Effect of different cooling and lubrication strategies on milling performance of ultra-high strength steel

Ultra-high strength steel is the major material for manufacturing the aviation gears due to its superior strength and high hardness. However, the generous usage of cutting fluid in flood cooling resulted in the increase of machining costs and environmental pollution problems during the milling process of ultra-high strength steel. The green cutting technology was widely utilized to improve the machining performance of difficult-to-cut materials and reduce the harm to the environment, thus achieving the goal of clean production. In this study, the effect of three green cooling and lubrication conditions (i.e., dry cutting, high-pressure air cooling (HPAC) and ultrasonic atomized-based cutting fluid (UACF)) on the milling performance of ultra-high strength steel was evaluated in terms of milling force, surface quality, and tool wear. Further, the fast Fourier transform (FFT) algorithm was also applied to quantitatively analyze the milling chatter and profile features of machined surface. The obtained results show that the UACF process obtains a lower cutting force, coefficient of friction, and surface roughness R-a in comparison with the dry and HPAC environments. In addition, UACF can suppress the machining chatter and reduce surface defects due to effective cooling and lubrication. Moreover, the improvement of cooling and lubrication resulting from the effective penetration of droplets in the UACF process contributed to the reduction of the tool wear concerning the formation of built-up edge and coating detachment. The UACF has shown the significant advantage in the green manufacturing of ultra-high strength steel.