Cryogenic machining is a cleaner processing technology which uses cryogenic coolants such as liquid nitrogen for cooling in material cutting process. It is widely used in the processing of difficult-to-machine metal materials in aerospace and other fields to solve problems such as insufficient cooling efficiency and poor machining quality during conventional cooling processing for these materials. In order to clarify the effect law of cryogenic machining on the surface integrity of difficult-to-machine metal materials

this paper particularly reviews the research progress in the analysis of surface roughness

micromorphology

microstructure

microhardness and residual stress of such materials under different cooling conditions. The results show that cryogenic coolant can take away a large amount of cutting heat and reduce tool wear

thus reducing the machined surface roughness

inhibiting surface defects

promoting grain refinement

improving microhardness and increasing residual compressive stress. Finally

researches on the surface integrity of cryogenic machining are summarized

and works which have not been carried out in relevant aspects are prospected.