Fundamentals of sintering nanoscaled binderless hardmetals

It could be shown that three main processes during sintering of slightly under-stoichiometric binderless WC hardmetals occur: first, the reduction of surface oxides at 800 °C after which densification starts due to cleaned surfaces and the existence of W in a nascent state; second, the secondary carburisation of WC and W at around 1400 °C; and, third, grain growth and pore annealing at around 1600 °C when a closed porosity exists. By adding Cr3C2 as grain growth inhibitor the secondary carburisation step was lowered to around 1000 °C and a solid solution of (W,Cr)2 instead of pure W2C was formed.