窒素を含む炭化チタン基サーメットに観察される白点の生成機構

概要

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It has been known that white spots frequently appear in SEM structure of titanium carbide (TiC) grains in nitrogen contained TiC based cermets. The formation of the white spots was studied as functions of alloy system, alloy composition and sintering conditions, using specimens having coarse TiC grains in the structure.It was found that the white spots appeared only in TiC-TiN (or Ti(C, N))-Mo2C-Ni alloy system, and the formation of white spots varied according to the above factors. It was assumed in TiC-TiN-Mo2C-Ni alloy system that TiC grains did not easily dissolve in liquid binder at the sintering temperature, because molybdenum atoms tended to diffuse in TiC grains to form TiC-Mo2C solid solution. Consequently, TiC grains had to dissolve with making many slits around the periphery of TiC grain, resulting in the liquid-infiltration in the slits and the formation of white spots.