TiN doped micro-arc oxidation coating on titanium alloy surfaces

High-quality micro-arc oxidation (MAO) coatings are a key research direction for aerospace titanium alloy TA15, but there is still a lack of research on the influence of adding different contents of TiN to the electrolyte on coating performance. To clarify the regulation mechanism of TiN doping on the microstructure and interface properties of MAO coatings, MAO coatings with TiN doping amounts of 0, 0.2, 0.5, and 1 g/L were prepared. Combined with macroscopic morphology observation, phase composition analysis, and energy dispersive spectrometer element distribution characterization, the influence of the TiN doping amount on the coating performance was systematically investigated. The results show that when the doping amount is 0 g/L, the coating thickness is about 33 μm ± 10%, the surface is smooth, with low roughness, and the interface between the coating and the substrate is straight. When the doping amount is 0.2 g/L, the microstructure of the coating is optimal, the surface maintains excellent smoothness, the bonding interface appears irregular and wave-like, there are no obvious cracks inside, and the mass percentage of O is 25.6%. When the doping amount is 0.5 g/L, the coating cannot form a complete continuous structure, and only local discrete oxidation products are present. When the doping amount is 1 g/L, the surface smoothness of the coating significantly decreases, and there are noticeable thickness differences. A uniform and continuous coating was formed on the surface at a concentration of 0.2 g/L. The pore sizes were moderate and evenly distributed, and the melting morphology at the pore edges was regular and complete. When 0 g/L of dopant is added, the titanium matrix undergoes gradual oxidation to form a TiO2, Ti2O3, and Ti phase system. After doping with TiN, TiN is found in the coating, which promotes the formation of TiO2. This study provides theoretical guidance and technical support for regulating the structure-performance relationship and improving key properties such as mechanics and corrosion resistance of titanium alloy MAO coatings.