Experimental investigation and multi-criteria optimization of rough and finish milling for AISI 316L stainless steel: A focus on surface integrity, temperature, and tool performance

This study experimentally investigates the machinability of AISI 316L austenitic stainless steel under dry and air-assisted cooling during rough and finish milling. A high-feed milling cutter was employed for roughing and a solid carbide end mill for finishing. Cutting temperature, surface roughness, and tool wear were evaluated using thermal imaging, profilometry, and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS). The results demonstrate that air-assisted cooling significantly reduces thermal loads and tool wear. Specifically, during rough milling, air cooling lowered average cutting temperatures by approximately 27% (from 150°C to 110°C) and maximum temperatures by 24% (from 267°C to 204°C). In finish milling, average and maximum temperatures decreased by 33% (from 194°C to 129°C) and 35% (from 272°C to 177°C), respectively. Surface quality improved notably under air cooling, with reductions in average roughness (Ra) by 21%, maximum height (Rz) by 35%, and total height (Rt) by 46%. SEM/EDS analyses revealed that air cooling minimized coating delamination, adhesion, and oxidative wear. A hybrid multi-criteria decision-making (MCDM) approach integrating the CRITIC and ARAS methods was applied to optimize the process parameters. The optimum condition – air cooling, 4375 rpm spindle speed, and 500 mm/min feed – achieved the highest relative utility (Ki = 0.895), balancing material removal rate, surface finish, and thermal performance. This study concludes that air-assisted cooling is a sustainable and effective strategy for enhancing surface integrity and tool life in the milling of difficult-to-machine materials such as AISI 316L. © IMechE 2026