PREPARATION AND SOME MECHANICAL-PROPERTIE S OF WC-CO-MOS2 ALLOY BY SPARK SINTERING

1.8 similar to 7.8 mol%MoS2 is added to WC-20 mol%Co of a basic alloy system to develop cemented carbides having the ability of self-lubrica tion, where MoS2 is well known as one of the solid lubricants. The spa rk sintering has been applied to the sintering of these MoS2 containin g carbides. The evaluation of microstructures, the hardness and charpy impact tests are also carried out on the spark sintered compacts. The results obtained from this study are summarized as follows. The condi tions selected as the optimum sintering condition for WC-20Co. are: Th e number of pulse is 3000 for preliminary treatment of powders, and th e resistance sintering temperature and time are 1473 K and 0.6 ks, res pectively, where the decreasing rate of specific resistivity of compac ts is a guide to the determination of the number of pulse, and the mic rostructure, displacement of densification and hardness are guides to the determination of the resistance sintering conditions. These condit ions are also used in the spark sintering process of MoS2 containing c arbides. Only three materials, WC, Co and MoS2, are identified in the compacts which are sintered under the conditions mentioned above. It i s considered that the exposed period of compacts are short (0.6 ks) at the maximum sintering temperature (1473 K) and single or condensed pa rticles of MoS2 are surrounded by WC-Co compacts whose relative densit ies are more than 70% at the thermal decomposition temperature (approx imately 1273 K), which lead to the residue of MoS2 in the sintered com pacts. On the other hand, the hardness and Charpy impact values have a tendency of decreasing with the MoS2 content in carbides. In particul ar, the rate of decrease of these values are larger for the compacts l ow in the content of MoS2.