The critical aspect of joining T23 steel to T91 steel in a supercritical boiler is studied by a low-cost gas tungsten arc welding (GTAW) process using an iron-based filler wire (ER90S-G). The hardness variation across the weldment does not reflect any drastic fall in hardness, thereby indicating an absence of “soft zone.” A significant joint strength (UTS = 318 MPa) together with a modest ductility (%Elongation = 6) is established by carrying out tensile test at boiler operation temperature (571 °C) and thereafter carrying out advanced characterization keeping all different regions of the weldment intact. During high-temperature tensile deformation, Cr₂₃C₆ particles are found to be pushed along with grain boundary sliding and finally are clustered around the cavity formed thereby. The presence of Cr₂₃C₆ particles surrounding cavity promotes a cleavage mode of failure so as to negate a high ductility to be achieved. Yet, a modest ductility is still retained by virtue of soft α-ferrite matrix promoting a concomitant dimple mode of failure. Furthermore, these Cr₂₃C₆ particles are also found to be responsible for an accumulation of dislocation loops around them, thereby providing quite significant high-temperature strength with 88% joint efficiency.

中文翻译：

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T23-T91 异种钢在超临界锅炉中通过经济高效的熔焊工艺连接的实验分析

通过使用铁基填充焊丝 (ER90S-G) 的低成本气体钨极电弧焊 (GTAW) 工艺研究了在超临界锅炉中将 T23 钢连接到 T91 钢的关键方面。整个焊件的硬度变化并不反映硬度的任何急剧下降，因此表明不存在“软区”。通过在锅炉运行温度 (571 °C) 下进行拉伸试验，建立了显着的接头强度 (UTS = 318 MPa) 和适度的延展性 (%Elongation = 6)，然后进行高级表征，保持焊件的所有不同区域完整。高温拉伸变形时，Cr ₂₃ C ₆发现颗粒随着晶界滑动而被推动，并最终聚集在由此形成的空腔周围。围绕空腔的 Cr ₂₃ C ₆颗粒的存在促进了断裂的解理模式，从而否定了要实现的高延展性。然而，由于软的 α-铁素体基体促进了伴随的凹坑失效模式，仍然保留了适度的延展性。此外，还发现这些 Cr ₂₃ C ₆颗粒是造成位错环在它们周围积累的原因，从而以 88% 的接头效率提供非常显着的高温强度。