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.

The knowledge of residual stress arising from the welding processes is extremely important because the mechanical properties of the welded components are not only determined by the microstructures present in the joint, but also by the heterogeneous residual stresses introduced during the thermal cycle in welding processes. The aim of this work is the characterization of ASTM P91 steel-pipe welded by Metal Cored Arc Welding &Flux Cored Arc Welding (MCAW/FCAW) processes, through the residual stresses evaluation associated with welding and post-weld heat treatment (PWHT). Residual stresses were analysed by X-ray diffraction technique with sin2ψ method, presenting tensile behaviour with higher magnitude at the weld metal of root region. The PWHT promoted the relief of the residual stresses in the both regions. High Vickers microhardness values were observed in the weld metal region before the PWHT, which was very efficient to reduce them.