Application of novel soft solid lubricant coatings on turning tools for sustainable and high-performance machining of INC 718 alloy: A new efficient fluid-free method

This study introduces the application of a novel class of soft solid metallic lubricant coatings on hard-coated cutting tools to enable high-performance, fluid-free machining of Inconel 718. By employing a novel in-situ coating technique, the Al-Si lubricant coating was applied to commercially available AlTiN-coated tools within a CNC machine in just seconds. The Al-Si-coated tools demonstrated significantly improved performance in dry machining compared to conventional wet and dry methods. The deposition of a top layer of Al-Si on AlTiN-coated tools resulted in significantly lower cutting forces and enhanced tool life compared to both dry and wet machining conditions, achieving a 64 % increase in tool life over dry conditions. Analysis of worn tools via FIB-SEM revealed that the Al-Si coating preserved the underlying AlTiN layer, which was otherwise depleted under harsh dry conditions. Surface analysis also revealed considerably improved surface integrity compared to wet and dry machining with TiAlN tools, with the Al-Si layer reducing surface defects and minimizing machining-induced microstructural changes. EBSD analysis demonstrated less microstructural deformation and misorientation in the workpiece, indicating better preservation of material properties. This innovative coating approach not only enhances tool performance and durability but also supports sustainable machining by eliminating the need for fluid-based lubricants, reducing waste, and minimizing environmental impact. Overall, the findings support the effectiveness of the Al-Si coating in facilitating the dry machining of challenging materials like Inconel 718, offering a new solution for reducing waste and promoting more sustainable machining practices.