Investigation of the effects of cryogenic cooling on drilling performance in drilling of Inconel 718 superalloy

In this study, the effects of cryogenic cooling on drilling performance in drilling of Inconel 718 which is a nickel-based superalloy were investigated experimentally. Drilling tests were performed at a constant cutting speed (10 m/min) and a feed (0.02 mm/rev) using uncoated and TiAlN coated solid carbide twist drills under cryogenic, traditional cutting fluid, and dry conditions. The effects of cooling/lubrication conditions and coating material were examined in terms of thrust force, torque, maximum temperature, burr formation, chip formation, subsurface deformed layer thickness, microhardness change and average surface roughness values. Cryogenic cooling significantly decreased the temperature values. In general, lower subsurface deformed layer thickness and burr formation at the hole entrance were obtained under cryogenic conditions. However, experimental results showed that cryogenic cooling increased the thrust force and the torque values and led to rapid tool wear. Therefore, burr formation at the hole exit also increased. Good surface roughness and low tool wear were achieved with the use of cutting fluid.