CORROSION OF WELDMENTS

Abstract

Austenitic Stainless steels like 304, 304L, 316L, AISI 201 stainless steel and 2205 duplex stainless steel (SS205) have been widely used in industries like nuclear, chemical, desalination and high pressure vessels etc. Typical uses also includes heat exchangers, furnace parts, jet engine parts, exhaust manifolds, tanks and parts exposed to marine atmosphere due to their high corrosion and oxidation resistance along with superordinate mechanical properties. The present study highlights the effect of welding parameters such as heat input and welding speedon the corrosion behaviour, microstructure and mechanical properties of weidments. The specimens were welded by GTAW (gas tungsten arc welding) process and the joints prepared were analysed for corrosion behaviour, microstructure and mechanical properties. The microstructure is investigated by using optical microscope,scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The microhardness test was performed using Vickers microhardness tester (Omnitech MVH- 11) and the tensile test is carried on 2.5KN 1-125K-S Tinius Olsen material testing machine. The corrosion behaviour was investigated in 3.5% NaCl solution using a potentiodynamic polarization test performed on gamry potentiostat. It was found that the specimen with joints made by using lower heat input result in higher corrosion potential, higher hardness and higher tensile strength & elongation as compared with those welded with higher heat input. The weld zone made using lower heat input results in reduction of the dendritic length and inter-dendritic spacing which was the main reason behind the observable variation in corrosion behaviour, hardness and tensile strength of welded joints.