Surface modification of structural material for nuclear applications by electron beam melting: enhancement of microstructural and corrosion properties of Inconel 617

Abstract

Inconel 617 is widely used in nuclear industry, due to its excellent elevated temperature mechanical and chemical properties. In this study, austenitic super alloy Inconel 617 has been subjected to electron beam surface melting using an indigenously developed electron beam welding unit (80 kV, 12 kW) for microstructural homogenization and understanding its effect on corrosion resistance property. Electron beam surface melting has been carried out at a gun voltage of 60 kV, current of 30 mA, and scan speed of 1000 mm/min inside a vacuum chamber with a vacuum level of 1.6 × 10 −5 mb. Surface melting induced by EBM led to development of refined microstructural features consisting of γ dendrites and precipitates of Ni 3 (Al, Ti) in the interdendritic regions, which further improved microhardness of the Electron Beam (EB) treated surface. The effect of electron beam melting on the kinetics of aqueous corrosion has been determined in acidic 3.56 wt% NaCl media. The improvement in corrosion resistance can be attributed to the microstructural refinement leading towards the redistribution and homogenization of alloying elements and surface purification.