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AssigneeSumitomo Electric Industries, Ltd.
InventorsMasamichi Yamagiwa, Akira Yamakawa, Takao Nishioka, Takashi Matsuura
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A silicon nitride ceramic sliding member which includes Si.sub.3 N.sub.4 grains as a main component and is shaped or controlled in dimensions through hot plastic working wherein the Si.sub.3 N.sub.4 particles mainly includes .beta.-type columnar crystal grains. The ceramic sliding member is produced by the step (I) of preparing a preform made of silicon nitride ceramic sintered body including Si.sub.3 N.sub.4 grains as a main component wherein the average grain size (average grain size in minor axis in the case of .beta.-type columnar crystal grains) of the Si.sub.3 N.sub.4 grains is at most 0.5 .mu.m, and the hot plastic working step (II) of placing the preform in a mold and effecting hot plastic deformation of the preform for shaping or dimensional control thereof while simultaneously increasing the average aspect ratio of the .beta.-type columnar crystal grains. The resultant sliding member has excellent sliding properties, a high mechanical strength and a high reliability at a low cost without resort to grinding or the like for shaping thereof.
A process for producing a silicon nitride ceramic sliding member with improved mechanical strength, comprising the step (I) of preparing a preform substantially free of free silicon and made of silicon nitride sintered body comprising as main components, at least one member of the group consisting of a .alpha.-Si.sub.3 N.sub.4 grains having an average grain size of up to 0.5 .mu.m and .beta.-Si.sub.3 N.sub.4 grains having an average grain size of up to 0.5 .mu.m in minor axis and a hot plastic working step (II) by placing said preform in a mold and effecting hot plastic deformation of said preform for shaping or dimensional control thereof while simultaneously increasing an average aspect ratio of S.beta.-columnar crystal grains of the silicon nitride sintered body whereby the proportion of .beta.-columnar crystal grains of the resultant plastic work product is at least 70% of the Si.sub.3 N.sub.4 grains.
Dependencies are inferred from the claim text.