This study reports the improvement in microstructural and tribological characteristics of sintered alumina (Al2O3) ceramic subjected to ultrasonic nanocrystalline surface modification (UNSM) technique. The surface microstructure of the untreated and UNSM-treated specimens was examined by scanning electron microscopy (SEM), laser scanning microscopy (LSM) and X-ray diffraction (XRD). The tribological properties of the specimens were assessed using a ball-on-disk tribometer against a bearing steel (SAE52100) ball. It was confirmed by SEM that the UNSM-treated specimen had much denser microstructure than that of the untreated specimen. The surface roughness of the UNSM-treated specimen obtained by AFM was found to be smoother compared to that of the untreated specimen, which may be attributed to the decrease in porosity. The tribological test results showed that the UNSM-treated specimens exhibited better tribological properties compared to those of the untreated specimens. It was also found that the UNSM technique was able to modify the surface in the topmost surface layer. The results of this study are expected to make sintered Al2O3 ceramic more attractive for a numerous applications in various industries.

Keywords: Alumina, Friction, Wear, Surface engineering.