Microstructures and mechanical properties of dissimilar T91/347H steel weldments

Shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW) and their combination are processed by using austenitic and nickel based diverse welding electrodes/filler wires to prepare the dissimilar weldments. The comparative evaluation of an appropriate welding process and welding consumable is based on microstructural features, micro-hardness variation, tensile testing and fracture morphology. The martensitic morphology is found responsible for the higher micro-hardness of HAZ of T91 side of all the weldments. Higher tensile strength (638.2 MPa) of GTAW, ERNiCr3 combination is observed than other weldments. The fractography corroborates the highest ductility of GTAW, ERNiCr3 combination with an elongation of 28.33% and the ductility of all the combinations of weldments except GTAW, ERNiCr3 is observed to be less than their base metals. Hence, it can be concluded that GTAW process, using nickel based weld metal offered the better results for the dissimilar joint between T91 and 347H.