Effect of oxide layer on the electrochemical corrosion behavior of a Ni-based superalloy in 3.5 wt% NaCl

Abstract

The recycle technology of superalloy is a research hotspot and difficulty in the filed of superalloy. Recovery of superalloy bulk material is a major focus. Purification smelting after surface impurity removal is an application trend of superalloy regeneration technology. During the use and processing of superalloy, the surface will form a dense oxide layer. The oxide layer of superalloy scrap is difficult to remove by traditional mechanical method. However, the oxide layer on the superalloy surface can be efficiently removed by electrochemical dissolution. Based on the background above, we investigated the electrochemical corrosion behavior of GH4738 superalloy which oxidized for different time in 3.5 wt% NaCl. The effect of oxide layer on the electrochemical corrosion behavior of GH4738 was studied by potentiodynamic polarization and electrochemical impendence spectroscopy(EIS). The morphology and phase composition of the alloy were analyzed by scanning electron microscope (SEM), electron probe X-ray Micro-Analyzer (EPMA) and X-ray diffraction (XRD). The results indicated that the dense oxide film not only has a protective effect on the oxidation corrosion of the alloy, but also has a protective effect on the electrochemical corrosion of the alloy. The oxide layer impedes the electrochemical dissolution of the alloy.