Analysis of friction and wear performance of Y${}_2$O${}_3$-doped Si${}_3$N${}_4$ ceramic using the estimation of stress

A variety of combinations of Y${}_2$O${}_3$ and Al${}_2$O${}_3$ were used as sintering aids in the fabrication of Si${}_3$N${}_4$ ceramics via gas pressure sintering (GPS). Based on the prediction of the residual thermal stress at the interface, the influence of crystal phases on the wear properties of Si${}_3$N${}_4$ ceramics was analyzed. As a result, with the increase of Y${}_2$O${}_3$ addition from 1 to 9 wt%, there are four kinds of crystal phases being firmly discovered in the sample, Y${}_2$Si${}_2$O${}_7$, YSiO${}_2$N, Y${}_4$Si${}_2$O${}_7$N${}_2$, and Y${}_2$Si${}_3$O${}_3$N${}_4$. The crystal phases of Y${}_2$Si${}_2$O${}_7$, YSiO${}_2$N, and Y${}_4$Si${}_2$O${}_7$N${}_2$ inhibit the particle flaking during the friction process, which greatly inhibited the progress of the abrasive wear, and optimize the wear resistance of silicon nitride ceramics. According to Selsing's model, it can be predicted that the interface residual thermal stress caused by the intergranular phase Y${}_2$Si${}_3$O${}_3$N${}_4$ is 22-35% higher than that caused by the other three intergranular phases. The crystal phase Y${}_2$Si${}_3$O${}_3$N${}_4$ intensifies the shedding of grains during wear, and reduces the wear performance of silicon nitride ceramics. In addition, the silicon nitride ceramics with 5wt% Y${}_2$O${}_3$ show better wear resistance, and the wear rate is 1.8 × 10${}^{-6}$ mm${}^3$ N${}^{-1}$ m${}^{-1}$.