High-Speed Machining of Nickel-Based Alloy INVAR 36: Optimization of Machining Vibration, Tool, and Alloy Surface Characteristics

INVAR 36 is considered a difficult to machine alloy because of its physical properties, but it has a low coefficient of thermal expansion and good dimensional stability that makes it suitable for aerospace, precision engineering, and tooling applications. Dry turning experiments have been done on INVAR 36 based on different cutting speeds (v_c), feed rates (v_f), and depth of cuts (a_p) with respect to their influences on surface roughness (R_a), maximum flank wear (VB_max), and machining vibrations, Root Mean Square. Through Response Table Analysis, feed rate was found to be the highest influencing parameter for surface roughness, while cutting speed was the highest influencing parameter for tool wear and vibrations. Further, the vibration data have been studied through Fast Fourier Transform in frequency, domain with the dominant frequency being 105.6 Hz at optimal machining conditions. The optimization was carried out through multi-criteria decision-making by employing Grey Relational Analysis, Evaluation based on Distance from Average Solution, and Additive Ratio Assessment. It is seen that all three approaches gave the same optimum machining parameters, and hence the validity of the optimum machining parameters can be said to be reliable. The optimum combination of the parameters was found to be v_c = 150 m/min, v_f = 0.18 mm/rev, and a_p = 1.2 mm, giving the minimum RMS vibration value of 14.246 g and flank wear of 0.110 mm.