Potentiodynamic study of the influence of gamma prime and eta phases on pitting corrosion of A286 superalloy

Abstract

This work studies the influence of gamma prime and eta phases on the pitting corrosion of A286 superalloy by potentiodynamic anodic polarization (PAP) and cyclic potentiodynamic polarization (CPP). The general trend for pitting potential (Epit) parameter is that: (i) the higher the aging temperature, the lower the Epit; and (ii) Epit decreases with increasing aging time. The repassivation potential (Erp) allows to study the Epit–Erp difference, which decreases slightly with increasing aging time. The general trend for Epit is altered by the eta phase precipitation at GB which, although it may enhance pit initiation, grows at the expense of gamma prime phase. The general trend for and Epit–Erp is altered by the eta phase precipitation at GB because, even though the nickel-rich eta phase precipitation, just as gamma prime phase precipitation, causes the nickel content of the austenitic matrix to reduce and consequently the repassivation properties to increase, eta phase grows at the expense of gamma prime phase.