Milling of nickel-based superalloys using throttle cryogenic cooling and micro-lubrication

Abstract. Nickel-based alloys are known to mount intense heat around the cutting edges of the cutting tool owing to their high yield strength, comparatively low thermal conductivity, and a significant seizure of the chip at the rake face even at low cutting speeds. Their sustainable machining demands a highly effective heat dissipation system. Due to its rich cooling potential, the compressed CO2-based throttle cryogenic cooling system is a prime contender. The presented work seeks a sustainable milling solution for the cutting of the following three nickel-rich allows using the combination of throttle cryogenic cooling and minimum quantity of lubrication: Inconel 718, Incoloy 825, and Waspaloy. The experimental study quantifies the effects of the lubri-cooling approach and cutting speed on tool wear, cutting forces, and workpiece surface roughness. The novelty of the work lies in the mutual comparison of the machinability of the three alloys of nickel and the application of the cryogenic coolant in the form of pulses in addition to the conventional mode of continuous stream. The analyses of the experimental results suggest that the pulsed mode of the coolant, especially in combination with the lubricant, outperforms the continuous mode of the coolant’s supply regarding cutting forces and work surface roughness. Additionally, the study has yielded mixed results regarding tool wear for different combinations of workpiece material and cutting speed. Nonetheless, dry milling of the three alloys proved to be absolutely unsustainable in comparison to either of the two modes of throttle cryogenic cooling, with or without the application of micro-lubrication.