End milling of DIN 1.2714 die steel with cryogenic CO2 cooling

Abstract

Currently, cryogenic coolants are used instead of normal cutting fluid in transferring excessive heat from the cutting region and retaining cutting tool edge sharpness during the machining process, and to eliminate the hazardous effects of cutting fluids. In this investigation, end milling experiments with various cooling approaches were performed on DIN 1.2714 die steel using titanium aluminum nitrate-coated carbide tool inserts under dry, conventional coolant, and cryogenic CO2 environments. The end milling performance under CO2 environment has been compared with those under dry and wet conditions regarding cutting temperature (Tc), feed force (Fx), normal force (Fy), axial force (Fz), surface roughness (Ra), tool wear, surface and chip morphology, and residual stress. The consequences of these machining environments were evaluated. Using cryogenic CO2 cooling technique reduced the Tc values by approximately 50.49 % and 64.42 % compared with those of wet and dry conditions, respectively. Similarly, CO2 cooling diminished the cutting forces, namely, Fx, Fy and Fz. As a result, Ra values reduced by approximately 59.81 % and 67.15 % compared with those of wet and dry conditions, respectively. Cryogenic CO2 caused a significant reduction in surface damage and abrasion wear in the machined surfaces and cutting inserts, respectively. No substantial changes in residual stress were observed at the cut surfaces.