Ceramic Coatings on TC4 Titanium Alloy Deposited by AC Microarc Oxidation

An oxide coating on TC4 Titanium alloy was prepared in an aluminate solution by the alternating-current microarc oxidation (MAO) method. The microardness (H) and elastic modulus (E) of the MAO ceramic coating were determined by the mechanical properties microprobe. The influence of microarc discharge on microstructure and properties of the coating and alloy substrate were discussed. The microarc discharge process has hardly influence on the microstructure of the alloy substrate. No oxygen atoms from the solution diffuse into the unoxidized titanium substrate. The hardness and elastic modulus profiles of the MAO coating are similar. From the coating surface to the interior of the coating, H and E gradually increase. H and E can reach maximum values of 13GPa and 230GPa respectively in the coating near the interface. The changes in relative contents of Ti O2 rutile and TiAl2O5 spinel along the coating thickness determine H and E profiles in the coating.