Abrasive wear resistance of SiO2-doped polycrystalline alumina

A range of silica-doped alumina ceramics with addition of 0, 0.5, 1, 5 and 10 wt.% of SiO2 was prepared by hot pressing at 1450 °C. Controlled grain growth was achieved by high temperature annealing of hot pressed specimens at 1600 °C. Resistance against wet abrasive wear was tested using custom-built sample holder on a standard grinder/polisher machine. The wear rates increased with increasing rotation speed and loading force, and with size of alumina grains, and decreased with increasing content of SiO2 addition. The measured wear rates were comparable to those of alumina–SiC nanocomposites with similar alumina matrix grain size, but inferior to pure alumina ceramics with submicrometre microstructure. The wear rates of silica doped specimens increased, similarly to monolithic alumina, with the time of high temperature isothermal treatment, which primarily resulted in the growth of alumina grains. The change of the phase composition (crystallisation of low thermal expansion phase mullite) and resulting change of the stress state of the annealed silica doped specimens had negative impact on both the hardness and wear resistance.