Mechanical and Tribological Behaviors of Hot-Pressed SiC/SiCw-Y2O3 Ceramics with Different Y2O3 Contents

Sintering additives are commonly used to reduce the conditions required for densification in composite ceramics without compromising their performances simultaneously. Herein, SiC/SiCw-Y2O3 composite ceramics with 10 vol.% SiC whiskers (SiCw) and different Y2O3 contents (0, 2.5, 5, 7.5, and 10 vol.%) were fabricated by hot-pressed sintering at 1800 °C, and the effects of Y2O3 content on the microstructure, mechanical properties, and tribological behaviors were investigated. It was found that the increased Y2O3 content can promote the densification of SiC/SiCw-Y2O3 composite ceramics, as evidenced by compact microstructure and increased relative density. The Vickers hardness, fracture toughness, and flexural strength also increased when Y2O3 content increased from 2.5 vol.% to 7.5 vol.%. However, excessive Y2O3 (10 vol.%) aggregated around SiC and SiCw weakens its positive effect. Furthermore, the Y2O3 additive also reduces the coefficient of friction (COF) of SiC/SiCw-Y2O3 composite ceramics, the higher the Y2O3 content, the lower the COF. The wear resistance of SiC/SiCw-Y2O3 composite ceramics is strongly affected by their microstructure and mechanical properties, and as-sintered SiC ceramic with 7.5 vol.% Y2O3 (Y075) shows the optimal wear resistance. The relative density, Vickers hardness, fracture toughness, and flexural strength of Y075 are 97.0%, 21.6 GPa, 7.7 MPa · m1/2, and 573.2 MPa, respectively, the specific wear rate of Y075 is 11.8% of that for its competitor with 2.5 vol.% Y2O3.