Investigation of biodegradable oil–based MQL parameters for sustainable grinding of H13 die steel using MCDM techniques

Abstract

Precision tooling industries have seen a growing demand for biodegradable cutting fluid in minimum quantity lubrication (MQL)–based abrasive finishing of difficult-to-cut materials due to sustainable ISO 14000 regulations, which highlight the power consumption and environmental and health concerns of workers. However, the mist quality in MQL is governed by spray factors such as air pressure (Pa), biodegradable oil flow rate (Qoil), and nozzle position from the cutting zone (Pn), which significantly impacts on grindability and surface integrity of the ground components. Therefore, optimal MQL machining attributes using multi-criteria decision-making (MCDM) are sparsely defined in previous studies. This study addresses this gap by identifying the optimal MQL attributes for precision grinding heat-treated AISI H13 hot die steel using MCDM frameworks like Entropy, TOPSIS, and VIKOR. The novel insights of MCDM technique reveal that an optimal MQL setting includes Pa = 4 bar, Qoil = 150 ml/h, and Pn = 40 mm, which minimises tangential grinding force (25.9 N), cutting temperature (84 °C), and surface roughness (Ra = 0.255 µm) while maximising the bearing area ratio (81.02%). A comprehensive sensitivity analysis further establishes TOPSIS as the most robust and consistent selection tool under dynamic weighting scenarios. This work visualises biodegradable mist characteristics under optimised conditions, observing uniformly spherical droplets (average size = 49.65 µm) with a 12° inclined nozzle angle, which enhances convective heat dissipation in the grinding zone. Outstanding surface topography with negligible side material flow around the shearing tract and uniform tribological bearing area was found under optimal MQL conditions due to uniform lubricated vapor film formation and faster heat extraction through biodegradable-based mist at the cutting zone. These insights may direct the tooling industries toward effective, sustainable grinding, reducing manufacturing cycle times and promoting environmental cleanliness. © The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2025.