Enhancing the wear resistance of arc-deposited AlTiN coatings via heat treatment with oxygen diffusion

The wear resistance of the coating is a key indicator for assessing the cutting performance of coated tools. In this study, an AlTiN coating deposited via arc evaporation was exposed to low-temperature (≤600 °C) thermal treatment in air. After low-temperature heat treatment in air, the oxygen content in the coating exhibited a gradient distribution, decreasing from the outer surface to the inner layers. The diffused oxygen in the AlTiN coating did not significantly alter its surface morphology or phase composition, but it did influence the preferential growth of grains. Specifically, a portion of the diffused oxygen entered the crystal lattice of the nitride, while another part formed amorphous aluminum oxide at the grain boundaries. These changes enhanced the nanohardness, the bonding strength between the coating and the substrate, and wear resistance of the coating. Notably, the wear resistance improved significantly, with the wear rate decreasing from 7.0 × 10⁻¹⁵ m³/N·m for the as-deposited coating to 3.2 × 10⁻¹⁵ m³/N·m for the coating treated at 500 °C. The oxygen diffusion heat treatment caused the wear mechanism of the coating to shift from predominantly adhesive wear and abrasive wear to a combination of oxidation and abrasive wear.