Effect of Ball Milling Time on Microstructure and Properties of MoCoB Cermet

Molybdenum powder, cobalt powder and boron powder were mixed by ball-milling for different times (1, 12, 24, 36, 48 h). MoCoB cermet was prepared by vacuum liquid phase sintering with the mixed powder. The effects of the ball milling time on phase composition, microstructure, hardness and corrosion resistance of MoCoB cermet were investigated. The results show that MoCoB cermets obtained under different ball milling times were all mainly composed of MoCoB metal compound phase and cobalt metal phase. With the extension of ball milling time, the raw materials were mixed more uniformly, and the reactions were more thorough during sintering, therefore the content of MoCoB phase increased in the cermet. The extension of ball milling time provided more nucleation points for the formation of MoCoB phase and enhanced the fluidity of liquid phase during sintering, resulting in the decrease of grain size and porosity. With increasing ball milling time, the hardness of the cermet increased; the self-corrosion potential increased, and the self-corrosion current density decreased, indicating the improvement of the corrosion resistance.