Influence of Defects in Surface Layer of Al2O3/TiC and SiAlON Ceramics on Physical and Mechanical Characteristics

The paper studies the influence of diamond grinding, lapping, and polishing on the surface layer and defectiveness of the Al2O3/TiC and SiAlON ceramic samples. The index of defectiveness ID, which is the product of the defect density and the defective layer’s thickness (Rt), and a method for its evaluation are proposed to quantify the defectiveness of the ceramic surfaces. Lapping reduces the Rt parameter by 2.6–2.7 times when the density of defects was decreased by 2 times. After polishing, the Rt parameter decreases to 0.42 μm for Al2O3/TiC and 0.37 μm for SiAlON samples. The density of defects decreases many times after polishing: up to 0.005 and 0.004, respectively. The crack resistance of the polished samples increased by 5–7%. The volumetric wear of polished samples decreased by 1.5–1.9 times compared to the ground ones after 20 min of abrasion wear. The polished samples show a decrease in the coefficient of friction at 800 °C and a decrease in the volumetric wear by 1.5 and 1.3 times, respectively, compared to the ground ones after 200 m of friction distance. The volumetric wear at high-temperature friction of sliding for polished specimens was 55% and 42% less than for the ground ones, respectively.