The Microstructural Change near the Surface of Ti(C, N)-Mo₂C-Ni Sintered Compacts

Abstract

The anomalous structures appearing near the specimen surface were studied for Ti(C, N)-Mo₂C-Ni alloys prepared by vacuum-sintering.
It was found that surrounding structures of carbonitride particles were not observed in the surface layer (such a layer is named "surrounding structure free layer, SSFL"), and that the formation of SSFL was related to the nitrogen loss from specimen surface during sintering. The thickness increase of SSFL was restrained with the increase of sintering time, in contrast to a previous result reported by the authors on the f free layer in nitrogen contained WC-β-Co alloys. This phenomenon would be understood, considering the following fact being peculiar to this alloy system, that the solutes concentration gradient near the surface layer decreases with increasing thickness of SSFL. In addition, changes in hardness, lattice parameter of hard phases, etc., near the surface layer were discussed.