An Investigation of Dissimilar Metal Weld Joints: SB166–Alloy 82/182–SA182

Abstract

The alloys 82 and 182 have been widely used as filler metal to join austenitic stainless steel with alloy 600 by a shielded metal arc welding process in the reactor pressure vessel and pressure vessel nozzles, which are both components in boiling water reactors. These components are affected by interdendritic/intergranular stress corrosion cracking, usually confined to the welding metal of alloys 82 and 182. For better understanding of this effect, the heat-affected zones (HAZ) were studied. Usually, the damages are present in dissimilar metal welds along the fusion lines; this zone is susceptible to cracking. This is an important reason to research the microstructural behavior in the transition regions. For this study, specimens for dissimilar welding SB166–Alloy 82/182–SA182 were prepared; the physical dimensions of the specimens were 2.0 by 1.0 by 0.375 in. (5.08 by 5.54 by 0.95\xa0cm). The welding metals were prepared as multilayer by shielded metal arc welding process using electrodes ERNiCr3 and ENiCrFe3. The microstructural characterization was realized by optical and scanning electron microscopy, including electron backscattering diffraction technique. Additionally, the Vickers microhardness profile was recorded using a Shimadzu Model HMV-G-20DT. The measurements were from the base metal and HAZ as well as the welding. The microscopy analysis shows that austenite phase is present in both base metals. The chemical compositions of different materials indicate that they correspond to the joints of alloy 600 and stainless steel (SS) 304L with alloy 82 and 182. The values of microhardness are interesting results of these joining welding. They show a slight increase in the hardness value as the measurements approached the fusion line, with the exception of the SA182 alloy.