Characterization of Al2Ti/Al3Ti-based intermetallic and Al2O3/TiO2-based oxide composite coatings fabricated on Ti6Al4V alloy

In this work, an aerospace-grade Ti6Al4V alloy was coated by electro spark deposition (ESD), micro-arc oxidation (MAO), and combined ESD + MAO coating methods to improve mechanical properties and wear resistance. The results obtained from the coatings were compared with the bare Ti6Al4V. The phase structure, surface-cross sectional morphologies, elemental distribution, surface-cross sectional mechanical and wear properties of the bare alloy and the coatings were investigated by XRD, SEM, EDX-mapping, nanoindentation, micro-Vickers hardness, and tribometer. The XRD results revealed that the MAO and ESD + MAO duplex coatings contained rutile-TiO2 and & gamma;-Al2O3 phases, while Al3Ti, Al2Ti, and AlTi3 phases were observed in the ESD coating. The average hardness of all coatings was significantly improved with respect to bare Ti6Al4V due to the crystalline and dense structure of the inner layer. In addition, the wear resistance of the coatings was significantly improved compared to that of bare Ti6Al4V.