Effect of sintering atmosphere on microwave prepared WC–8wt.%Co cemented carbide

•WC–8wt.%Co green compacts were fabricated using microwave sintering under different atmospheres (N2, Ar, N2 + H2 and CH4).•Layer-structure formed accompanied with decarburization on the sample surface in N2 and N2 + H2 atmosphere.•A small quantity of CH4 could lead to serious carburization.•The formation mechanism of layer-structure was discussed.•The heating property of N2 and Ar under microwave exposure was discussed.

Microwave sintering has emerged in recent years as a new method for preparing cemented carbides. To investigate the effect of sintering atmospheres on cemented carbides, WC–8wt.%Co green compacts were sintered using microwave sintering technique under different atmospheres. The results showed that the layer-like structure is formed accompanied with decarburization on the sample surface in N2 and N2 + H2 atmosphere. This layer-structure became more complicated in N2 + H2 than in pure N2 atmosphere. On the contrary, we found that a small amount of CH4 (one percent in volume) could lead to serious carburization. Then, the formation mechanism of layer-structure was discussed. In addition, Ar atmosphere had little effect on the microstructure. However, the problem of thermal instability and temperature runaway was more severe in Ar than in N2 atmosphere.