Machinability assessment and optimization of turning AISI H11 steel under various minimum quantity lubrication (MQL) conditions using nanofluids

Abstract

This paper presents an investigation into the machinability of hot work tool steel AISI H11 (DIN 1.2343). Experiments were conducted under different environments: dry cutting, minimum quantity lubrication (MQL) using vegetable oil, and two MQL configurations with nanofluids (NF-MQL), one containing hexagonal boron nitride (hBN) and the other containing multi-walled carbon nanotubes (MWCNT). The factors studied include cooling condition (CC), flow rate (F-r), nozzle distance (N-d), nozzle angle (N-a), as well as cutting speed (V-c) and feed (f). The Taguchi L16 orthogonal array, analysis of variance (ANOVA), response surface methodology (RSM), grey relational analysis (GRA), and desirability function (DF) were employed to evaluate the turning process performance, namely surface roughness, cutting temperature, and total energy consumption. The results demonstrate that MWCNT nanoparticles in vegetable oil within the MQL system effectively reduce surface roughness and cutting temperature, while hBN nanoparticles decrease energy consumption. In this context, free nanoparticles in the MQL act as additional nano-tools for material removal, supplementing the cutting edge of the tool. Under these conditions, turning becomes a combined cutting and polishing operation due to the presence of free nanoparticles and micro-chips in the contact zone, offering superior performance compared to dry turning or conventional MQL alone.