Abstract
Strengthening phenomena of hot-isostatic alloy pressed WC-10%Co alloy (H.I.P. alloy) were investigated mainly by means of direct observation of the defect structures (appearing in the so-called white spot on fracture-surface), which are thought to have acted as the origin of fracture, and by comparing with the results of normally vacuum-sintered alloy (N.S. alloy). Results obtained were as follows:
(1) Slight changes in the mean grain size of WC, the composition and distribution of the binder phase, etc., were observed in H.I.P. alloy. But these changes were considered to have no relation to the strength-increase in H.I.P. alloy.
(2) It was made clear that the strengthening mechanism of H.I.P. alloy was directly related to the disappearance of a small number of large pores (which usually exist in N.S. alloy). However, it was shown here that a sharp increase in strength was not always visualized due to H.I.P., because it was usual that some large WC grains were contained in the structure.
(3) The strength level which would be obtained in H.I.P. alloy was suggested to be comparable to the level obtainable in N.S. alloy.
