Abstract
Austenitic-ferritic stainless steels are alloys with controlled additions of Cr, Ni, Mo and N which, after a suitable thermomechanical treatment, results in a balanced microstructure with similar proportions of ferrite (δ) and austenite (γ). Thus, it is possible to obtain good combinations of high mechanical properties and corrosion resistance through microstructural refinement, which also leads to a relatively good Pitting Resistance Equivalent value (PRE) at both phases. However, inadequate heat treatment and/or welding processes might result in the precipitation of deleterious phases, leading to poor mechanical properties and/or corrosion resistance. In this sense, the use of non-destructive microstructural characterization techniques becomes a valuable resource to access such alterations. Therefore, this work evaluates the precipitation of deleterious phase’s in welded thermal aged joints by portable Double Loop Electrochemical Polarization Reactivation (DL-EPR) taking into account a preliminary metallographic replica characterization. The results show that the proposed portable method can detect even a small percentage of deleterious phases, in addition to having a strong potential to be a non-destructive microstructural characterization technique.
Highlights
The duplex (DSS) and super duplex (SDSS) stainless steels, referred to as austenitic-ferritic stainless steels, are ferrous alloys that combine high mechanical strength and corrosion resistance[1]
The more sensitive solution test to detect deleterious phases in Double Loop Electrochemical Polarization Reactivation (DL-EPR) performed at room temperature was 2.5MH2SO4 + 0.02MKSCN + 0.77MNaCl for the DSS and 2.5MH2SO4 + 0.02MKSCN + 1.00MNaCl for the SDSS
In welded samples only a negligible reactivation peak was observed in the WJ2-welded condition (WC) region, because a high interpass temperature (T0) was employed in the welding procedure
Summary
The duplex (DSS) and super duplex (SDSS) stainless steels, referred to as austenitic-ferritic stainless steels, are ferrous alloys that combine high mechanical strength and corrosion resistance[1]. These properties are attained due to the fine biphasic microstructure composed of similar proportions of ferrite and austenite phases, and by the presence of Cr, Mo and N elements in solid solution[2], when other tertiary phases are not present. This work aims to access the efficiency of the portable Double Loop Electrochemical Polarization Reactivation (DL-EPR) method, assisted by metallographic replica, to detect deleterious phases in different thermal aged weld joints
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