Study on solid-phase welding of duplex stainless steel with carbon steel based on superplasticity and consideration of the cyclic fatigue fracture behavior

In this study, we have attempted the solid-phase welding of superplastic duplex stainless steel (SPDSS) with carbon steel that has a carbon content of 0.43 wt% (S45C). The welding was performed at 1373 K. The ultimate tensile strength of the welded specimen increases with the welding time and becomes approximately the same as that of S45C for a welding time above 220 s. And the carbon contents of the interface between both materials change. The carbon content of S45C decreases, while that of SPDSS increases in the region near the interface. Considering from these result, the carbon in S45C diffuses into SPDSS. Then we have investigated cyclic fatigue fracture of the welded specimen. The crack initiates in the decarburized layer of the S45C section of the interface. When the crack propagates the interface, the crack extended drastically. Cyclic fatigue fracture property is similar to that of low carbon steel that has a carbon content of 0.1 wt%. On the basis of these results, we can conclude that SPDSS can be suitably used for solid-phase welding of carbon steel in a short-duration.