Abstract
The sintered WC compact was machined by electric discharge machining, and then annealed in vacuum at 800-1300°C for the time up to 80hrs. The phase change of different phases (β-WC1-x, W2C) appearing along the machining surface was studied as functions of annealing temperature and time. It was found that the different phases had a tendency to disappear and finally change to WC. Such a phase change could be explained by assuming that two sorts of eutectoid reactions, that is, β-WC1-xW2C+WC and W2CW+WC took place during annealing, and that the formed W2C or W changed to WC, because they reacted with the free carbon remaining in non-equilibrium state in the surface layer. Microstructural changes of surface layer due to annealing were in detail studied.
