Thermal Stability and Cutting Performance of AlCrN/TiSiN/AlCrTiSiON Multilayer Tool Coating
High-speed dry cutting of hardened steel imposes severe oxidative and diffusion wear on AlCrN/TiSiN-coated tools, limiting service life. This study introduces a multilayer composite plus pre-oxidation strategy: an AlCrN/TiSiN coating deposited by arc ion plating is subjected to controlled pre-oxidation, forming an in-situ AlCrTiSiON oxide barrier. Static oxidation, high-temperature tribological tests, and dry milling of hardened 45 steel evaluate performance. After 800 °C oxidation, the AlCrN/TiSiN coating develops porous TiO/TiO2 and o-SiO2 phases, while the multilayer coating retains sharp protective oxide peaks and strong fcc-TiN/fcc-CrN reflections. Hardness peaks at 49.64 GPa after 600 °C oxidation, with H/E = 0.102 and H3/E*2 = 0.426 GPa. Critical load reaches 85 N after 700 °C oxidation. At 700 °C friction, wear rate minimizes at 2.28×10−10 mm3/(N·mm); at 800 °C, friction coefficient drops to 0.63. In dry milling, the multilayer tool achieves a wear band of only 60.66 μm after 90 min, and a cutting life 13.83 times that of uncoated and 3.46 times that of AlCrN/TiSiN-coated tools. Cutting temperature is reduced by 68 °C at 120 min compared to the AlCrN/TiSiN coating. The pre-oxidized oxide layer suppresses oxygen inward diffusion and heat conduction, enhancing structural stability and tool longevity.