Microstructure and mechanical properties near interface between microarc oxidation coating and Al alloy substrate

The microstructure near the interface between a 2024 Al alloy substrate and a ceramic coating formed by microarc oxidation has been studied using scan ning electron microscopy and energy dispersive spectrometry. Hardness and e lastic modulus on the two sides of the interface were investigated using na noindentation and Vickers microhardness measurement. The results showed tha t the microstructure of the substrate was not changed by application of the coating, and a hardened zone was not observed. During microarc oxidation, no remelting of the substrate occurred, but remelting of the alumina cerami c coating on the other side of the interface did take place. The mechanical properties on the two sines of the interface had obvious differences: in a certain range of coating thickness there was a gradual increase of hardnes s and elastic modulus from the interface to the interior of the coating, bu t hardness remained almost constant in the substrate.