Thermal Loads and Surface Quality Evaluation in Machining of Hardened Die Steel under Dry and Cryogenic Machining

AISI H13 die steel is widely used in different industries because of its especial properties. During the machining of hard materials, some of the mechanical properties of the material are changed due to the generation of intensive thermo-mechanical loads and plastic deformation into the workpiece. Controlling these intensive changes in machined surfaces is an important task and significantly affects the performance of the machined part. In addition, surface roughness is one of the aspects of surface texture and affects the fatigue life of the material. Since machining of hard materials is a difficult procedure and it is confronted with several limitations, new methods in machining processes are essential to be developed. One of these methods is using cryogenic coolant where the machining temperature may be considerably reduced by spraying liquid nitrogen on the cutting region. Based on this, at the present study, the variation of thermal loads and surface roughness at different machining parameters were evaluated under dry and cryogenic conditions. To do this, a thermal infrared camera and liquid nitrogen delivery system was used during the machining of hardened AISI H13 steel. Compared with dry condition, the effectiveness of the cryogenic coolant on surface roughness and thermal loads were analysed and discussed at different cutting speed, feed rate, and depth of cut. Finally, it was found that, applying cryogenic coolant in machining of AISI H13 die steel can be very effective to enhance performance and quality of the machined component in terms of surface roughness and thermal loads.