Tribological Behavior of Alumina Ceramics With Nano-TiO2 as a Sintering Aid in Non-Conformal Contact

Abstract

The study emphasized the sintering behavior and tribo-mechanical properties of alumina ceramics by nano-TiO2 addition as a sintering aid. With increase in sintering temperature, the bulk density of alumina has increased gradually and optimized at 1600 °C. The optimizing effect of densification at 1600 °C is 98.25% by the addition of 1 wt% nano-TiO2. The maximum solid solubility of titania in alumina grains was at 1600 °C and causes optimization of densification by addition of 1 wt%. The excess addition of TiO2 formed low dense Al2TiO5, appearing as a secondary phase at grain boundaries and does not significantly improve densification. Fracture toughness increases and coefficient of friction decreases with the addition of nano-TiO2 in alumina matrix. The addition of 1 wt% nano-TiO2 improved hardness to 8.82% and reduces specific wear-rate to 45.56%. The addition of 1 wt% nano-TiO2 greatly influenced the microstructure of sintered Al2O3. The morphology was sharply changed from hexagonal columnar shape to order sub round orientation which also directly impact the tribo-mechanical properties of sintered alumina. The addition of 1 wt% substantially decreases wear track depth as observed by a 3D surface profilometer. Microscopic observation of the worn-out surface showed that wearing is majorly caused by plastic deformation and abrasion.