Abstract
In order to clarify the sturctures and the properties of binder phase in cemented tungsten carbide alloy with cobalt, physical properties such as lattice constant, Curie temperature and magnetization of γ-Co solid solution containing up to 15% WC by weight have been studied. Based on these results, the change of the binder phase in WC-5.5% Co composition during the sintering has been first observed. Then, the effect of the various cooling rate from melt on the kinds of alloy phases, and also the structue of γ-Co phase of the Co rich-WC alloys have been investigatd by the method of microscope, X-ray diffraction and thermomagnetic techniques. The results obtained were as follows. By slow cooling, ry or (γ+WC) phases, and by rapid cooling (γ+η) phases appeared on the samples of 5-35% WC-Co alloys. But (γ+η) phases were unstable, and so by annealing, (γ+η) phase changed to stable (γ+WC) phase. These results mentioned above could be described consistently by the double phase diagram containg unstable η phase shown in Fig.8. The process of decomposition of η phase and the simultaneous change of γ phase were also invetigated.
