Influence of nano-sized La2O3 addition on the sintering behavior and mechanical properties of WC–La2O3 composites

Abstract This work explores the addition effect of nano-sized La 2 O 3 powder (0–7 wt%) on the sintering behavior, microstructure and mechanical properties of WC–La 2 O 3 composites prepared by spark plasma sintering at 1600 °C under a uniaxial pressure of 50 MPa. The results indicated that when the content of La 2 O 3 increased from 0 to 7 wt%, both the onset and termination temperatures for sample densification were delayed. The onset temperature increased from 850 to 975 °C and the termination temperature raised from 1400 to 1600 °C, respectively. The relative density of the samples raised from 96% (for pure WC) to 97.5% (for the composites with 3–7 wt% La 2 O 3 ). The added La 2 O 3 could suppress the growth of WC grains and inhibit the formation of triangle prism shaped WC grains. However, with more La 2 O 3 (more than 5 wt% in this work), the agglomeration of La 2 O 3 became serious. With the increase in La 2 O 3 content, the Vickers hardness and flexural strength of the samples initially increased and then decreased, reaching the maximum of 2100 HV 10 with 3 wt% La 2 O 3 and 1300 MPa with 1 wt% La 2 O 3 , respectively. However, the Palmqvist indentation fracture toughness gradually decreased from 7.5 to 5.5 MPa m 1/2 when the content of La 2 O 3 increased from 0 to 7 wt%.