Effect of surface macroroughness on the microstructure and sliding wear properties of Al2O3+13 wt.% TiO2 thick coatings

Two macro-roughness patterns namely spiral grooving and diamond knurling were performed on an AISI/SAE 1045 cylindrical steel bar. Al2O3 + 13 wt.-% TiO2 powder was deposited by utilizing a multi-pass torch. Microstructure, microhardness and wear resistance were analyzed. The presence of both gamma-Al2O3 and alpha-Al2O3 throughout the coating was promoted by partially melted and un-melted particles; however, the formation of interlayers of hard alpha-Al2O3 was influenced by the re-heating during the multi-pass torch causing transformation from gamma-Al2O3 ->alpha-Al2O3. Knurling pattern specimens contained less defects owe to a suitable splat accommodation thus strengthening the inter-splat anchorage. The improved sliding wear resistance was influenced by both the combination of gamma-Al2O3 (toughness) and alpha-Al2O3 (hardness) phases and, predominantly by the reduced porosity and micro-cracks in specimens with the knurling pattern.