JPH0550475B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to ceramics for sliding materials, and particularly to ceramics for sliding materials that have excellent wear resistance and thermal shock resistance. [Conventional technology] When a machine moves, there is always sliding movement. Reducing friction and wear on sliding parts will lead to energy savings and longer life. Oil is generally used to lubricate sliding parts. Since oil has a high viscosity, if there is relative speed between the sliding surfaces, an oil film will be formed and no wear will occur. Furthermore, oil lubrication also has a cooling effect. Oil is an ideal lubricant when focusing only on reducing friction and wear. However, oil lubrication requires an oil flow path and an oil sump, which makes the machine larger and more complicated, leading to higher costs. Oil and grease evaporate and deteriorate, requiring maintenance. Also, oil evaporates rapidly, especially at high temperatures in a vacuum. Moreover, the evaporated oil contaminates surrounding equipment. Machines are required to be small, lightweight, low cost, and maintenance-free. Solid lubrication meets these expectations. Graphite materials have been known as sliding materials that can be used up to high temperatures without lubrication. Graphite material has excellent chemical resistance and self-lubricating properties, so
Although it can be used up to high temperatures without lubrication, its major disadvantage is that it has a large porosity and poor mechanical strength.Although resin-filled graphite materials and boron nitride have a small coefficient of friction, they have extremely low wear resistance and poor mechanical strength. Because of their small size, their lifespans were short and the sliding members had to be replaced frequently. In addition, solid lubricant-dispersed sintered metals, which have graphite, molybdenum disulfide, etc. uniformly dispersed in the metal base material, are also used, but because the base material is metal, they have poor chemical resistance and corrosion resistance, and are resistant to wear at high temperatures. It has disadvantages such as being inferior in sex. On the other hand, sliding members made of ceramics have been provided in recent years, but the coefficient of friction of general ceramics is
The value is 0.5 or more, and in some cases it may exceed 1, which places great restrictions on devices using ceramic sliding members. They are called engineering ceramics, and silicon carbide, silicon nitride, alumina, and zirconia are known as typical examples, but they must satisfy the following required characteristics in order to be actually used as sliding materials. (References: Industrial Materials, Vol.
(Volume 31, No. 12, Page 140) (1) High hardness, excellent wear resistance and seizure resistance (2) Good compatibility with sliding mating material (low coefficient of friction, (3) Excellent corrosion resistance (4) High strength, toughness, and thermal shock resistance (5) In order to maintain good lubrication between sliding surfaces, Small deformation of the sliding surface (that is, high Young's modulus and low coefficient of thermal expansion) (6) High thermal conductivity (high thermal shock resistance and prevention of frictional heat accumulation (7) Low specific gravity (reducing centrifugal stress) Looking at the suitability of existing materials for these required properties, metallic materials have problems with seizure resistance. There is. Alumina ceramics alone has poor thermal shock resistance.
Since the coefficient of thermal expansion is large, the sliding surface is deformed due to heat. Like alumina, zirconia alone has poor thermal shock resistance and a large coefficient of thermal expansion. Silicon nitride alone has low hardness and low thermal conductivity. Silicon carbide alone has problems such as being hard and having excellent thermal conductivity, but poor thermal shock resistance.There is a need for a sliding material that has both abrasion resistance and corrosion resistance, as well as further improved thermal shock resistance. has been done. [Problems to be solved by the invention] The above-mentioned conventional technology does not give consideration to wear resistance and thermal shock resistance, causes large wear with the mating material, and is susceptible to cracking caused by rapid temperature changes. There was a problem that it caused An object of the present invention is to provide ceramics for sliding materials that can be used without oil and at high temperatures, have wear resistance, particularly reduce wear on mating materials, and have excellent thermal shock resistance. [Means for Solving the Problems] To summarize the present invention, the present invention relates to ceramics for sliding materials, and is a composite ceramic of silicon nitride and silicon carbide with a pore size of 200 μm or less, in which a solid lubricant is applied. It is characterized by being present in an amount of 1 to 40 parts by volume. In the present invention, the ceramic sliding material is a sintered body mainly composed of silicon nitride and silicon carbide. The reason for this is that by combining silicon carbide, which has excellent wear resistance, hardness, and thermal conductivity, with silicon nitride, which has a small coefficient of thermal expansion, a sliding material that has the characteristics of both silicon nitride and silicon carbide can be obtained. This is because it will be done. Further, by combining silicon carbide and silicon nitride, it is possible to obtain unprecedented thermal shock resistance. In the present invention, the method of making the solid lubricant exist in the pores of the sintered body includes a method of mixing the solid lubricant together with the ceramic raw material, molding, and sintering;
and a method in which the solid lubricant is impregnated into a sintered body under pressure, and the solid lubricant can be uniformly dispersed. In the present invention, when a solid lubricant is added together with the raw materials, the amount of the solid lubricant in the ceramic sintered body is 1 to 40 parts by volume. The reason is 1.
This is because if the amount is less than 40 parts by volume, there is almost no effect, whereas if it is more than 40 parts by volume, there is an effect, but the ceramic sintered body becomes porous and has low strength, which is not preferable. In the present invention, when the solid lubricant is impregnated into the sintered body, the solid lubricant is added to the ceramic sintered body at a depth of at least 0.5 mm in the surface layer of the ceramic sintered body.
Preferably, the amount is 40 parts by volume. The reason is that if the amount is less than 1 part by volume, there is almost no effect;
This is because impregnation is difficult if the amount exceeds 40 parts by volume. Also, the solid lubricant should have a surface layer of at least 0.5
If it is impregnated with 0.5 mm or more, the solid lubricant will come out onto the sliding surface and lower the friction coefficient of the sliding surface, so it may be impregnated as much as possible if it is 0.5 mm or more. Furthermore, in the case of impregnation, it is preferable that the size of one pore in the sintered body is 200 μm or less, and the amount of pores is 1 to 47 parts by volume. The reason for this is that if the pore size is made larger than 200 μm, the amount of cracks generated in the sintered body will increase, and if the pore size is 200 μm, it is sufficient for impregnation. If the amount of pores is greater than 47 parts by volume, the mechanical strength will be too low, making it unsuitable for use as a sliding material. In the present invention, solid lubricants include graphite, molybdenum disulfide, titanium disulfide, tungsten disulfide, boron nitride, fluorine resin, tellurium disulfide, selenium disulfide, barium hydroxide, lead chloride, mica, iodine, etc. Silver oxide, talc, borax, kaolin, lead oxide, zinc oxide, vermiculite, Fe
-Mn-phosphates, polyethylene glycol, paraffin wax, stearic acid compounds, and other materials that have the effect of reducing friction are preferred. In the present invention, the molding method may be any conventional method, such as mold molding, rubber press molding, injection molding, cast molding,
Extrusion molding, hot isostatic press molding, hot press molding, etc. may be appropriately selected depending on the shape and required characteristics. In addition, the sintering method for the compact may be any conventional method, and depending on the required properties, reaction sintering, normal pressure sintering, secondary sintering,
This may be done using a hot press or the like. According to the present invention, the friction coefficient can be reduced by one order of magnitude and the amount of wear can be reduced by one order of magnitude compared to the case of silicon nitride, silicon carbide, alumina, or zirconia alone. Furthermore, the thermal shock resistance can be doubled, thereby providing an excellent sliding material with unprecedented wear resistance and thermal shock resistance. [Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, Comparative Examples, and Reference Examples, but the present invention is not limited to these Examples. Example 1 60 g of metal Si powder with an average particle size of 1 μm and an average particle size of
100 c.c. of 20% polyvinyl alcohol solution was added as a molding aid to a mixture of 40 g of 16 μm silicon carbide powder, mixed in a pot mill for 24 hours, and then dried at room temperature to obtain a test material. This raw material was molded using a mechanical press at a molding pressure of 100 to 1000 Kgf/cm ² into a product having an outer diameter of 30 mm, an inner diameter of 20 mm, and a thickness of 30 mm.
This was sintered stepwise at 1100-1400°C over a long period of time in nitrogen. This ring-shaped sintered body was impregnated with various solid lubricants using an autoclave, and the sliding surface was polished, and then a dry sliding test was conducted under the following conditions. The results are shown in Table 1. Sliding conditions Test machine Mechanical seal type [Ring on Ring] method Lubrication method No lubrication Sliding speed 2m/sec Surface pressure 1.5Kg/cm ² hours 100 hours

【table】

[Table] From this, number 1 without solid lubricant added
It can be seen that the coefficient of dynamic friction and the amount of wear are smaller in the case where a solid lubricant is added compared to the above. Furthermore, as a result of breaking and analyzing a sintered body impregnated with a solid lubricant, it was found that the solid lubricant was uniformly dispersed from the surface of the sintered body to a maximum depth of 10 mm. Example 2 Table 2 shows the results of a thermal shock test conducted on the product of the present invention obtained in Example 1. The thermal shock test is
After holding the sample at each temperature for 20 minutes, the sample was immersed in water at approximately 20°C to check whether or not cracks had occurred in the sample, and the highest temperature that each sample could withstand without cracking was determined.

[Table] Table 3 also shows the results of tests on comparative materials under similar conditions. This result shows that Si ₃ N ₄ -SiC has extremely excellent thermal shock resistance.

[Table] Example 3 A wet sliding test was conducted in the same manner as in Example 1 under the following conditions. The results are shown in Table 4, numbers 1 to 8. Sliding conditions Test machine Mechanical seal type (ring-on-ring method) Lubrication method Oil lubrication (machine oil) Sliding speed 100m/min Surface pressure 5Kg/cm ² hours 100 hours Results of tests on comparative materials under similar conditions is shown in number 9. This shows that the product of the present invention has an extremely small dynamic friction coefficient and wear amount compared to the conventional product.

[Table] Example 4 A sintered body obtained in the same manner as in Example 1 was subjected to a wet sliding test under the following conditions while varying the amount of graphite added. The results are shown in Table 5. Sliding conditions Test machine Mechanical seal type (ring-on-ring method) Lubrication method Oil lubrication (machine oil) Sliding speed 10m/sec Surface pressure 5Kg/cm ² hours 100 hours

[Table] From this table, it can be seen that the coefficient of friction is large and the amount of wear is large when no solid lubricant is added. It is also seen that when the amount added is greater than 40% by volume, the mechanical strength decreases and the amount of wear increases. Example 5 60 g of silicon nitride powder with an average particle size of 1 μm and an average particle size
40g of 2μm silicon carbide powder and 5g of magnesium oxide
Blend 5 g of yttrium oxide, add 100 c.c. of 20% polyvinyl butyral solution, and mix in a pot mill.
The mixture was mixed for 24 hours and then dried at room temperature to provide a test material. This raw material was filled into a carbon mold and sintered at 300 kg/cm ² in nitrogen gas at a temperature of 1600°C to 1900°C. This sintered body was processed into a ring shape, impregnated with a solid lubricant in the same manner as in Example 1, and subjected to a wet sliding test under the following conditions. The results are shown in Table 6. Sliding conditions Test machine Mechanical seal type (ring-on-ring method) Lubrication method Oil lubrication (machine oil) Surface pressure 5Kg/cm ² hours 100 hours

[Table] Example 6 60 parts by weight of metal Si powder with an average particle size of 1 μm, average particle size
To a mixture of 40 parts by weight of 16 μm SiC powder and 1 to 50 parts by weight of graphite powder was added 9 parts by weight of polyethylene wax as a molding aid, and the mixture was heated and kneaded at 150°C. This raw material was molded using a mechanical press at a temperature of 160℃ and a pressure of 1000Kgf/cm ² to form a φ30×
A molded body of φ20×10mm was made. This at 25℃/hour
After heating to 500°C, sintering was performed in stages from 1100 to 1400°C over a long period of time in a nitrogen atmosphere. After polishing the sliding surface of this sintered body, a wet sliding test was conducted under the following conditions. The results are shown in Table 7. Sliding conditions Test machine Mechanical seal type (ring-on-ring method) Lubrication method Oil lubrication (machine oil) Sliding speed 10m/sec Surface pressure 5Kgf/cm ² hours 100 hours

【table】

[Table] From this table, it can be seen that when the amount of solid lubricant added is less than 1% by volume, the coefficient of friction increases and the amount of wear increases. Furthermore, it can be seen that when the amount added exceeds 40% by volume, the friction coefficient does not change, but the amount of wear increases rapidly. Therefore,
The solid lubricant is preferably 1 to 40% by volume. Example 7 (Reference example) 100 g of SiC powder with an average particle size of 1 μm and 2% by weight of BeO added as a sintering aid were sintered using a hot press at 200 Kgf/cm ² at 1800 to 2000°C. After processing it into an outer diameter of 30 mm, an inner diameter of 20 mm, and a thickness of 10 mm, it was impregnated with a solid lubricant using an autoclave and the sliding surface was polished, followed by a wet sliding test under the following conditions. The results are shown in Table 8. Sliding conditions Test machine Mechanical seal type (ring-on-ring method) Lubrication method Oil lubrication (machine oil) Sliding speed 2m/sec Surface pressure 5Kgf/cm ² hours 100 hours

【table】

[Table] From the results, it was found that those impregnated with a solid lubricant had excellent wear resistance. Example 8
(Reference example) Si ₃ N ₄ powder with an average particle size of 0.8 μm and an average particle size of 2 μm
5% by weight each of Y ₂ O ₃ powder and Al ₂ O ₃ powder were added, wet mixed in a pot mill for 24 hours, dried, and molded into a diameter of 50 mm using a mechanical press at a pressure of 1000 Kgf/cm ² . This was sintered in nitrogen for 4 hours at a temperature range of 1600-1800°C. The obtained sintered body has an outer diameter of 30 mm,
After processing the material to have an inner diameter of 20 mm and a thickness of 10 mm and polishing the sliding surface, it was impregnated with solid lubricant using oak crepe, and a wet sliding test was conducted under the following conditions. The results are shown in Table 9. Sliding conditions Test machine Ring-on-ring method Lubrication method Oil lubrication (machine oil) Sliding speed 2m/sec Surface pressure 5Kgf/cm ² hours 100 hours

【table】

[Table] Example 9 (Reference example) ZrO ₂ powder with an average particle size of 0.9 μm was added to ZrO2 powder with an average particle size of 2 μm.
Y ₂ O ₃ powder, MgO powder, and CaO powder were added in an amount of 3 mol % each, wet-mixed in a pot mill for 24 hours, and then dried to obtain a test material. This was molded into a diameter of 50 mm using a mechanical press at a pressure of 1000 Kgf/cm ² . This molded body was then sintered at a temperature range of 1400 to 1650°C for 4 hours. The obtained sintered body has an outer diameter of 30 mm and an inner diameter of 20 mm.
After processing to a thickness of 10 mm and polishing the sliding surface, oak crepe was used to impregnate a solid lubricant, and a wet sliding test was conducted under the same conditions as in Example 3. The results are shown in Table 10. From this result, it can be seen that those to which a solid lubricant was added have excellent wear resistance.

【table】

[Table] Example 10 (Reference example) 100 g of SiC powder with an average particle size of 1 μm and an average particle size of 2 μm
A mixed powder of 100 g of ZrB ₂ powder was wet-mixed and then dried to obtain a test material. This raw material was sintered using a hot press in nitrogen at 300 kgf/cm ² at a temperature of 1600 to 2000° C. for 2 hours. After processing and polishing the obtained sintered body into an outer diameter of 30 mm, an inner diameter of 20 mm, and a thickness of 10 mm, it was impregnated with a solid lubricant using an autoclave, and a wet sliding test was conducted under the following conditions. Test machine Mechanical seal type (ring-on-ring method) Lubrication method Oil lubrication (machine oil) Sliding speed 2m/sec Surface pressure 5Kgf/cm ² hours 100 hours The results are shown in Table 11. From this, the ZrB ₂ -SiC system has excellent wear resistance and can be used as a conductive sliding material.

【table】

[Table] Example 11 (Reference example) 60 parts by weight of metal Si powder with an average particle size of 1 μm and the average particle size
A mixed powder consisting of 40 parts by weight of 2 μm Si-Al-O-N powder and 1 to 50 parts by weight of a solid lubricant (molybdenum disulfide), 60 parts by weight of metallic Si powder with an average particle size of 1 μm and an average particle size of 0.9 μm. Mixing, molding, and sintering were carried out in the same manner as in Example 6 for two kinds of mixed powders prepared by adding 1 to 50 parts by weight of a solid lubricant (boron nitride) to 40 parts by weight of Al ₂ O ₃ powder. After polishing the sliding surface of the obtained sintered body, a wet sliding test was conducted under the following conditions.
The results are shown in Table 12. Sliding conditions Test machine Mechanical seal type (ring-on-ring method) Lubrication method Oil lubrication (machine oil) Sliding speed 10m/sec Surface pressure 5Kgf/cm ² hours 100 hours

【table】

[Table] From this table, it can be seen that when the amount of solid lubricant added is less than 1% by volume, the coefficient of friction increases and the amount of wear increases. Also, the amount added is 40% by volume.
It can be seen that when the value exceeds , the friction coefficient does not change, but the amount of wear increases rapidly. Therefore, the solid lubricant preferably accounts for 1 to 40% by volume. Example 12 Table 13 shows the results of examining the pore size and abrasion resistance of the product of the present invention obtained in Example 1. Sliding conditions Test machine Mechanical seal type (ring-on-ring method) Lubrication method No lubrication Sliding speed 2m/sec Surface pressure 1.5Kgf/cm ² hours 100 hours

[Table] The results show that the amount of wear increases as the pore size increases, and increases rapidly when the pore size becomes larger than 200 μm. Therefore, the pore diameter in the sintered body is preferably 200 μm or less. Also, the porosity
It can be seen that the amount of wear increases when it reaches 50% by volume. Example 13 Steel is commonly used as the material for gears, and steel gears usually must be lubricated. Plastic gears, which can be used without lubrication, have lower mechanical strength than steel gears, and also have drawbacks in terms of heat resistance and wear resistance. Therefore, it can be used without lubrication, and has heat resistance and
The ceramic member of the present invention is suitable as a gear material having various requirements for excellent mechanical strength. 70g of metal Si with an average particle size of 1μm and an average particle size of 16μm
A mixture of 30 g of SiC was mixed with polyvinyl butyral in a pot mill for 24 hours and dried to obtain a test material. This raw material was molded into a product having a diameter of 200 mm and a thickness of 10 mm using a mechanical press at a molding pressure of 1000 Kgf/cm ² . This was sintered stepwise to 1400°C over a long period of time in nitrogen. The obtained sintered body was subjected to a profile gear cutting method and wrapping to produce gears shown in Table 14, and then impregnated with a solid lubricant using an autoclave.

〔Effect of the invention〕

As explained above, according to the present invention, the coefficient of friction is reduced, the wear of the mating material can be reduced, and the thermal shock resistance is significantly improved. As a result, a sliding material with excellent wear resistance, thermal shock resistance, mechanical strength, and corrosion resistance can be obtained, and is used in various sliding parts such as general mechanical seal rings, chemical seal rings, plungers, bearings, sandblasting nozzles, and tappets. It can be applied as a material.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the total number of revolutions and the wear weight of gears, and FIG. 2 is a sectional view of a welding tip cover to which the product of the present invention is applied. 1... Chip cover, 2... Chip, 3... Welding wire.

Claims (1)

[Scope of Claims] 1. Ceramics for sliding materials, characterized in that 1 to 40 parts by volume of a solid lubricant are present in a composite ceramic of silicon nitride and silicon carbide with a pore size of 200 μm or less. 2 The solid lubricant is graphite, molybdenum disulfide, titanium disulfide, tungsten disulfide, boron nitride, fluororesin, tellurium disulfide, selenium disulfide, barium hydroxide, lead chloride, mica, silver iodide, Claim No. 1, which is at least one selected from the group consisting of talc, borax, kaolin, lead oxide, vermiculite, Fe-Mn-lead phosphate, polyethylene glycol, paraffin wax, and stearic acid compound. Ceramics for sliding materials according to item 1. 3. The ceramic for sliding materials according to claim 1, wherein the composite ceramic of silicon nitride and silicon carbide is a sintered body obtained by nitriding a compact made of metal Si powder and silicon carbide powder. 4. The ceramic for a sliding material according to claim 1, wherein the composite ceramic of silicon nitride and silicon carbide has a pore content of 1 to 47 parts by volume.