Monitoring the delubing and sintering of hard metals by means of mass spectrometry

Hard metals are powder metallurgical products composed of WC and Co. Applications for such materials include cutting tools and wear resistant parts. Optimization of the sintering of hard metals requires an understanding of complex changes in the solid, liquid and gas phase chemistries. In situ information is obtained during the sintering of WC - Co compacts on the lab and near production scales. Mass spectrometry is used to monitor changes in the gas composition as a function of temperature and time. Early in the sintering process, adsorbed moisture is evolved and the milling and pressing agents are removed. Oxide reduction occurs followed by melting of the WC - Co eutectic and liquid phase sintering. This paper summarizes the results obtained for various WC - Co compositions, sintering atmospheres and furnace sizes. It is concluded that mass spectrometry is a useful technique for analytical and industrial application.