Optimizing cutting parameters in minimum quantity of lubrication milling of hardened cold work tool steel

Abstract

Despite the numerous advantages offered by high-speed and high-performance cutting technologies, the issue of diminished tool life still remains profoundly concerning, especially in the case of machining hardened steels. Moreover, in finish machining, the requirement of improving workpiece surface finish also gains considerable importance. Application of the minimum quantity of lubrication (MQL) has delivered so many benefits that it has almost become part and parcel of turning, drilling, and milling technologies. In this research work, the high-speed milling of hardened cold work tool steel (62 HRc), under an MQL environment, was experimentally investigated and a response surface methodology was utilized to optimize the cutting parameters. A series of experiments was performed in order to quantify the effects of following three cutting parameters on tool life and arithmetic average surface roughness: cutting speed ( Vc), feed rate ( fz), and radial depth of cut ( ae). The surface roughness was measured in two directions: along the feed, Ra, and along the pick-feed, Ra(pick). Analysis of variance (ANOVA) performed on the data revealed that the effect of cutting speed was significant on tool life as well as on Ra. Moreover, the effects of feed rate and radial depth of cut on tool life and Ra(pick) respectively were found to be significant. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) analyses were performed to determine the dependence of different tool damage modes on levels of cutting parameters utilized. It was found that chipping and adhesion were the dominant tool damage modes in most of the experimental runs and their severity was dependent on levels of feed rate and cutting speed respectively.