Microstructural and electrochemical characterization of friction stir welded duplex stainless steels

Abstract

Duplex stainless steels exhibit good mechanical properties and corrosion resistance as well as better weldability and lower sensitivity to the weld cracking. The friction stir welding is based on a tool to generate heat and deformation. This process has been studied to applications in oil/gas pipes, aerospace industry and equipments. In this work, the corrosion resistance of two friction stir welded (FSWed) samples (UNS S32205 and lean duplex UNS S32101) was evaluated using electrochemical impedance spectroscopy and the results were fitted to electric equivalent circuits. The electrochemical results indicate the presence of a high stability oxide of both duplex stainless steels not only at the base metal but also at the stir zone of the friction stir welded samples. All Bode phase diagrams presented two peaks associated to the oxide layer formed on the surface of stainless steels and the charge transfer. The corrosion resistance of the UNS S32205 was improved and the lean duplex UNS S32101 was decreased after friction stir welding process (FSW). Nevertheless, the resistance of the UNS S32101 FSWed was still similar or higher than the traditional austenitic stainless steels.