Toward sustainable manufacturing: A triple-bottom-line review of dry machining of titanium alloys

Abstract

Titanium alloys are vital in aerospace, biomedical, and energy sectors due to their high strength and corrosion resistance. However, their poor machinability and the environmental impacts of conventional coolants necessitate sustainable alternatives. This review critically evaluates the dry machining of titanium alloys through the triple-bottom-line (TBL) framework—addressing ecological, economic, and social dimensions. It examines the roles of advanced coatings, surface texturing, and solid lubricants in overcoming thermal and tribological barriers in fluid-free conditions. Furthermore, process-assisted techniques, including cryogenic tool treatment (CTT), ultrasonic vibration-assisted (UVAM), and laser-assisted machining (LAM), are analyzed regarding tool life and energy efficiency. Comparative assessments reveal that while dry machining eliminates coolant waste, hybrid systems like Minimum Quantity Lubrication (MQL) and cryogenic cooling often provide a superior sustainability balance, despite trade-offs like nanoparticle toxicity or cryogen energy costs. The review concludes that achieving truly sustainable titanium machining requires an integrated approach involving eco-efficient tool design, digital optimization, and rigorous life-cycle assessment (LCA) to align manufacturing performance with global sustainability goals.