Microstructure and mechanical properties of dissimilar materials joints between T92 martensitic and S304H austenitic steels

In this paper, T92 martensitic steel and S304H austenitic steel were welded by gas tungsten arc welding (GTAW) process. Microstructural features and mechanical properties of T92 and S304H dissimilar materials joints were investigated. The results showed that the part of the joints with relatively weak tensile strength was T92 coarse-grained heat affected zone (CGHAZ), while the part of the joints which revealed relatively weak toughness was weld metal. The decrease of tensile strength in T92 CGHAZ was due to its coarse tempered martensite structure. Weak toughness of the joints was resulted from the coarse dendritic austenite of the weld metal. However, the weld metal in transverse direction of the joints was provided higher tensile strength by the orientation distribution of grains compared with T92 CGHAZ.

Research highlights
► Firstly reporting the welding between T92 martensitic and S304H austenitic steels.
► EBSD is firstly used to study the grain structure development of T92/S304H joints.
► Tensile property of T92/S304H joints is decided by microstructure of T92 CGHAZ.
► Impact toughness of T92/S304H joints is decided by grain size of weld metal part.