Enhanced Wear and Corrosion Resistance of Nanocomposite Ti3al-Based Coatings Upon Oxidation at 800 °C

Abstract

Protective coatings for metallic components operating in harsh environments must simultaneously provide high mechanical strength, wear resistance, and corrosion protection—properties often limited by conventional ceramic or metallic films. 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 180 °C, enabling deposition on thermally sensitive substrates. The as-deposited coating features nanocrystalline α2-Ti3Al-based domains (~7.9 nm) embedded in an amorphous oxidic matrix containing 29.1 at.% oxygen overall. Post-deposition annealing at 800 °C for 2 h in ambient air significantly transforms the coating, promoting the formation of a compact oxide scale enriched with TiO2 and SiO2 nano-needles.This thermal treatment enhances the coating’s hardness and indentation modulus from 12.4±2.6 GPa to 28.2±6.8 GPa and from 174±20 to 318±52 GPa, respectively. Ball-on-disk tests reveal wear rate reductions from 2.55×10-4 to 0.86×10-4 mm3/N·m (dry) and from 1.71×10-4 to 1.37×10-4 mm3/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 150.1°, and shows significantly improved corrosion resistance—achieving up to two orders of magnitude lower corrosion current densities and nobler corrosion potentials in both 3.5 wt% NaCl and 0.1 M H2SO4 solutions. These improvements stem from the formation of a chemically inert, dense ceramic oxide layer and the sealing of surface defects through oxidation-induced morphological changes.