Investigation of Joints Design Geometry Effects on the Microstructural Aspects and Corrosion Mechanism of Weld Metal in the Hadfield Steel Welding Joints

In this study, the effect of joints design geometry on the microstructural aspects and corrosion mechanism of weld metal in the Hadfield steel welding joints was investigated. For this purpose, initially 4 austenitized sheets of Hadfield steel with 2mm thickness prepared. Then joints design with two chamfered V and X forms were prepared and SMAW process was used for welding. In the next step, potentiodynamic polarization and electrochemical impedance spectroscopy methods were used to evaluate corrosion behavior of welded joints weld metal in the 3.5% NaCl solution. Also optical microscopy method was used to evaluate the microstructure of weld metal, Corrosion morphology of weld metal were investigated by scanning electron microscopy and X-ray diffraction was used for the analysis of phases formed in the microstructure if weld metal. The results indicated that with using joints design containing chamfered V-shape in comparison with joints design containing chamfered X-shape in the Hadfield steel welded joints, resulted microstructures consisted from smaller grains and more carbide precipitates. The results indicated that V-shaped chamfers in comparison with X-shaped chamfer led to reduction in corrosion resistance and changed weld metal corrosion mechanism from uniform corrosion to localized micro-galvanic corrosion in the Hadfield steel weld joints.