Microstructural Characterization of an Inconel 718 Alloy After Roller Burnishing Operations

Abstract

This article presents a broad microstructural characterization of an Inconel 718 alloy after a series of roller burnishing (RB) operations carried out at room temperature and at medium temperature (310°C), highlighting the deformed grain structure. To this end, several material characterization techniques were used, including optical microscopy, scanning electron microscopy, confocal microscopy, EBSD (electron backscattering diffraction) technique and nanoindentations. The results showed a wide variation and distribution of grains after deformation, and, in some cases, two important phenomena can be observed: the process of dynamic recrystallization in grains deformed at 310°C and the “strain-softening” phenomenon. The presence of the δ phase precipitated at grain boundaries is abundant in this alloy under all RB operating conditions. Grain deformation reaches an ideal size with just two RB passes. Above this number of passes, the asperities of Inconel 718 reach their deformation limit, and grain recovery phenomena and a slight reduction in hardness begin to be observed.