Densification of TiN-Ni cermets by improving wettability of liquid nickel on TiN grain surface with addition of Mo2C

Abstract

A new fabrication method for full density TiN-base cermets by conventional liquid phase sintering in vacuum has been developed in the present study. Poor wettability of liquid Ni on a TiN grain surface was greatly improved with addition of Mo2C into the TiN-Ni alloys and thus a wetting angle changed from about 90 to nearly 0 degrees. The TiN-Mo2C-Ni compacts were able to be sintered to almost full density by a conventional vacuum sintering without controlling the partial pressure of nitrogen gas. Pore formation and pore growth occurring during the sintering of TiN-Ni compacts was attributed to evolution of nitrogen gas due to thermal dissociation of TiN from an uncovered TiN grain surface being directly exposed to pores. Vanadium carbide (VC) appeared to suppress significantly the growth of TiN grains during liquid phase sintering and to improve greatly the mechanical properties of sintered TiN-Mo2C-Ni compacts. (C) 1999 Elsevier Science Ltd. All rights reserved.