Experimental investigation and statistical modelling of cutting temperature with surface and tool morphological analyses in laser-assisted turning of Inconel X-750

Abstract

Inconel X-750 is extensively used in aerospace, nuclear and power generation industries because of its excellent mechanical strength and oxidation resistance at elevated temperatures. However, its high strength, work-hardening tendency and poor thermal conductivity make conventional machining difficult. Laser-assisted turning (LAT) has been widely adopted to improve the machinability of hard-to-cut materials. The influence of machining parameters on cutting temperature and the associated changes in surface and tool morphology during LAT of Inconel X-750 have not been systematically investigated. In this study, LAT experiments were performed on Inconel X-750 using a Taguchi L27 orthogonal array by considering laser power, spindle speed, feed rate and depth of cut (DoC) as the machining variables, with cutting temperature selected as the primary response. The experimental data were analysed using analysis of variance and regression analysis to establish the relationship between machining parameters and cutting temperature. Scanning electron microscopy and microhardness measurements were used to characterize the machined surface and cutting tool. Laser power had the greatest influence on cutting temperature, contributing 84.11%, followed by DoC (6.38%). The regression model showed good agreement with the experimental results, with an R 2 value of 97.57%. The validation test confirmed the model with an accuracy of 94.83%. Moderate cutting temperatures produced more uniform surface morphology, whereas excessive temperatures promoted material smearing, adhesion and diffusion-related changes on the cutting tool. LAT reduced the microhardness because of thermal softening, although the hardness remained above the annealed condition of the alloy.