Wear resistance of SiO₂-doped Y-TZP grinding media during wet milling

Grinding media 1 mm in diameter, containing 0.4 and 0.7 wt% SiO ₂, were fabricated using Y-TZP powder prepared by the liquid-phase method. The wear resistance of media for grinding, with and without the addition of BaTiO₃ powder, was evaluated at 20-80°C in water and in a nonaqueous solvent, isoparaffin. A rapid increase in the media wear rate of SiO₂-undoped media at 60°C was observed using water as a solvent, but little wear was observed for isoparaffin. The operating time until a rapid increase in the wear rate was observed in water increased with the increase in the grain size of the Y-TZP media. When the media wear became stable, the media surface was observed to be smooth. This suggested that the hydration reaction of Y₂O₃ and/or ZrO₂ by OH^- was inhibited by an increase in the grain size, and as a consequence, the decay of the grain boundaries was suppressed. In contrast, several traces of grain loss from the grain boundaries were confirmed on the worn surface of the media when a rapid increase in the wear rate was observed. The wear resistance for grinding BaTiO₃ powder using SiO₂-doped and -undoped media was also investigated. The wear for SiO₂-undoped media increased drastically with increasing slurry temperature; however, the wear for SiO₂-doped media did not increase, but was low and stable, regardless of the slurry temperature. This indicated that the hydration reaction of Y₂O ₃ and/or ZrO₂ by OH^- was further inhibited by the segregation of SiO₂ at the grain boundaries, and hence SiO ₂-doped Y-TZP media have high wear resistance, even with increased slurry temperature.