Novel TaC0.8 incorporated WC composites with enhanced mechanical properties by spark plasma sintering

Abstract

The WC-based composites incorporated with different concentrations of TaC0.8 were solidified by using ball milling and spark plasma sintering (SPS). The impact of TaC0.8 content on the densification, phase composition, microstructure and mechanical properties of WC-TaC0.8 composites was evaluated. The major constitutions of WC-TaC0.8 composites were WC matrix, (W1−x, Tax)Cn solid solution and W2C phase. The adequate amounts of TaC0.8 additive had promoter function on the generation of W2C and the densification of WC-based composites through carbon vacancies. The (W1−x, Tax)Cn and W2C phases were uniformly dispersed in the WC matrix, effectively bringing a refinement of WC grains. There were the coherent interface of WC (01̅10)/W2C (101̅0) and semi-coherent interface of (W1−x, Tax)Cn (200)/WC (101̅1) in the WC-7.5 wt%TaC0.8 (WTa7.5) composite. The nearly-full densified WTa7.5 composite (99.3%) rendered the best overall mechanical properties, featuring high hardness of 24.9 GPa and high fracture toughness of 8.3 MPa·m1/2. The high fracture toughness was justified by several factors including highly dense and fine microstructure, coherent and semi-coherent interfaces, and a combination of transgranular and intergranular fracture, as well as crack deflection and crack bridging.