Experimental investigations and multi-objective optimization of MQL-assisted milling process for finishing of AISI 4340 steel

Abstract

The purpose of this study is to investigate solid lubricant-assisted cutting fluids applied through minimum quantity lubrication technique (MQL) for nano-finishing of AISI 4340 steel using TiCN/Al2O3/TiN chemical vapor deposition coated tungsten carbide inserts during flat end milling process. Four different types of cutting fluids were examined, namely pure emulsion, boric acid dissolved in the emulsion, graphite suspended in the emulsion and hybrid solid-liquid minimum quantity lubrication. Optimization of the flat end milling process was done through single performance Taguchi analysis as well as through a multi-performance Taguchi-Gray relational analysis (TGRA). The hybrid TGRA technique was utilized to get the optimum level of input parameters and to get the knowledge about the significance of the input parameters considering both of the responses simultaneously. The results of the hybrid analysis were confirmed by multi-objective genetic algorithm. Novel and physically based analytical interpretation of the results was provided. Low viscosity fluids were found to provide better results during MQL application. The results lead to cleaner and sustainable production aiming at reducing/omitting waste and making the process environment-friendly.