Microstructure and corrosion resistance of duplex coatings deposited on TC17 alloys by MAO and HiPIMS

In this paper, the TiN single-layer and Ti/TiN multilayer were severally deposited on the MAO-coated Ti-5Al-2Sn-2Zr-4Mo-4Cr (TC17) alloy via micro arc oxidation (MAO) followed by a high power impulse magnetron sputtering (HiPIMS) process. The effects of the duplex titanium nitride-based layers on microstructures, elements distribution, phase composition and corrosion resistance of the MAO-based coatings were examined. The results revealed that the inevitable deficiencies such as cavities, open-pores and micro-cracks formed on the porous layer were efficiently sealed by the deposited layers, suggesting the arranged duplex coating strategy is appropriate for applying high hard TiN coating with satisfied interface quality and superior banding strength to soft TC17 substrate. The corrosion tests demonstrated that the multilayered MAO-(Ti/TiN) coating could effectively prevent the penetration of corrosive ions and be capable of maintaining a visibly higher E-corr and lower I-pass, providing the best protective efficiency to TC17 alloys.