Oxidation resistance of quintuple Ti-Al-Si-C-N coatings and associated mechanism

The oxidation behavior of Ti-Al-Si-C-N hard coatings with different Al contents deposited on high-speed steel and Si substrates by hybrid arc-enhanced magnetron sputtering is investigated in the temperature range of 500 °C–1000 °C. The coating hardness is maintained at around 35 GPa, and the parabolic oxidation rate constant Kp at 1000 °C decreases to 3.36 × 10−10 kg2 m−4 s−1 when the Al concentration is increased to 30 at. %, indicating that Ti-Al-Si-C-N coatings with larger Al concentrations have better oxidation resistance. X-ray diffraction, cross-sectional scanning electron microscopy, and x-ray photoelectron spectroscopy reveal a protective surface layer consisting of Al2O3, TiO2, and SiO2 that retards inward oxygen diffusion. A mechanism is proposed to elucidate the oxide formation. As a consequence of the good oxidation resistance, the Ti-Al-Si-C-N coatings have a large potential in high-speed dry cutting as well as other high temperature applications.