Study of influence of gamma prime and eta phases on corrosion behaviour of A286 superalloy by using electrochemical potentiokinetic techniques

摘要

This work studies the influence of gamma prime and eta phases, resulting from precipitation hardening, on the corrosion behaviour of A286 superalloy by using electrochemical potentiokinetic reactivation (EPR) and double loop electrochemical potentiokinetic reactivation (DLEPR). The general trend is that I_r, Q_r, I_r/I_a and Q_r/Q_a increase with aging temperature and, for a given aging temperature, with aging time, which is consistent with the fact that gamma prime precipitate may cause discontinuities in the passive layer. I_r, Q_r, I_r/I_a and Q_r/Q_a reach a peak, which alters the general trend, for both aging temperatures (670 and 720 ℃), at the aging time from which there is evidence of the presence of eta phase at grain boundary (GB). Gamma prime and eta precipitates can cause the passive layer that forms on them to become more unstable and, consequently, cause the current density through the passive layer and the susceptibility to localized corrosion attack to increase.