Avaliação de microestrutura e propriedades mecânicas de juntas obtidas pelo processo FTPW em aço inoxidável duplex

Abstract

The objective of this work was to characterize the microstructure and mechanical properties of duplex stainless steel welded joints produced by FTPW (Friction Tapered Plug Welding). In this study, it was used pipes made of duplex stainless steel UNS S32205. The pins used to fill the cavities were of the same material. The macro and microstructure were analyzed in longitudinal sections of the welds and the volumetric percentage of each phase was measured using quantitative metallography. The mechanical properties were evaluated by means of hardness, tensile and bending tests. The selected welding parameters produced joints without any significant defect. Along the welding interface between the added pin and the substrate, the microstructure was mainly ferrite and austenite of varying morphologies, such as intragranular, allotriomorphic, partial transformed, primary, secondary and Widmanstätten plates. At the thermo-mechanically processed interface a higher percentage of δ-ferrite as observed. The tensile tests did not show any significant variation of the mechanical properties (yield and tensile strength) along the weld joint depth. However, the hardness profiles showed higher hardness values at the thermo-mechanically processed interface. Despite of this, all specimens were bended by 180° without any crack formation.