Effect of Pre-Strain and Aging Heat Treatment on the Corrosion Behavior for 2205 Duplex Stainless Steel in 6% FeCl3 Solution

Abstract

A 2205 duplex stainless steel (DSS) was pre-stretched to 5% and subsequently aged at 850 °C for 0–120 minutes, to explore the effects of pre-strain and aging treatment on the corrosion behavior of the DSS in 6% FeCl3 solution at 50 °C for 72 hours. The microstructure, hardness and corrosion behavior of the pre-strained and aged DSS were investigated based on statistical data and physical metallurgy in comparison with the counterparts without pre-strain. The results showed that the sigma (σ) phase precipitated firstly in δ-ferrite grain boundaries and then in δ-ferrite/γ-austenite (δ/γ) phases boundaries by consuming the volume fraction of δ-ferrite. The volume fraction of σ phase in the DSS with and without pre-strain increased with increasing aging times following a classical Johnson-Mehl-Avrami (JMA) relationship, and the kinetics of the precipitation of σ phase was accelerated by pre-strain throughout the aging time of 60–120 min. The hardness of the non-pre-strained DSS (NP-DSS) was lower than that of pre-strained DSS (P-DSS) throughout 0–120 min at 850 °C. The hardness of NP-DSS increased continuously with increasing aging time, and the hardness of P-DSS decreased firstly and then increased continuously with increasing aging time. The aged NP-DSS displayed a gradually serious pitting with increasing aging time, and the corresponding corrosion behavior of the aged P-DSS exhibited pitting firstly and then mainly cracking, and the pitting occurred in the vicinity of δ/σ and γ/σ boundaries.