Abstract
This investigation was undertaken to clarify the mechanism of micropore-formation in WC-Co alloys, from the viewpoint that pores would be resulted from coarse Co particles which pre-existed in (WC+Co) mixture. High carbon two-phase WC-Co alloys with about 10 and 20% Co were in vacuum sintered under various conditions, using usually ball-milled mixtures in which some amounts of coarse Co particles were intermixed for a model-experiment, or from which pre-existed coarse Co particles were removed or not.
Results obtained were as follows:1) In case of the low temperature sintering including solid-phase sintering, coarse Co particles in the mixture became Co pools and changed into pores as sintering time increased. In case of the high temperature sintering, those Co pools tended to change rapidly in pores, when the Co content in the alloy was low. 2) Thus, the structural defects such as Co pools and pores were confirmed to be closely related to each other. Pores above mentioned didn't develope in the alloys, for instance, with high Co contents because of the facility of viscous flow of the matrix. 3) The above results in model-experiments were considered to be available also in the usual WC-10% Co alloy. Because, the removal of coarse Co particles which pre-existed in the ball-milled mixture resulted in disappearence of the pores, the dimensions of which corresponded to those of removed Co particles, leading to a sharp increase in the strength of alloys.
