Formation and evolution of layered structure in dissimilar welded joints between ferritic-martensitic steel and 316L stainless steel with fillers

Guoliang Liu^1,2，Shanwu Yang¹，Jianwen Ding¹，Wentuo Han²，Lujun Zhou¹，Mengqi Zhang^1,2，R.D.K.Misra⁴，Farong Wan²，Chengjia Shang¹

1. Collaborative Innovation Center of Steel Technology,University of Science and Technology Beijing2. School of Materials Science and Engineering,University of Science and Technology Beijing4. Laboratory for Excellence in Advanced Steel Research,Department of Metallurgical,Materials and Biological Engineering,University of Texas El Paso

摘 要：Dissimilar high-energy beam（HEB） welding is necessary in many industrial applications.Different composition of heat-affected zone（HAZ） and weld metal（WM） lead to variation in mechanical properties within the dissimilar joint,which determines the performance of the welded structure.In the present study,appropriate filler material was used during electron beam welding（EBW） to obtain a reliable dissimilar joint between reduced-activation ferritic-martensitic（RAFM） steel and 316L austenitic stainless steel.It was observed that the layered structure occurred in the weld metal with 310S filler（310S-WM）,which had the inferior resistance to thermal disturbance,leading to severe hardening of 310S-WM after one-step tempering treatment.To further ameliorate the joint inhomogeneity,two-step heat treatment processes were imposed to the joints and optimized.δ-ferrite in the layered structure transformed intoγ-phase in the first-step normalizing and remained stable during cooling.In the second-step of tempering,tempered martensite was obtained in the HAZ of the RAFM steel,while the microstructure of 310S-WM was not affected.Thus,the optimized properties for HAZ and 310S-WM in dissimilar welded joint was both obtained by a two-step heat treatment.The creep failure position of two dissimilar joints both occurred in CLAM-BM.

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