Abstract
Dissimilar tungsten inert gas (TIG) welding of furnace tube alloys, T92, T91 and T22, using TG-S2CM, TG-S2CW and TG-S9Cb fillers is performed in the experiment. Post weld heat treatments (PWHTs) of specimens selected from wire cutting of the qualified weldments are carried out in order to evaluate carbon migration phenomena. The soft zone resulted from carbon migration can be evaluated by optical microscope and microhardness tests. Based on the long-term aging test results, obvious soft zone is found from the weldment with significant difference in alloying concentrations. There is no soft zone in T92/T91 dissimilar weldment using the TG-S9Cb filler after the aging test. In contrast, soft zones are observed from the interfaces, TG-S2CM/T92 and TG-S2CW/T92. The size of soft zone (~50 μm) using TG-S2CW filler is much less than that using TG-S2CM filler (~200 μm). The application of TG-S2CW filler shows potential in welding/repair welding of T92/T22 tubes in supercritical boilers.
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