Micro-mechanical properties of ceramic coating fabricated by plasma electrolytic oxidation on hot-dip aluminized steel

Micro-mechanical properties such as nanohardness, elastic modulus, fracture toughness, etc., of a composite coating on hot-dip aluminized steel, which consists of Al2O3 layer, Al layer and FeAl layer, were evaluated by using nanoindentation method. The morphologies of nanoindentation were observed using SEM. There are some pores with micron scale or sub-micron scale within ceramic coating formed by plasma electrolytic oxidation, and the effects of pores on load-displacement response and crack propagation were analyzed. The results show that elastic modulus and hardness of ceramic coating are about 226.4 GPa, 19.6 GPa, respectively. Mechanical properties of ceramic coating are very discrete when the nanoindentation depth is 250 nm. The propagation resistance of crack in Al2O3 layer is larger than that in FeAl layer. Radial crack emerges from the corner of residual impression of FeAl layer and propagates along straight line. For ceramic layer in addition to radial crack, lateral crack also appears in nanoindentation.