Experimental results on the performance of cryogenic treatment of tool and minimum quantity lubrication for machinability improvement in the turning of Inconel 718

Inconel 718 is a popular, but difficult to machine, nickel-based supper alloy. Machining performance of this material can be improved by appropriate modelling and optimization. In the present study, response surface modelling and optimization for turning of Inconel 718 under four machining conditions: dry with untreated inserts, dry with cryogenically treated inserts, minimum quantity lubrication with untreated inserts and minimum quantity lubrication with cryogenically treated inserts is carried out. With the aim of improving the machinability of Inconel 718, an attempt has been made to examine the effect of cryogenic treatment of tool and minimum quantity lubrication in terms of indicators such as surface quality of workpiece, tool wear and material removal rate. Cutting speed, feed rate and depth of cut are used as the control parameters. Whereas, cutting force, tool vibration, cutting temperature, surface roughness and tool wear are the measured responses. Prediction models are developed for each response. Later, all the responses are optimized together by desirability approach and are validated using confirmation experiments. A spider plot is drawn to display the relationships among control and response parameters. The plot shows that application of minimum quantity lubrication with cryogenically treated inserts resulted in least cutting force, tool vibration, cutting temperature, minimum surface roughness of workpiece along with least tool wear and best material removal rate compared to other three conditions used. This clearly shows machinability improvement of Inconel 718.