• • After 800 °C static oxidation, the AlCrN/TiSiN coating forms porous TiO/TiO2 and o-SiO2 phases, whereas the AlCrN/TiSiN/AlCrTiSiON multilayer retains sharp protective oxide peaks and strong fcc-TiN/fcc-CrN reflections, confirming that the pre-oxidized barrier prevents catastrophic phase degradation and extends tool life in high-temperature dry cutting.
• • Hardness, H/E, and H3/E*2 peak at 49.64 GPa, 0.102, and 0.426 GPa respectively after 600 °C oxidation, while critical load reaches 85 N after 700 °C oxidation, indicating that the oxide layer optimizes mechanical integrity at intermediate temperatures, which is critical for maintaining cutting edge stability during intermittent machining.
• • At 700 °C friction, the wear rate minimizes at 2.28×10−10 mm3/(N·mm), and at 800 °C the friction coefficient drops to 0.63, demonstrating that the tribo-oxide layer provides effective lubrication and wear resistance at elevated temperatures, reducing frictional heat and prolonging tool life in high-speed dry milling.
• • In dry milling of hardened 45 steel, the AlCrN/TiSiN/AlCrTiSiON tool exhibits 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, with a 68 °C lower cutting temperature at 120 min, directly translating to reduced downtime and higher productivity in industrial machining.