Dry sliding wear of MAO-coated A356/20 vol.% SiCp composites in the temperature range 25–180 °C

Thick alumina coatings were performed on A356/20 vol.% SiCp composites by micro-arc oxidation (MAO) process with different processing time. MAO-coated layer is composed of α-alumina, γ-alumina and mullite, and the hardness value increases and then decreases sharply with distance from the interface. The dry sliding wear tests were performed on A356/20 vol.% SiCp composites with and without surface coating. The samples were tested by pin-on-disc wear test equipment with different applied load and sliding velocity in a temperature range 25–180 °C. On the basis of the observations and analysis of the worn surface, worn subsurface, wear debris and variation of friction coefficient, the role of MAO coating layer is examined. It is revealed that MAO coating improves resistance to wear of A356/20 vol.% SiCp composites. The coated and uncoated specimens show similar results in wear rate for the mild wear regions, whereas the coated specimen show much better resistance to wear in the severe wear conditions for A356/SiCp composites by retarding the transition of the mild-severe wear of the materials.