Experimental investigation on performance of cryogenic, MQL and Nano-Coolant machining environment in turning of inconel 718

Purpose This study aims to investigate the effect of various advanced cooling techniques on the machinability of Inconel 718, a nickel-based superalloy known for its high strength, poor thermal conductivity, work hardening and rapid tool wear which make it difficult to machine especially under dry or conventional cooling conditions. The objective is to compare dry machining, minimum quantity lubrication (MQL), cryogenic cooling, nanofluids and their hybrids – particularly cryogenic-nanofluid MQL (cryo-nMQL) – to identify the most effective strategy for enhancing machining performance. Design/methodology/approach Nanofluids containing carbon nanotubes (CNT) and aluminum oxide (Al2O3) were prepared using a three-step dispersion method. Turning tests were conducted on Inconel 718 at a constant cutting speed of 70?m/min, 0.1?mm/rev feed and 0.3?mm depth of cut under 16 different cooling conditions. Tool-chip temperature, surface roughness (Ra) and flank wear were measured using an infrared camera, profilometer and optical microscope for machining performance evaluation. SEM and EDX analyses were used to study wear mechanisms. Findings Cryo-nMQL with 0.5 vol% CNT nanofluid yielded superior performance, reducing tool-chip interface temperature by 59.3%, surface roughness by 42.8% and tool wear by 66.5% compared to dry machining. CNT-based nanofluids performed better than Al2O3 due to higher thermal conductivity and a ball-bearing effect. Higher nanoparticle concentration increased viscosity, reducing effectiveness. SEM confirmed adhesion, notch wear and chipping as dominant wear mechanisms. Originality/value The novelty of this study lies in demonstrating the effectiveness of cryo-nMQL with CNT nanofluids for significantly enhancing the machining of difficult-to-machine materials like Inconel 718, offering a sustainable and efficient cooling strategy. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2025-0096/