Effect of TiO2 and ZrO2 reinforcements on properties of Al2O3 coatings fabricated by thermal flame spraying

The alumina composite coatings reinforced with 25% ZrO2 (denoted as AZ-25) and 3% TiO2 (denoted as AT-3) were deposited on low carbon steel using a thermal flame spraying. The microstructure, phase composition, microhardness and tribological properties of the coatings were investigated. The XRD results of the coatings reinforced by TiO2 (AT-3) revealed the presence of α-Al2O3 phase as matrix and new metastable phases of γ-Al2O3 and κ-Al2O3. However, the coatings reinforced by ZrO2 (AZ-25) consist of α-Al2O3 as matrix, q-ZrO2 and m-ZrO2. In most studied conditions, the AT-3 coating displays a better tribological performance, i.e., lower coefficient of frictions and wear rates, than the AZ-25 coating. It was also found that the microhardness of the coatings was decreased with the reinforcement of ZrO2 and increased with TiO2.