample Nos. 2-9 
and 2-10 indicate comparative samples. 
TABLE 10 
__________________________________________________________________________ 
Seizure Load (kg .multidot. cm.sup.2) 
Sliding Sliding Surface Roughness 
No. Material 3 .mu.mRa 
0.5 .mu.mRa 
0.1 .mu.mRa 
0.01 .mu.mRa 
__________________________________________________________________________ 
Inventive 
2-1 
Mullite 25 61 88 110 
Sample 2-2 
Silicon Carbide 
37 80 115 146 
2-3 
Silicon Nitride 
43 95 143 178 
2-4 
Aluminum Nitride 
31 72 102 127 
2-5 
Boron Carbide 
39 83 117 146 
2-6 
Alumina Fiber 
33 75 103 125 
Reinforced 
Crystallized 
Glass 
2-7 
Silicon Carbide 
43 91 139 172 
Whisker 
Reinforced 
Silicon Nitride 
2-8 
Silicon Carbide 
42 89 128 159 
Nanoparticle 
Dispersion- 
Strengthened 
Silicon Nitride 
Comparative 
2-9 
Flake Graphite 
1 2 3 3 
Sample Cast Iron- 
2-10 
Aluminum 1 1 2 2 
__________________________________________________________________________ 
As can be seen from the results of the experiment shown in Table 10, the 
seizure loads were extremely high in the inventive samples, in which 
members forming the sliding surfaces were made of ceramics (monolithic 
ceramics, composite materials), as compared with the comparative samples. 
Thus, it has been proved that seizure of the sliding surfaces is hardly 
caused in the inventive samples also in an atmosphere of a cooling medium 
containing fluorine. Further, it has been proved that the load at which 
seizure occurs is increased as the surface roughness is reduced. 
Particularly, it has been proved that the seizure load is extremely 
increased when the surface roughness is not more than 0.1 .mu.m Ra. 
Example 8 
In swash plate compressors for car air conditioners, shoes that are to be 
in contact with swash plates made of carbon fiber reinforced carbon 
composite materials were respectively prepared from silicon nitride, boron 
nitride, titanium nitride particle dispersion-strengthened silicon nitride 
and bearing steel. These shoes were employed for evaluating peripheral 
speeds at which seizure resulted between the shoes and the swash plates 
while using HFC134a as a cooling medium and polyalkylene glycol as a 
lubricant. At this time, surface roughness levels of sliding surfaces of 
the shoes were set at 0.1 .mu.m Ra. Determinations as to whether or not 
the shoes seized were made based on the occurrence of abnormal sounds and 
abnormal increases of driving current values. The results of this 
experiment are shown in Table 11. Referring to the Table, Sample Nos. 3-1 
to 3-3 are inventive samples, and Sample No. 3-4 is a comparative sample. 
TABLE 11 
______________________________________ 
Seizure 
Peripheral 
No. Material of Shoe Speed (m/sec.) 
______________________________________ 
Inventive 
3-1 Silicon Nitride 20 
Sample 3-2 Boron Nitride 18 
3-3 Titanium Nitride Particle 
21 
Dispersion-Strengthened 
Silicon Nitride 
Comparative 
3-4 Bearing Steel 4 
Sample 
______________________________________ 
As can be seen from Table 11, it has been proved that seizure is caused at 
extremely high peripheral speeds in the inventive samples in which the 
materials for the shoes were made of ceramics (monolithic ceramics, 
composite materials), as compared with the comparative sample. Thus, it 
has been proved that the sliding surfaces hardly seize in the inventive 
samples also during cooling by a cooling medium containing fluorine. 
Example 9 
A disk of silicon nitride, a disk which was prepared by depositing a carbon 
film of 1.0 .mu.m in thickness on a surface of a disk of silicon nitride 
for forming a sliding surface, and a disk of bearing steel were prepared 
respectively. Further, rings to be in contact with sliding surfaces of the 
aforementioned respective disks were prepared from bearing steel. The 
respective disks and rings were arranged and driven to slide in an 
atmosphere of HFC134a. At this time, seizure loads were measured using a 
ring-on-disk friction tester while varying the applied loads under a 
peripheral speed of 1 m/sec. The results of this experiment are shown in 
Table 12. Surface roughness values in Table 12 indicate those of base 
materials for the disks. Surface roughness values of the sliding surfaces 
of the disks which were provided with carbon films were maintained below 
the values in the Table. 
TABLE 12 
______________________________________ 
Seizure 
Surface Load 
No. Sliding Material 
Roughness (kgf/cm.sup.2) 
______________________________________ 
Inventive 
4-1 Silicon Nitride 
0.5 .mu.mRa 
44 
Sample covered with 
Carbon Film 
4-2 Silicon Nitride 
0.05 .mu.mRa 
71 
covered with 
Carbon Film 
Comparative 
4-3 Silicon Nitride 
3 .mu.mRa 
12 
Sample covered with 
Carbon Film 
4-4 Silicon Nitride 
0.5 .mu.mRa 
32 
4-5 Bearing Steel 
0.5 .mu.mRa 
2 
______________________________________ 
As can be seen from Table 12, it has been proved that seizure loads were 
higher in the inventive samples, in which first members forming the 
sliding surfaces were prepared from carbon films, as compared with the 
comparative samples. Thus, it has been proved that seizure is hardly 
caused in the sliding surfaces of the inventive samples also in an 
atmosphere of a cooling medium containing fluorine. 
Example 10 
Disks were prepared by forming diamond-like carbon films of 3 .mu.m in 
thickness on sliding surfaces of respective disks of silicon nitride and 
high-speed steel by CVD. Further, disks of silicon nitride were prepared. 
Rings comprising sliding surfaces to be in contact with those of the 
respective disks were prepared from bearing steel. The respective disks 
and rings were arranged and driven to slide in liquid HFC134a. At this 
time, seizure loads were measured through a ring-on-disk friction tester 
while varying the applied loads under a peripheral speed of 1 m/sec. The 
results of this experiment are shown in Table 13. Surface roughness values 
appearing in Table 13 indicate those of base materials for the disks. 
Surface roughness values of the sliding surfaces of the disks provided 
with the carbon films were maintained below the values appearing in the 
Table. 
TABLE 13 
__________________________________________________________________________ 
Surface 
Seizure Load 
No. 
Sliding Material 
Roughness 
(kgf/cm.sup.2) 
__________________________________________________________________________ 
Inventive 
5-1 
Silicon Nitride covered 
0.5 .mu.mRa 
64 
Sample with Diamond-Like Carbon 
5-2 
Silicon Nitride covered 
0.05 .mu.mRa 
96 
with Diamond-Like Carbon 
Comparative 
5-3 
Silicon Nitride covered 
3 .mu.mRa 
15 
Sample with Diamond-Like Carbon 
5-4 
High-Speed Steel covered 
0.5 .mu.mRa 
2.3 
with Diamond-Like Carbon 
5-5 
Silicon Nitride 
0.5 .mu.mRa 
32 
__________________________________________________________________________ 
As can be seen from Table 13, seizure loads were extremely high in the 
inventive samples, in which first members forming the sliding surfaces had 
the diamond-like carbon films, as compared with the comparative samples. 
Thus, it has been proved that the sliding surfaces hardly seize in the 
inventive samples also in an atmosphere of a cooling medium containing 
fluorine. 
Example 11 
Disks were respectively prepared from alumina, zirconia, silicon carbide, 
silicon nitride, aluminum nitride and high-speed steel, and surface 
roughness values of sliding surfaces were finished to be 0.05 .mu.m Ra, 
0.5 .mu.m Ra and 3 .mu.m Ra respectively. Rings having sliding surfaces to 
be in contact with those of the respective disks were prepared from flake 
graphite cast iron. The respective disks and rings were arranged and 
driven to slide in gas HFC134a. At this time, a ring-on-disk friction test 
was made under a peripheral speed of 1 m/sec. and a load of 10 kgf, to 
measure the resulting amounts of wear of the disks. The occurrence of 
seizure was determined at a point of time when an echo was generated 
during the test and the tester vibrated. Results of this experiment are 
shown in Table 14. Referring for the Table, rings of bearing steel were 
employed as to comparative samples Nos. 6-7 to 6-11. 
TABLE 14 
__________________________________________________________________________ 
Depth of Wear (.mu.m) 
No. Sliding Material 
3 .mu.mRa 
0.5 .mu.mRa 
0.05 .mu.mRa 
__________________________________________________________________________ 
Inventive 
6-1 
Alumina 10.2 3.1 1.9 
Sample 6-2 
Zirconia 8.9 2.7 1.6 
6-3 
Silicon Carbide 
12.4 4.8 3.2 
6-4 
Silicon Nitride 
2.3 0.5 0.04 
6-5 
Aluminum Nitride 
11.7 4.2 2.8 
Comparative 
6-6 
High-Speed Steel 
Seizure 
Sample 6-7 
Alumina 7.2 
(Ring: Bearing Steel) 
6-8 
Zirconia 6.3 
(Ring: Bearing Steel) 
6-9 
Silicon Carbide 9.4 
(Ring: Bearing Steel) 
6- 
Silicon Nitride 1.5 
10 
(Ring: Bearing Steel) 
6- 
Aluminum Nitride 
8.6 
11 
(Ring: Bearing Steel) 
__________________________________________________________________________ 
As can be seen from Table 14, it has been proved that the inventive 
samples, in which members forming the sliding surfaces were made of 
ceramics and counter members were made of cast iron, were excellent in 
wear resistance. Then, the sliding surfaces were analyzed by ESCA 
(Electron Spectroscopy for Chemical Analysis), whereby it was proved that 
films formed on the sliding surfaces during sliding were mainly composed 
of carbon. From this, it has been proved that the sliding surfaces were 
excellent in wear resistance in the inventive samples having films mainly 
composed of carbon which were formed during sliding. Thus, it has been 
proved that sliding surfaces are excellent in wear resistance in the 
inventive samples also in an atmosphere of a cooling medium containing 
fluorine. 
As hereinabove described, the slide member according to the present 
invention is a slide member having excellent wear resistance, which can be 
used under severe sliding conditions of high-speed sliding or the like. 
Thus, the inventive slide member is useful as a bearing member for a 
high-speed machine which rotates at a high speed or for an office 
automation product. Further, the inventive slide member is useful as a 
sliding component for a compressor of a refrigerator, a freezer or a car 
air conditioner employing a fluorocarbon containing no chlorine as a 
cooling medium. 
Although the invention has been described with reference to specific 
example embodiments, it will be appreciated that it is intended to cover 
all modifications and equivalents within the scope of the appended claims.