Recent advances in cryogenic machining of difficult-to-machine materials

Difficult-to-machine materials suffer from high cutting temperatures, large mechanical loads, severe tool wear and poor deformation controllability. Conventional flood cooling has limitations in efficiency and sustainability. Cryogenic machining offers an effective solution by regulating thermomechanical interactions. Unlike previous reviews focused on equipment or macroscopic performance, this review establishes a mechanism‑oriented framework linking ultra‑low‑temperature machining (thermal regulation), cryogenic minimum quantity lubrication (interfacial regulation) and ice‑assisted machining (structural regulation). The article systematically examines these three techniques regarding cutting temperature/force, chip formation and fracture, tool wear evolution, surface integrity and deformation suppression. Emphasis is placed on titanium alloys, nickel‑based superalloys, aluminum alloys and composites; studies on steels, ceramics and other materials are included only for mechanistic comparison or methodological reference. Results show that cryogenic machining suppresses thermal softening and adhesive wear, improves chip fracture, reduces temperature and load, prolongs tool life and generates favorable compressive residual stress. For thin‑walled components, ice‑assisted machining enhances stability and suppresses deformation and burr formation via cryogenic cooling and phase‑change constraint. Finally, challenges in stability and scalability are analyzed, and future directions are proposed, including deformation suppression, cooling‑lubrication‑constraint synergy and green manufacturing applications.