Side-milling of Incoloy 825 under pulsed and continuous modes of cryogenic cooling

Abstract

Heat accumulated around the cutting edge significantly impacts the machining process. It results in microcracks development, tool wear enhancement, and work surface quality deterioration. These issues can be somewhat counteracted by applying a cutting fluid at the cutting zones through flood cooling. Cutting fluid waste, however, can be significant and negatively influence the environment. To enhance the effectiveness, a throttle cryogenic coolant (carbon dioxide) is innovatively applied in a pulsed mode on the cutting zone in the milling of Incoloy 825. The pulsed mode of application is realized by periodically opening and closing the supply of the coolant for a given period. The efficacy of the novel system is compared with the conventional approach of applying the cryogenic coolant in the form of a continuous stream. Additionally, the effects of the cutting fluid are also investigated after parallelly adding the stream of micro-lubrication to both modes of the coolant's supply. The effects are investigated on the performance measures of tool wear, cutting forces, and milled surface roughness at the two levels of cutting speed. The experimental results indicated that of the five lubri-cooling techniques tested, the pulsed mode combined with micro-lubrication yielded the lowest cutting forces and the best surface quality. On the other hand, the continuous mode (without micro-lubrication) yielded the best results regarding tool damage. The analyses have also revealed that the parallel application of micro-lubrication in addition to the cryogenic coolant has caused favorable effects on all the performance measures when the coolant is applied in the pulsed mode. Furthermore, the favorable effect is generally more prominent at the low level of cutting speed. In a nutshell, proof of concept is provided in favor of an innovative mode of applying a cryogenic coolant in the form of pulses combined with micro-lubrication for enhancing the viability of milling a nickel-based superalloy.