Effects of TiC Powder Characteristics and Sintering Temperature on the Microstructure and Mechanical Properties of TiC-20Mo-10Ni Cermets

TiC-Mo-Ni cermets were prepared by vacuum sintering using Ni powder as well as the self-synthesized ultrafine TiC and Mo powders as raw materials. Ni used as sintering additive was added to activate the sintering process. The effects of TiC grain size and sintering temperature on mechanical properties and microstructure of TiC-Mo-Ni cermets were investigated. The results showed that Mo was dissolved into TiC phase to generate (Ti, Mo)C solid solution and form a typical core-rim structure. The grain size of cermets was greatly affected by the particle size of raw material TiC powders. In addition, the increases of oxygen content and grain size in TiC powder were detrimental to the densification of TiC-Mo-Ni cermets. By using the TiC powder obtained under the calcium treatment temperature of 1523 K, the TiC-20Mo-10Ni cermet sintered at 1773 K in vacuum had a high relative density (98.8 pct), uniform microstructure, fine grain size (1.49 mu m) and excellent mechanical properties (with the Vickers hardness, fracture toughness, transverse rupture strength of 2081 HV30, 11.43 MPa center dot m1/2 and 813 MPa, respectively). Moreover, the increase of TiC grain size led to the transition of fracture mechanism from intergranular fracture to transgranular fracture, which was favorable for the improvement of toughness.