Characterization of Subsurface Microstructural Alterations Induced by Hard Turning of Inconel 718

Abstract

Conventional machining especially hard turning is commonly used in aerospace industry to produce the final shape of cylindrical parts. However, the process generates damages and microstructural alterations on the surface and at the subsurface layer, in particular the cracking of hard carbides particles. The present paper focuses on investigating the probable mechanisms responsible for carbide cracking and the formation of a softened layer at a depth between 10 and 30 µm below the machined surface. Advanced techniques, such as laser confocal microscopy and field emission gun scanning electron microscope equipped with in situ picoindenter and electron backscatter diffraction, were used to characterize and analyze the evolution of the microstructure in the affected layer and propose the possible governing mechanisms for the observations.