Abstract
The microstructures and the creep rupture properties of dissimilar welds between the Ni-based superalloy Inconel 740H and the non-stabilized austenitic stainless steel TP316H have been characterized. The welds were produced by shielded metal arc (SMA) welding process with the AWS A5.11 Class ENiCrFe-3 filler metal, commonly known as Inconel 182 superalloy. Postweld heat treatment at 760 °C for 4 hours was conducted to form γΠstrengthener in Inconel 740H. The austenitic weld metal produced by Inconel 182 had a dendritic microstructure, and grew epitaxially from the both sides of Inconel 740H and TP316H base metals. Since both Inconel 740H and TP316H did not undergo any solid-state transformation during welding process, there were no heat-affected-zone (HAZ) sub-regions and the coarsoned grains near the weld interface were limited to a narrow region. The hardness of Inconel 182 weld metal was ~220 Hv. The gradual hardness decrease was detected at HAZ of TP316H, and the TP316H base metal displayed the lowest hardness value (~180 Hv) whilst the Inconel 740H showed the highest hardness value (~400 Hv). Fracture after creep occurred at the center of weld metal, regardless of creep condition. It was found that during creep the cracks initiated and propagated along interdendritic regions and grain boundaries at which Laves particles enriched in Nb, Si and Cr were present. The appropriate design of weld metal was discussed to suppress the creep-induced cracking of the present dissimilar weld. Key words: Superalloy, Stainless steel, Dissimilar weld, Microstructure, Creep
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