Microstructure and Mechanical Properties of Dissimilar Ferritic and Austenitic Steel Joints with an Intermediate Inconel-182 Buttering Layer

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Abstract
In this study, microstructure and mechanical properties of dissimilar weld joints between 2.25Cr-1Mo ferritic steel and 316L austenitic stainless steel, with and without an Inconel-182 buttering layer, have been investigated. The buttering layer widths produced on the machined edges of the ferritic steel plate were 3 and 5 mm. The dissimilar weld joints were butt-welded using a SMAW process with Inconel-182 electrodes. The results indicate that the ferritic base metal dilution effects are minimized due to buttering and a more uniform distribution of Fe, Ni, Cr and Nb contents is established over a broad region within the fusion zone. Moreover, a microstructure consisting of combined columnar and equiaxed dendrite with interdendritic Nb-rich particles is developed within the fusion zone as a result of buttering. Mechanical tests show that the average hardness, tensile ductility and impact energy of the weld metal were enhanced with increasing width of the buttering, while tensile strength properties were unaffected. It is observed that fracture surfaces of tensile specimens exhibit ductile features composed of ductile tear ridges with numerous interspersed dimples. However, the dominant fracture mode is noted to change from interdendritic to transdendritic with the use of a buttering layer.

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