Synthesis and microstructure evolution of WCoB based cermets during spark plasma sintering

WCoB based cermets were prepared by spark plasma sintering at sintering temperature among 600 degrees C-1200 degrees C. The phase evolution was investigated by detecting density behavior, phase composition, microstructure and mechanical properties during sintering process. The sintering process can be divided into three stages: powder densification, solid phase reaction and liquid phase sintering. WCoB hard phase forms at 1000 degrees C during solid phase sintering, showing better mechanical properties than Co2B, especially on Vicker's hardness. WCoB hard phase forms on the basis of Co2B binary boride and its content increases in liquid phase sintering stage with high density. The Vicker's hardness and transverse rupture strength (TRS) reach the maximum value of 1262 Hv and 1212 MPa at 1200 degrees C and 1170 degrees C, respectively. The fracture toughness reaches the maximum value of 21.8 MPa m(1/2) at 1050 degrees C, and the inter-granular fracture is the main fracture mechanism.