Characteristics and origin of clusters in submicron WC-Co cermets

Abstract

The microstructure of the WC phase in submicron WC-Co alloys has been investigated by transmission electron microscopy. The existence of clusters formed by several grains mainly related by Σ =1 and Σ=2 high-coincidence orientation relationships is shown. The features of these grain boundaries are studied using high-resolution electron microscopy. Two cases of Σ =1 orientation are investigated. In one case, the boundary contrast arises from the presence at the interface of a nanometric intermediate layer. In the other case, a grain boundary separating domains with different carbon positions is evidenced. Investigations of the starting WC powder indicate the existence of clusters already in particles and reveal the polygonal shape of WC grains before sintering. Some microstructure characteristics of the clusters suggest that the majority of clusters observed in the sintered material arise from the powder.