High-temperature oxidation kinetics and microstructural evolution of detonation-sprayed AlCuFe quasicrystalline coatings

Abstract

To solve the susceptibility of TC4 titanium alloys to high-temperature oxidation and subsequent performance degradation, AlCuFe quasicrystalline (QC) coatings were successfully fabricated via detonation spraying (DS) as a functional protective barrier. The oxidation kinetics, phase evolution, and mechanical stability of the coating system were systematically investigated at 450°C in an atmospheric environment for up to 250 h. The results indicate that the oxidation kinetics strictly obey the parabolic growth law, yielding a steady-state parabolic rate constant (k_p) of 1.83 × 10⁻² mg² ⋅ cm⁻⁴ ⋅ h⁻¹. Throughout the service period, the coating exhibits a significant “thermal hardening” effect, with the surface microhardness increasing from an initial 491 HV_0.2 to a final value of 665.2 HV_0.2 (a 35.5% increment). Phase evolution is characterized by an initial thermally induced ordering of metastable regions (0–3 h) followed by the gradual decomposition of the icosahedral (I) phase into approximant phases (β, τ, and λ) driven by the Al-depletion effect. Notably, the increased density of phase boundaries and intermetallic interfaces within the multi-phase network effectively sustains the mechanical performance despite the decline in the primary QC fraction. This study demonstrates that DS-AlCuFe coatings provide a reliable structural evolution pathway for the long-term high-temperature protection of titanium alloys.