Microstructure and dry sliding wear behaviour of titania and alumina-titania coatings

The microstructure, hardness and wear properties of atmospheric plasma spray coating of TiO2 and Al2O3-13TiO(2) with incremental hydrogen fractions (11.1-23.8%) in primary gas have been investigated in this work. TiO2 coating shows a fine bead-like surface structure, while Al2O3-13TiO(2) predominantly exhibits a splat-like morphology. The microstructure shows a slight refinement in the structure for the highest hydrogen content possibly due to the higher specific enthalpy of the plasma plume. Both coatings show the highest hardness for samples coated with the highest hydrogen content possibly due to the refined structure. The roughness shows a mild decreasing trend for TiO2 coating, while the reverse trend is observed for Al2O3-13TiO(2) coating. The wear loss and friction coefficient show a flat trend (0.4-0.6) for all the hydrogen contents. The worn tracks show a compacted mixture of ceramic, graphite and metallic particles.