Experimental and numerical study on tribological behavior and machinability in titanium indirect cryogenic machining with minimum quantity lubrication

Cryogenic machining involves spraying cryogenic coolants to reduce the cutting tool temperature. In this study, cryogenic machining was applied to a titanium alloy with minimum quantity lubrication (MQL), and the tribological and machining performance were evaluated. As side-down milling was performed, the effects of cryogenic cooling and MQL were experimentally and numerically investigated with long machining distances (40, 000 mm), and the cutting force, tool wear, and tool temperature were analyzed. Compared to the wet condition, under the cryoMQL condition, which represents the simultaneous application of cryogenic cooling and MQL, the cutting force and flank wear length decreased by up to 17.7% and 46.4%, respectively. The cryogenically cooled and lubricated cutting tool enhanced the tribological performance, slowing tool wear. The reduced surface friction of the tool and tool wear decreased the frictional force and changed the trend of the cutting force according to the machining distance. The cryoMQL milling was simulated using DEFORM software. In the numerical study, a decrease in the tool temperature, which affects the reduction in cutting force and tool wear, was observed under cryoMQL conditions. The maximum tool temperature was reduced by 46.5% compared with that under wet conditions.