The factors leading to abnormal grain growth during sintering of hard alloy

Abstract

This work investigated the sintering of the nanocrystalline tungsten carbide and cobalt composite powder. Vacuum sintering and spark plasma sintering (SPS) were used to consolidate powders into bulk nanocrystalline materials. In addition, two methods of the cobalt introduction were developed for making WC/Co compositions. The first one uses mechanical mixing in ball milling machine. The second one is based on a precipitation and reduction of the cobalt salt on the WC particle surface. The oxygen was always present in the produced powders. Therefore, a control of common carbon is necessary to produce bulk materials with correct chemistry. When vacuum sintering or SPS process are used for consolidation, the addition of grain growth inhibitor is necessary to minimize grain growth. Sintering hard alloys using the nanocrystalline WC-Co composite powders has unique properties and potential for commercial applications.