Effect of Pulsed Current on the Microstructure, Mechanical Properties and Corrosion Behavior of Ni-Based Alloy/Super Duplex Stainless Steel Dissimilar Welds

Abstract

This work addressed the effect of pulsed current (PC) and pass number on the microstructure, mechanical properties and corrosion behavior of Incoloy 825/UNS S32750 welds. The alloys were welded using PC and continuous current techniques. Mechanical properties of the weldments were examined using hardness, Charpy and transverse tensile tests. General corrosion and pitting corrosion behavior of the weld metals were studied using potentiodynamic polarization and electrochemical impedance spectroscopy tests. The weld metals had a dual-phase microstructure including ferrite and austenite phases. Employing the PC mode resulted in an increase in the ferrite content of the weld metals, which led to the improvement in impact resistance. Based on the results of tensile tests, the weakest part of the weldments was Incoloy 825 base. The weld metals at the root pass showed the weakest corrosion behavior. Overall, use of the PC mode improved the properties of the weldments.