Machining induced surface integrity behavior of nickel-based superalloy: Effect of lubricating environments

Abstract

Surface integrity is a critical aspect of machining nickel-based alloys due to their applications in critical components and employment in a harsh environment. The development of sustainable methods for machining difficult-to-cut materials is now of utmost importance because of global environmental concerns, strict policies, and diminishing natural resources. Consequently, different sustainable machining techniques have been developed and utilized for characterizing surface integrity. In the present study, the application of ultrasonically atomized cutting fluid (UAF) has been employed for machining nickel alloys, and its influence on the surface integrity has been evaluated. Moreover, the performance of UAF process has been compared with previously existing machining techniques. The experimental study includes measurement of microhardness, residual stresses, surface topography, chip morphologies, and microstructural changes. The sin2ψ−sin2ψ technique of X-ray diffraction (XRD) is utilized for evaluating residual stresses, whereas microstructural analysis is performed using electron back scattering diffraction (EBSD). It has been found that different lubrication techniques reduces the surface hardening phenomenon by restraining the plastic deformation. Tensile residual stresses have been achieved in dry machining and MQL processes, while flood cooling and UAF processes resulted in compressive residual stresses. MQL and UAF processes have been found to result in less misorientation and grain redistribution as compared to dry and flood cooling. Overall, the UAF process has been found to result in improved surface integrity which enhances the product life and performance.