In situ reactive synthesis and plasma-activated sintering of binderless WC ceramics

Binderless micrometre tungsten carbide ceramics (similar to 1.1 mu m) were in situ synthesised and densified by plasma-activated sintering (PAS) from mixed powders of tungsten trioxide and carbon black. The influence of sintering process and powders' composition ratio on the phase composition, microstructure and mechanical properties of as-prepared samples was clarified in detail. The phase evolution was ascertained by X-ray diffraction to be WO3 -> WO2.72 -> WO2 -> W2C -> WC, with the formation of CO and CO2 gases. The sample with nearly single WC phase, dense structure and excellent mechanical properties was fabricated under the optimised process with the proper composition ratio. Owing to the micrograin size, the fracture toughness (8.88 MPa m(1/2)) was enhanced while high hardness (2159 HV 10) was maintained, in the absence of any ceramic toughening phase.