Extreme-load, high-temperature tribological analysis of Al-Si solid lubricant coatings for seizure prevention

• Al-Si coated WC prevented seizure at 2 GPa and 800 °C, outperforming uncoated WC. • Al-O-Si tribolayer formation enhanced lubrication and thermal barriers. • Al-Si coated WC balls significantly reduced work hardening in Inconel 718 coupon. • FEM confirmed Al-Si redistributed contact stresses, mitigating surface damage. Designing solid lubricants capable of operating under the extreme conditions encountered in processes such as machining remains a longstanding challenge, with seizure and surface damage continuing to cause significant economic and environmental losses. In this study, an Al-Si metallic coating is proposed as a candidate for lubrication under such conditions, and its tribological and mechanical performance is evaluated under combined high load and temperature condition for the first time. Experiments were conducted using a custom Joule-heated tribometer under transient extreme conditions (700 N load, approximately 2 GPa contact pressure, 200–800 °C), complemented by finite element simulations and post-test characterization, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and subsurface nanoindentation. The Al-Si coating suppresses seizure and maintains a significantly lower and stable coefficient of friction, with only a moderate increase at elevated temperatures linked to substrate degradation. X-ray photoelectron spectroscopy reveals the formation of thermally stable, lubricious tribofilms, while microstructural analysis shows reduced plastic deformation and subsurface damage. Simulations confirm reduced surface stresses and improved load distribution. These findings demonstrate that metallic lubricants can operate effectively under extreme loads and temperatures, establishing Al-Si alloys as a promising pathway for solid lubrication in extreme environments and more sustainable manufacturing.