1. Field of the Invention
This invention relates to a ceramic sliding member and a method of manufacturing the same.
2. Description of the Prior Art
Sintered silicon carbide material, sintered silicon nitride material and the like are expected as ceramics for forming a sliding member. However, the sintered silicon carbide material is inferior in fracture toughness and strength though superior in anti-seizing property, and accordingly, the component formed of the sintered silicon carbide material is disadvantageous in that it is apt to crack or fracture while it is processed, is incorporated or is in operation. On the other hand, the sintered silicon nitride material is superior in resistance to heat, resistance to heat shock, mechanical strength and resistance to corrosion, and accordingly, it has been expected as the material for forming various mechanical parts which operate under severe conditions under which metal parts cannot be used.
Since Si.sub.3 N.sub.4 cannot be in liquid phase, an auxiliary for firmly binding particles is required when sintering silicon nitride material. As the auxiliary, there has been wide used an oxide which melts and forms a liquid phase or combines with other components to form a low-melting compound. Typically, the auxiliary is Y.sub.2 O.sub.3, Al.sub.2 O.sub.3 or BoO. The properties of sintered silicon nitride material depends not only on the properties of Si.sub.3 N.sub.4 but also on the properties of the auxiliary which forms the grain boundaries in the sintered silicon nitride material. There has been well known a sintered silicon nitride material which is formed by adding about 10 wt % Y.sub.2 O.sub.3, Al.sub.2 O.sub.3 or the like to Si.sub.3 N.sub.4 (the major component) and sintering the mixture in an inert gas atmosphere. However, the conventional sintered silicon nitride material cannot be free from the problems inherent to sintered materials, e.g., lack of reliability such as defect due to foreign particles, pores or the like, or lack of the absolute strength.
In Japanese Unexamined Patent Publication No. 61-68373, there is disclosed a sintered silicon nitride material which is obtained by adding a predetermined amount of Y.sub.2 O.sub.3, MgO and CeO.sub.2 to Si.sub.3 N.sub.4 and sintering the mixture.
Such a sintered silicon nitride material which is sintered using Y.sub.2 O.sub.3, MgO and CeO.sub.2 as the auxiliary is high in strength and superior in resistance to impact. However sliding tests in which chrome-plated material was used as the mate material have revealed that the sintered silicon nitride material is slightly inferior in resistance to wear and in anti-seizing property.