JPH0812471A - Ceramic sliding member and method of manufacturing the same - Google Patents

Abstract

(57) [Abstract] [Purpose] A ceramic sliding member provided with a diamond or diamond-like carbon coating having excellent adhesion on the surface of a ceramic sintered body is manufactured by a simple method with good productivity.
In addition, it is formed and provided with a high yield. A ceramic sliding member having a coating of diamond or diamond-like carbon on the surface of a ceramics sintered body containing silicon nitride or sialon as a main component, the ceramics sintered body having the coating. The concentration of Ca in the region at least 100 μm deep from the surface of is lower than the concentration of Ca inside this region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic sliding member in which a diamond or diamond-like carbon coating is provided on the surface of a base material made of a ceramic sintered body, and a method for producing the same.

[0002]

2. Description of the Related Art Ceramics have high hardness and excellent heat resistance and wear resistance. Particularly, ceramics containing silicon nitride or sialon as a main component are excellent in mechanical properties such as strength, toughness and thermal shock resistance. Therefore, it is widely used as a cutting tool, an abrasion resistant tool, and other sliding members.

In recent years, in order to further improve the reliability and life of such ceramics, a coating film of diamond or diamond-like carbon having extremely high hardness, chemical stability and excellent sliding wear resistance is provided as a coating layer. This has attracted attention, and research and development has been actively conducted in many fields. However, a coating film made of diamond or diamond-like carbon has low adhesion to ceramics and has a drawback that the coating film is easily peeled off.

As an attempt to improve the adhesion of diamond or diamond-like carbon coating to ceramics, for example, in Japanese Unexamined Patent Publication No. 5-214532, a cemented carbide or a ceramic sintered body is coated with an aluminum nitride film, It has been proposed to form a diamond or hard carbon coating on top. Further, JP-A-4-254584 discloses that a titanium nitride film having a non-stoichiometric composition is used as an intermediate layer between a cemented carbide or a ceramics sintered body and a diamond or hard carbon coating. .

However, in JP-A-5-214532, the reason why the adhesion of diamond or hard carbon coating is improved by using aluminum nitride for the intermediate layer is to dissolve carbon such as tungsten carbide or titanium carbide in solid solution. If the substance is a base material, it is said that it is possible to prevent the diffusion and solid solution of carbon that occurs during film formation. However, the base material does not contain carbon. A ceramic sintered body such as silicon nitride. No specific explanation has been given for the case.

Further, in JP-A-4-254584, by providing a titanium carbide film having a non-stoichiometric composition with a reduced carbon content as an intermediate layer, carbon is diffused at the interface with a diamond or hard carbon coating. Makes titanium carbide close to the stoichiometric composition, so that carbon diffusion stops on the base material side and titanium carbide remains in the non-stoichiometric composition, so a large volume change does not occur and adhesion to the base material Is said to improve.

On the other hand, Japanese Patent Application Laid-Open No. 4-202075 discloses forming a diamond or diamond-like carbon coating after treating the surface of a sintered body containing silicon nitride as a main component with an acid or an alkali. There is. By treatment with an acid or an alkali, the grain boundaries on the surface of the silicon nitride sintered body and the vitreous in the vicinity of the grain boundaries are preferentially corroded to leave columnar particles of silicon nitride, forming fine irregularities and nitriding the surface. It is described that since the area ratio of silicon increases, the coefficient of thermal expansion of the surface of the base material becomes closer to that of diamond, and high adhesion can be obtained.

[0008]

However, even in the above-mentioned conventional method, it was difficult to sufficiently improve the adhesion between the ceramic sintered body and the diamond or diamond-like carbon coating. That is, in the method of providing the intermediate layer such as aluminum nitride or titanium carbide, the number of coatings and the number of coatings are increased by forming the intermediate layer,
Delamination is more likely to occur between the interlayers and between the interlayer and the diamond or diamond-like carbon coating.

Further, according to the method of treating the ceramics sintered body with an acid or an alkali, it is difficult to form a coating film of diamond or diamond-like carbon along the fine irregularities on the surface, and the glass phase of the grain boundary is melted. The coating does not sufficiently wrap around inside the formed pores, so that the expected improvement in adhesion cannot be obtained.

Further, in the case of the method of treating the ceramics sintered body with acid or alkali, since hydrofluoric acid, hydrofluoric nitric acid, sodium hydroxide or the like is used, not only management of these but also safety and environmental measures can be taken. Will be needed. In addition, it is also necessary to strictly control the conditions of corrosion treatment with acid or alkali, and if the glass phase of the ceramics sintered body is over-melted or over-melted, it causes a decrease in adhesiveness. This may cause a decrease in yield.

In view of the above conventional circumstances, the present invention provides a ceramic sliding member having a coating of diamond or diamond-like carbon with excellent adhesion on the surface of a ceramic sintered body, and the ceramic sliding member. An object of the present invention is to provide a method for forming a sliding member by a simple method with high productivity and high yield.

[0012]

In order to achieve the above object, the ceramic sliding member provided by the present invention has a diamond or diamond-like structure on the surface of a ceramic sintered body containing silicon nitride or sialon as a main component. In a ceramic sliding member provided with a carbon coating, the Ca concentration in a region at a depth of at least 100 μm from the surface of the ceramic sintered body provided with the coating is higher than the Ca concentration in the inside of this region. It is characterized by decreasing.

The method for producing a ceramic sliding member of the present invention comprises subjecting a ceramic sintered body containing silicon nitride or sialon as a main component to heat treatment in a vacuum,
The present invention is characterized in that a Ca or diamond-like carbon film is formed on the surface of the ceramic sintered body after the Ca component in the region at a depth of at least 100 μm is eliminated or reduced.

The diamond-like carbon referred to here is
It means carbon that is amorphous and has properties similar to diamond. In English, diamond-like carbon.
Is called.

[0015]

In the present invention, attention is paid to a slight amount of impurities, particularly calcium compounds, contained in the silicon nitride powder, which is the raw material of the ceramics sintered body containing silicon nitride or sialon as the main component, from the surface of the sintered body or its vicinity. By eliminating or reducing the calcium compound, it was possible to improve the adhesion between the ceramic sintered body and the diamond or diamond-like carbon coating.

That is, the ceramic sintered body containing silicon nitride (Si ₃ N ₄ ) or sialon (SiAlON) as a main component has an appropriate particle size, purity, α ratio, and aspect ratio depending on the intended use. It is produced by using a commercially available silicon nitride powder having, for example, and adding and mixing a sintering aid to the powder, and the silicon nitride powder contains a small amount of impurities such as oxygen, in addition to Si ₃ N ₄ . It contains carbon, chlorine, iron, calcium, aluminum, etc.

These impurities are mixed in from equipment or jigs used for producing the silicon nitride powder, or are already contained in the solid or liquid as a raw material for producing the silicon nitride powder. However, it is extremely difficult to eliminate all of them.

Therefore, the ceramic sintered body containing silicon nitride or sialon as a main component contains these impurities, and when X-ray analysis is performed on the surface and the inside,
Y ₂₀ N ₄ Si ₁₂ O ₄₈ and Ca (Fe, M)
g) It was found that Si ₂ O ₆ was formed. When this ceramics sintered body is heat-treated in vacuum, these compounds remain inside the sintered body, but only Y ₂₀ N ₄ Si ₁₂ O ₄₈ remains on the surface of the sintered body, and Ca (Fe, Mg)
It was found that Si ₂ O ₆ disappeared.

Therefore, a diamond coating and a diamond-like carbon coating are formed on the surface of each of the ceramics sintered body that has been previously heat-treated in vacuum and the ceramics sintered body that is not heat-treated, and the adhesion is pin-on- When evaluated by the disk test method, the ceramics sintered body which had been previously heat-treated in vacuum showed about three times the adhesion as compared with the sintered body without heat treatment.

The reason for this is not clear, but it can be considered as follows. As shown in Table 1, Ca and Mg have a higher ionic bond property with respect to the bond with oxygen than Si, and also have a weak bond force. Therefore, when heat treatment is performed in a vacuum, Ca and Mg having high ionic bond properties disappear from the surface of the ceramics sintered body, so that the ionic bondability is weakened in the vicinity of the surface of the sintered body and the covalent bondability becomes high.

[0021]

[Table 1] Element ion bondability (%) Single bond strength (kJ / mol) Si 37 444 Ca 62 134 Mg 55 155

It is known that both diamond and diamond-like carbon are sp ³ hybrid orbits and exhibit covalent bondability. Therefore, the coating film of diamond or diamond-like carbon exhibiting a covalent bond is excellent in adhesiveness because it is bonded to the surface of a sintered product having a high covalent bond more strongly than the surface of a sintered product having an ionic bond. It is considered that the formation of the coating has become possible.

The sintered body containing silicon nitride or sialon as a main component is heat-treated in vacuum, and then Y in the sintered body is used.
The elemental analysis of ₂₀ N ₄ Si ₁₂ O ₄₈ and Ca (Fe, Mg) Si ₂ O ₆ and the adhesion of diamond or diamond-like carbon coating were evaluated by the pin-on-disk test method. In order that the adhesiveness when heat-treated at 10 is superior to the adhesiveness when not heat-treated, Ca (Fe,
It was found that the concentration distribution of Mg) Si ₂ O ₆ , that is, the concentration distribution of the Ca component, needs to be reduced from the region at least 100 μm deep from the surface of the sintered body.

The heat treatment in vacuum for obtaining the improved adhesion of the diamond or diamond-like coating due to the disappearance or reduction of the Ca component is preferably 10 ^-3 Pa.
Perform in the following vacuum. If the atmosphere during the heat treatment exceeds 10 ^-3 Pa, an oxide film is formed on the surface of the sintered body, and it becomes difficult for the Ca and Mg components to dissipate from the surface of the sintered body even by the heat treatment. The effect of the present invention cannot be expected.

The conditions of heat treatment in vacuum are 1100 to 14
It is preferable to carry out at a temperature of 00 ° C. for 2 to 6 hours. If the conditions are a temperature of less than 1100 ° C. or a heat treatment time of less than 2 hours, the surface of the sintered body is not effectively modified and the adhesion of the diamond or diamond-like carbon coating is not sufficiently improved.
On the contrary, if the temperature exceeds 1400 ° C. or the heat treatment time exceeds 6 hours, silicon nitride may be sublimated.

Further, by performing the heat treatment in vacuum, it is possible to crystallize the grain boundary phase of the sintered body containing silicon nitride or sialon as a main component, and in that case, if necessary, The heat treatment temperature and time pattern may be adjusted. Crystallization of the grain boundary phase by this heat treatment improves the strength of the sintered body at high temperatures.

In the present invention, the ceramic sintered body is a ceramic containing silicon nitride or sialon as a main component, and other ceramic components such as silicon carbide (SiC), zirconia (ZrO ₂ ) and titanium carbide (T
iC), hafnium carbide (HfC), etc. may be contained. It may also include whiskers such as silicon carbide whiskers, silicon nitride whiskers, and carbon whiskers.

The powder raw material of the ceramics sintered body containing silicon nitride or sialon as a main component contains impurities as described above, and the content thereof is the method for producing the silicon nitride powder by the direct nitriding method or the imide decomposition method or the powder. It depends on the refining method of. In particular, the content of Ca is about 0.5 ppm to 2% by weight in a commercially available silicon nitride powder, but in order to achieve the effect of the present invention, the content of Ca as an impurity is 1 pp.
It is preferably in the range of m to 1% by weight. When the Ca content in the sintered body is 1 ppm or more, the effect of improving the adhesion of the coating by the vacuum heat treatment of the present invention becomes remarkable, and when it exceeds 1% by weight, a sintered body sufficiently dense as a sliding member is obtained. Because you will not be able to get it.

In the production of a ceramic sintered body containing silicon nitride or sialon as a main component, a sintering aid is added to silicon nitride powder for sintering. It goes without saying that an agent can be contained. Examples of such a sintering aid include yttrium oxide (Y
₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), aluminum nitride (AlN), zirconium oxide (Zr ₂ O ₃ ), magnesium oxide (MgO), erbium oxide (Er)
₂ O ₃ ), dysprosium oxide (Dy ₂ O ₃ ), titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ), ytterbium oxide (Yb ₂ O ₃ ), and the like.

The size of the ceramics sintered body is not limited, and may be cylindrical, rod-shaped, hollow, having pores, or any other complicated shape. Such a ceramics sintered body may be subjected to polishing, lapping, etc., depending on the purpose of use, prior to forming the coating film.

Any known method can be used to form a coating film of diamond or diamond-like carbon on the surface of the ceramics sintered body containing silicon nitride or sialon as the main component, which has been heat-treated in vacuum. However, it is preferable from the practical and production viewpoints to use various vapor phase synthesis methods such as the CVD method, the combustion flame method, the ion plating method, and the sputtering method.

Specifically, in the vapor phase synthesis method, a raw material gas containing a carbon source gas is excited in a reaction chamber to form a diamond or diamond-like carbon film on the sintered body. As the carbon source gas, in addition to various hydrocarbons, carbon compounds containing nitrogen, halogen, oxygen and the like, or a mixture thereof are used, and if necessary, mixed with hydrogen, argon, helium and the like. Excitation methods of the source gas include RF plasma CVD method, DC plasma CVD method, microwave plasma CVD method, hot filament CVD method, and thermal CVD method.
Method, plasma flash method, and thermal plasma method.

[0033]

Example 1 A commercially available Si ₃ N ₄ powder having a particle size (median size as a median value) and an impurity content shown in Table 2 below was used, and Y ₂ having an average particle size of 1.1 μm was used. O ₃ powder 5% by weight and average particle size 0.6
3% by weight of Al ₂ O ₃ powder having a particle diameter of μm was added, and wet mixing was performed in ethanol by a ball mill for 100 hours.

[0034]

TABLE 2 Properties median size not pure product free chromatic amount of silicon nitride powder (μm) Al O C Ca Fe Cl Mg 0.9 20ppm 1.2wt% 0.1wt% 0.2wt% 20ppm 15ppm 0.01wt%

After drying this mixed powder, 5000 kg
CIP molding was performed at a pressure of / cm ² . 1 for the obtained molded body
It is heated and held at 1600 ° C. for 4 hours in a nitrogen gas atmosphere of atmospheric pressure, and then sintered at 1700 ° C. for 6 hours, and the obtained sintered body is heated at 1700 ° C. in a nitrogen gas atmosphere of 500 atmospheric pressure for 2 hours. HIP treatment for hours was applied.

The silicon nitride sintered body thus obtained was lapped and then placed in a vacuum heat treatment furnace. next,
The inside of the furnace was evacuated to 10 ^-3 Pa, and the test piece was subjected to vacuum heat treatment at 1300 ° C for 3.5 hours. A test piece 1 was prepared by forming a diamond-like carbon coating film having a thickness of 1.1 μm on the surface of the sintered body subjected to the vacuum heat treatment by using the RF plasma CVD method. The conditions for forming the diamond-like carbon film are methane gas as a raw material gas and a pressure of 0.5T.
The output power was 800 W at orr.

For comparison, a comparative test in which a diamond-like carbon film was formed by lapping a silicon nitride sintered body produced in the same manner as above and then heat treating in a nitrogen atmosphere instead of heat treating in vacuum A piece 1a, a comparative test piece 1b having a diamond-like carbon coating formed under the same conditions without vacuum heat treatment, and a comparative test piece 1c having no diamond-like carbon coating by lapping were prepared. The heat treatment conditions in the nitrogen atmosphere were the same as in the vacuum at 1300 ° C. for 5 hours, and the treatment was carried out at atmospheric pressure.

These test pieces 1 and comparative test pieces 1a, 1
b, 1c according to the pin-on-disk test method, load 20 N, sliding speed 150 mm / sec, sliding number 5
A sliding test was conducted under the condition of 0000 times. As a result, the friction coefficient was determined by comparing the comparative test piece 1c without the diamond-like carbon coating.
However, the test piece 1 of the present invention, the test piece 1a heat-treated in a nitrogen atmosphere, and the comparative test piece 1b having a diamond-like carbon coating formed without heat treatment were both 0.2. It was

However, the wear depth was 8 μm for the comparative test piece 1c and 3 μm for the comparative test pieces 1a and 1b, whereas it was 0.8 μm for the test piece 1 of the present invention. Further, although the peeling of the diamond-like carbon coating was observed in the comparative test piece 1a formed with a film after heat treatment in a nitrogen atmosphere and the comparative test piece 1b formed with a film without heat treatment, the test piece 1 of the present invention showed a peeling. No peeling was observed. From these results, it was found that in the test piece 1 of the present invention in which the diamond-like carbon coating was formed after the vacuum heat treatment, the coating adhesion was remarkably improved.

On the other hand, the same silicon nitride sintered body as above, which has been heat-treated in vacuum according to the present invention,
Using an X-ray microanalyzer (EPMA), the element distribution in the grain boundary phase was investigated in the depth direction for the sintered body that was heat-treated in the nitrogen atmosphere and the sintered body that was not heat-treated, and the results are shown in FIG. It was shown to. Fig. 1 shows Y ₂₀ N ₄ Si ₁₂ O ₄₈ and Ca (F
3 is a graph showing the distribution of (e, Mg) Si ₂ O ₆ , where the vertical axis represents Y ₂₀ N ₄ S on the surface of the sintered body that has been subjected to vacuum heat treatment.
It is displayed on a relative scale with the content of i ₁₂ O ₄₈ as 100.

As can be seen from FIG. 1, the sintered body which was heat-treated in the nitrogen atmosphere and the sintered body which was not heat-treated were Y ₂₀ N ₄ Si ₁₂ O ₄₈ and Ca (Fe, Mg) Si ₂ O.
Both ₆ have a uniform distribution in the depth direction, and it was found that heat treatment in a nitrogen atmosphere had no effect. On the other hand, in the sintered body that has been heat-treated in vacuum, both compounds are present inside, but Ca (Fe,
Mg) Si ₂ O ₆ started to decrease gradually from the surface to a depth of about 400 μm and was not detected at all on the surface.

Using a bending test piece made of the same sintered body as in Example 1, heat treatment in vacuum or heat treatment in a nitrogen atmosphere was performed under the same conditions as described above, and the heat treatment was performed with these test pieces. A diamond-like carbon film having a thickness of 1.1 μm was formed by the plasma CVD method under the same conditions after lapping treatment on the test piece which was not subjected.

Using each test piece provided with these diamond-like coatings, at room temperature, 600 ° C., 800 ° C., 900 ° C.,
The transverse rupture strength at 1000 ° C, 1100 ° C, 1200 ° C and 1300 ° C was measured. The result is shown in FIG. As can be seen from these results, the test piece that was heat-treated in vacuum showed the smallest deterioration of the transverse rupture strength even at high temperature, and the test piece that was heat-treated in the nitrogen atmosphere was not heat-treated. It showed the same temperature dependence.

Furthermore, when the crystal structure diffraction of each of these test pieces was examined, peaks due to the crystalline grain boundary phase appeared in addition to the silicon nitride pattern in the test pieces subjected to the heat treatment in vacuum. In the test piece heat-treated in a nitrogen atmosphere, only a few peaks due to the crystalline grain boundary phase appeared except for the pattern of silicon nitride. Moreover, only the peak of silicon nitride was detected in the test piece that was not heat-treated. From these results, heat treatment in vacuum not only improves the adhesion of the diamond-like carbon coating, but also improves the high temperature characteristics due to the crystallization of the grain boundary phase.

Example 2 A commercially available Si ₃ N ₄ powder having a particle size (median size as a median value) and an impurity content shown in Table 3 below was used, and Er ₂ O having an average particle size of 0.8 μm was used. ₃ powder 6% by weight, average particle size 1.
3% by weight of 1 μm AlN powder and 10% by weight of SiC whiskers having a short diameter of 0.4 to 2 μm and a length of 5 to 50 μm were added, wet-mixed and dried as in Example 1.

[0046]

TABLE 3 Properties median diameter not pure product free chromatic amount of silicon nitride powder (μm) Al O C Ca Fe Cl Mg 1.5 30ppm 2.1wt% 0.1wt% 0.6wt% 60ppm 29ppm 0.01wt%

This mixed powder was heated to 200 atm and 1750 ° C.
Hot press sintering was performed for 2 hours to produce a silicon nitride sintered body. The silicon nitride sintered body thus obtained was lapped, then placed in a vacuum heat treatment furnace, the furnace was evacuated to 10 ⁻⁴ Pa, and vacuum heat treatment was performed at 1400 ° C. for 2.5 hours.

On the surface of the sintered body subjected to the vacuum heat treatment,
A diamond-like carbon coating film having a thickness of 0.6 μm was formed by using the RF plasma CVD method to obtain a test piece 2 of the present invention.
The conditions for forming this diamond-like carbon film were such that methane gas was used as a raw material gas, the pressure was 0.8 Torr, and the output power was 600 W.

For comparison, after lapping the silicon nitride sintered body manufactured in the same manner as described above, a comparative test piece 2a having a diamond-like carbon coating formed under the same conditions without vacuum heat treatment was used. A comparative test piece 2b was prepared by performing only the treatment and forming no diamond-like carbon coating.

These test pieces 2 and comparative test pieces 2a, 2
Using b, a sliding test was conducted under the same conditions as in Example 1. As a result, the coefficient of friction was 1.3 for the comparative test piece 2b without the diamond-like carbon coating, but was 0.2 for both the test piece 2 of the present invention and the comparative test piece 2a formed with no vacuum heat treatment. It was 2.

However, the wear depth was 9 μm for the comparative test piece 2b and 2 μm for the comparative test piece 2a, whereas the test piece 2 of the present invention was much less at 0.4 μm, and the vacuum heat treatment was performed. Although the peeling of the diamond-like carbon coating was observed in the comparative test piece 2a having the coating formed without it, the peeling of the coating was not observed in the test piece 2 of the present invention. From these results, it was found that in the test piece 2 of the present invention in which the diamond-like carbon coating was formed after the vacuum heat treatment, the coating adhesion was remarkably improved.

Example 3 A silicon nitride sintered body produced in the same manner as in Example 2 was ground and then placed in a vacuum heat treatment furnace, and the inside of the furnace was ^heated to 10 ⁻⁴ P.
It was evacuated to a and subjected to vacuum heat treatment at 1200 ° C. for 4 hours. A pin-on-disk test piece 3a was prepared by forming a diamond coating having a thickness of 5 μm on the surface of the sintered body subjected to the vacuum heat treatment by using the RF plasma CVD method. For comparison, a comparative test piece 3b having a diamond coating formed under the same conditions was prepared by grinding the silicon nitride sintered body produced as described above and then performing no vacuum heat treatment.

Using these test pieces 3a and 3b, sliding tests similar to those in Examples 1 and 2 were conducted. As a result, no peeling of the diamond coating was observed in the test piece 3a according to the present invention, but large peeling was observed in the comparative test piece 3b. From these results, it was found that in the test piece 3a of the present invention in which the diamond coating was formed after the vacuum heat treatment, the coating adhesion was improved.

Further, regarding these test pieces 3a and 3b,
Y ₂₀ N ₄ Si ₁₂ O ₄₈ in the depth direction from the surface of the sintered body
And Ca (Fe, Mg) Si ₂ O ₆ distributions were measured as in Example 1. As a result, although both compounds were present inside the test piece 3a of the present invention, Ca (F
e, Mg) Si ₂ O ₆ started to decrease gradually from the surface to a depth of about 350 μm and was not detected at all on the surface. On the other hand, in the comparative test piece 3b, both compounds were found to have a constant distribution in the depth direction.

Example 4 Two kinds of commercially available Si ₃ N ₄ powders having the particle size (median size as the median value) and the impurity content shown in Table 4 below were used,
4% by weight of Al ₂ O ₃ powder having an average particle size of 0.8 μm, 4% by weight of AlN powder having an average particle size of 1.0 μm, and Y ₂ O ₃ powder 3 having an average particle size of 0.8 μm were added to each Si ₃ N ₄ powder. Weight% was added and wet mixing was performed in ethanol for 100 hours with a ball mill.

[0056]

TABLE 4 Characteristics powder median diameter not pure product free chromatic amount kinds of silicon nitride powder (μm) Al O C Ca Fe Cl Mg A 0.7 30ppm 2.5wt% 0.1wt% 0.1wt% 50ppm 18ppm 0.01wt% B 0.7 28ppm 2.6 wt% 0.13wt% 1.5wt% 47ppm 18ppm 0.01wt%

After drying this mixed powder, 5000 kg
CIP molding was performed at a pressure of / cm ² . 1 for the obtained molded body
It is heated and held at 1600 ° C. for 4 hours in a nitrogen gas atmosphere at atmospheric pressure, and then sintered at 1800 ° C. for 5 hours, and the obtained sintered body is heated at 1750 ° C. in a nitrogen gas atmosphere at 1000 atmospheric pressure for 2 hours. HIP treatment for hours was applied.

When the structure of each of the silicon nitride sintered bodies thus obtained was observed and the density was measured, the sintered body using the powder A had no defects and had a density of 3.24 g / cm ³ and was sufficiently densified. I found out. However, the sintered body using the powder B has many defects such as pores on the surface and inside and has a density of 3.11.
It was not fully densified with g / cm ³ .

Next, the sintered body produced by using this powder A was processed for a pin-on-disk test, lapped, and then placed in a vacuum heat treatment furnace so that the inside of the furnace was 10 ^-3 Pa.
Vacuum evacuation was performed and the test piece was held at 1150 ° C. for the time conditions shown in Table 5 below to perform vacuum heat treatment.
In this case, in the test piece subjected to the vacuum heat treatment at 1150 ° C. for 8 hours under the condition 5, the silicon nitride near the surface was sublimated, and the shape of the test piece before the heat treatment was not retained.

A diamond-like carbon coating having a thickness of 1.5 μm was formed on the surface of the test piece which had been subjected to the vacuum heat treatment under the conditions 1 to 4 by the RF plasma CVD method. These test pieces were subjected to a pin-on-disk test under the same conditions as in Example 1, and the results of evaluating the friction coefficient and the wear depth thereof are also shown in Table 5. In addition, these test pieces were cut perpendicularly to the test surface, and Ca in the depth direction from the test surface was cut.
The changes in the concentrations of the components were measured by EPMA, and the results are shown in FIG. 3, and the depth from the surface of the starting point where the Ca concentration is lowered was obtained and shown in Table 5.

[0061]

[Table 5] Condition 1 Condition 2 Condition 3 Condition 4 Condition 5 Holding time (H) 0.5 1.0 2.0 5.0 8.0 Abrasion coefficient 0.9 0.8 0.3 0.2 − Abrasion depth (μm) 2.7 2.6 0.8 0.8 − Delamination of film Exfoliation No exfoliation No exfoliation-Ca concentration lowering point (μm) 30 80 110 340- (Note) Under condition 5, silicon nitride near the surface sublimated.

From these results, the diamond-like carbon coating is peeled off when the Ca concentration is not lowered from the place 100 μm or more deeper than the surface of the sintered body as in the conditions 1 and 2, whereas the diamond-like carbon coating is peeled off. When the Ca concentration is lower than 100 μm or more deeper than the surface of the sintered body as in the conditions 3 and 4, peeling of the diamond-like coating does not occur, the adhesion of the coating is improved, and the wear depth It can also be seen that it is smaller than the conditions 1 and 2.

[0063]

According to the present invention, a highly adherent diamond or diamond-like carbon coating is formed on the surface of a ceramics sintered body containing silicon nitride or sialon as a main component by a simple method with high productivity, and It is possible to provide a ceramic sliding member which can be formed with a high yield and therefore has a highly adherent coating of diamond or diamond-like carbon on its surface.

[Brief description of drawings]

FIG. 1 shows Y ₂₀ N ₄ Si ₁₂ O in the depth direction from the surface of the sintered body for each sintered body under different heat treatment conditions in Example 1.
₄ is a graph showing concentration distributions of ₄₈ and Ca (Fe, Mg) Si ₂ O ₆ .

FIG. 2 is a graph showing the relationship between the transverse rupture strength of a sintered body and the measured temperature for each sintered body under different heat treatment conditions in Example 1.

FIG. 3 shows Ca (Fe, M in the depth direction from the surface of the sintered body for each sintered body under different heat treatment conditions in Example 4.
g) A graph showing the concentration distribution of Si ₂ O ₆ .

Claims (5)

[Claims] 1. A ceramics sliding member having a coating of diamond or diamond-like carbon on the surface of a ceramics sintered body containing silicon nitride or sialon as a main component. The ceramic sliding member is characterized in that the Ca concentration in a region at a depth of at least 100 μm from the surface is lower than the Ca concentration inside the region. 2. A ceramic sintered body containing silicon nitride or sialon as a main component is heat-treated in a vacuum to remove at least 10 from the surface of the ceramic sintered body.
A method for producing a ceramic sliding member, characterized in that after a Ca component in a region having a depth of 0 μm is eliminated or reduced, a coating film of diamond or diamond-like carbon is formed on the surface thereof. 3. The method for producing a ceramic sliding member according to claim 2, wherein the heat treatment is performed in a vacuum of 10 ⁻³ Pa or less. 4. The method for producing a ceramic sliding member according to claim 2, wherein the heat treatment is performed at a temperature of 1100 to 1400 ° C. for 2 to 6 hours. 5. The silicon nitride or sialon powder, which is a starting material for a ceramics sintered body, contains 1 ppm to 1% by weight of a Ca compound in terms of Ca, and any one of claims 2 to 4 is characterized. A method for producing a ceramic sliding member as described in 1.