The reason why WC powder of good quality cannot be obtained by the process of heating the WO3 and C mixture in H2 was examined by simple experiments. The authors obtained the following conclusions so that the 2 stage-carburization was adequate to solve the problem.
1) The reduction by H2 occurs preferentially to the reduction by C when the mixture of WO3 and C is heated in H2.
2) The H2O formed by the reaction of WO3+H2 reacted with carbon at the reacting zone. The quantity of the H2O depends upon both the way of charging and heating conditions, affecting the carbon content of WC.
3) WC crystals of abnormal shape were found when the coarse WO3 powder was used. The reason was discussed.
4) The WC powder of good quality was obtained when the H2O was either completely removed or not formed and when fine WO3 powder was used.