Investigations on pulsed and continuous supply of a cryogenic medium in milling of Waspaloy and Inconel 718 under various lubri-cooling environments

In the machining process, the buildup of heat around the cutting edge significantly impacts the outcome, causing adverse effects like micro-cracks, heightened tool wear, and diminished surface quality of the workpiece. To counter these challenges, the application of cutting fluids, particularly through flood cooling, is a common practice. However, it is crucial to acknowledge that the utilization of these fluids poses health and environmental risks. This research work reports on implementing a cryogenic cooling method that deploys carbon dioxide (CO2) in continuous and pulsed modes with and without introducing micro-lubrication for machining Waspaloy and Inconel 718. The influence of cutting speed and five lubri-cooling methods is investigated on flank wear, cutting forces, and average arithmetic roughness for a side milling operation. It turned out that minimum tool wear in the milling of Waspaloy is observed for the pulsed application of the coolant, with and without the parallel application of micro-lubrication. The lowest forces are also observed under CO2-Pulse-MQL in the milling of Waspaloy, whereas CO2-Pulse-MQL and CO2-Cont-MQL (continuous impingement of CO2 along with the application of micro-lubrication) resulted in the lowest forces during machining of Inconel 718 under low and high levels of cutting speeds respectively. The application of micro-lubrication has clearly shown the potential for reducing the cutting forces in the cutting of both alloys. It is also found to have reduced the surface roughness at the low level of cutting speed. Over all. Minimum surface roughness of 0.792 µm was found in CO2-Cont-MQL cooling approach. For Waspalloy, CO2-pulse MQL lubricooling approach yielded Minimum Ra of 0.907 µm, Minimum Wear of 58.11 µm, and Minimum Force (Fx) of 148 N. The lowest surface roughness values for Waspaloy and Inconel 718 were recorded under CO2-Cont-MQL and CO2-Pulse-MQL modes, respectively. From a holistic perspective, the CO2-Pulse-MQL mode is identified as the best lubri-cooling option for the milling of the two nickel-based super-alloys.