Enhanced wear and corrosion resistance in Ti3Al-based nanocomposite coatings via oxidation-induced structural evolution

In this study, a multifunctional (Ti,Al,Cr,Si)-O nanocomposite coating was synthesized via cathodic arc evaporation (CAE) at a low substrate temperature of 150 °C, enabling deposition on thermally sensitive substrates. The as-deposited coating features nanocrystalline α 2 -Ti 3 Al-based domains (∼5.2 nm) embedded in an amorphous oxidic matrix. Post-deposition annealing at 800 °C for 2 h in ambient air significantly transforms the coating, promoting the formation of a compact layer-by-layer oxide scale enriched with crystalline TiO 2 and amorphous Al 2 O 3 nano-needles. This thermal treatment enhances the coating’s hardness and modulus from 12.4 ± 2.6 GPa to 28.2 ± 6.8 GPa and from 174 ± 20 to 318 ± 52 GPa, respectively, resulting from a hard oxide scale consisting of needle-like features and layer-by-layer architecture, the development of more crystalline islands, the formation of nano-twins, and the transformation of residual tensile stress into compressive stress. Ball-on-disk tests reveal wear rate reductions from 2.55×10 -4 to 0.86×10 -4 mm 3 /N·m (dry) and from 1.71×10 -4 to 1.37×10 -4 mm 3 /N·m (NaCl solution), accompanied by reduced friction coefficients. High-temperature wear testing (800 °C) further confirms the coating’s durability in thermally demanding conditions. Additionally, the annealed coating exhibits super-hydrophobic behavior, with a water contact angle of 151.2 ± 0.9°, and shows significantly improved corrosion resistance—achieving up to three orders of magnitude lower corrosion current densities and nobler corrosion potentials in both 3.5 wt% NaCl and 0.1 M H 2 SO 4 solutions. These improvements arise from the formation of a chemically inert and dense layer-by-layer ceramic oxide scale, super-hydrophobicity, the sealing of surface defects through oxidation-induced morphological changes.