Preparation and Some Mechanical Properties of WC-Co-MoS<SUB>2</SUB> Alloy by Spark Sintering

1.8∼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-lubrication, where MoS2 is well known as one of the solid lubricants. The spark sintering has been applied to the sintering of these MoS2 containing 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 conditions selected as the optimum sintering condition for WC-20Co. are: The number of pulse is 3000 for preliminary treatment of powders, and the resistance sintering temperature and time are 1473 K and 0.6 ks, respectively, where the decreasing rate of specific resistivity of compacts is a guide to the determination of the number of pulse, and the microstructure, displacement of densification and hardness are guides to the determination of the resistance sintering conditions. These conditions are also used in the spark sintering process of MoS2 containing carbides. Only three materials, WC, Co and MoS2, are identified in the compacts which are sintered under the conditions mentioned above. It is considered that the exposed period of compacts are short (0.6 ks) at the maximum sintering temperature (1473 K) and single or condensed particles of MoS2 are surrounded by WC-Co compacts whose relative densities are more than 70% at the thermal decomposition temperature (approximately 1273 K), which lead to the residue of MoS2 in the sintered compacts. On the other hand, the hardness and Charpy impact values have a tendency of decreasing with the MoS2 content in carbides. In particular, the rate of decrease of these values are larger for the compacts low in the content of MoS2.