Optimizing densification and mechanical properties of spark plasma sintered ZrB2-SiC ceramic composites

This study investigates the impact of different powder milling methods on the densification and mechanical properties of ZrB 2 -SiC ceramic composites processed via spark plasma sintering (SPS). Powders were prepared using two ball milling techniques: tungsten carbide (WC) and conventional ZrO 2 . The densification behavior during SPS was monitored, and the sintered samples were evaluated for their relative density, hardness, fracture toughness, and flexural strength. Results show that WC milling significantly enhances densification, achieving 99.2 % relative density at 2100 °C/65 MPa/15 min, compared to 96.5 % for ZrO 2 -milled samples. This improvement is due to WC's sintering aid effect, which promotes grain boundary diffusion and particle packing. However, ZrO 2 -milled composites exhibit superior hardness (17.38 GPa) and fracture toughness (3.97 MPa m 1 / 2 ), attributed to their refined grain structure and the absence of softer ZrO 2 phases. Conversely, WC-milled samples show slightly higher flexural strength (384–516 MPa), likely due to the transformation toughening effect of the secondary ZrO 2 phase. Overall, WC milling improves densification and flexural strength, while ZrO 2 milling yields finer-grained composites with higher hardness and toughness, making it better suited for wear-resistant and mechanically demanding applications.