Microstructure and mechanical properties of (Ti,W,Ta)C-xMo-Ni cermets

(Ti,W,Ta)C-xMo-20Ni (x =0-20 wt.%) system cermets were prepared by using (Ti,W,Ta)C solid solution as hard phase, without adding secondary carbides in this work. The microstructures exhibited two kinds of carbide grains observable in the BSE mode: one had a dark core-gray rim structure: the other had a dark core-white inner rim-gray outer rim structure. Several (Ti,W)C white particles with high W content were also observed in the microstructures. Results showed that molybdenum has completely dissolved in the Ni binder and mainly was found in the rims of the carbide particles. As the Mo content increased, the wettability between (Ti,W,Ta)C particles and metallic phase was improved, and the shrinkage of cermets increased, the porosity decreased. Results also revealed that finer microstructures were obtained with the increase of Mo addition. But excess Mo addition caused the aggregation of particles. Mechanical properties such as hardness and TRS improved with the increase of Mo content, but the TRS of cermets reached a peak value at the 15 wt.% Mo addition, then declined with the further increase of Mo addition. (C) 2011 Elsevier Ltd. All rights reserved.