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Effect of cutting parameter and cutting environment on surface integrity during machining of Nimonic C-263a Ni based superalloy

Machining of Nimonic C-263 has always been a challenge task owing to its hot strength, low thermal conductivity, tendency to work harden and affinity towards tool material. Topographical, mechanical, metallurgical, chemical and thermal changes happen in the surface and sub-surface layer of material during machining which influences the functional performance of component. The current research work investigated the influence of PVD multilayer coating and cutting fluid in the form of MQL and flood on surface integrity at different cutting parameter during machining of Nimonic C-263. Surface and sub-surface alteration such as surface damages, grain refinement, microstructural alteration, white layer and work-hardened layer during machining was examined using Surface roughness tester, Field emission scanning electron microscopy (FESEM), X ray diffraction (XRD) system, XRD texture measurement and micro hardness tester. Minimum quantity lubrication (MQL) and flood environment gives better surface quality by reducing cutting temperature and pressure during machining at low and medium cutting speed and feed. At high cutting speed and feed, high tool wear of uncoated tool and less cooling and lubricating efficiency of MQL and flood together deteriorate surface integrity of component by producing high thickness of white layer, high tensile residual stress, high work hardened layer, micro cracks, deformed grain boundary and grain refinement. Overall surface damages could not be reduced by using PVD coated tool under dry machining compare to uncoated tool under wet machining. It is interesting to note that the performance of PVD multilayer coated tool even under dry condition is comparable and sometime even superiorto uncoated tool under flood and MQL environment. The achieved results can be useful in guiding the selection of cutting conditions for acceptable surface integrity of machined component.