Fusion Welding of T23 and T91 Steel Joints for Advanced Thermal Power Plant Application

The unresolved decisive aspect of joining T23 steel to T91 steel in a supercritical boiler is hereby taken up with reasonable success by adopting a cost-effective GTAW process with an iron-based filler wire (ER90S-B9). Quite a reasonable joint strength (UTS = 319 MPa) coupled with a considerable ductility (%elongation = 8) is ascertained by carrying out tensile test at boiler operation temperature (571 °C), known as one of the most critical tasks; and subsequently performing advanced characterization keeping all the significant regions of the weldment intact. Being pushed along with grain boundary sliding, Cr23C6 particles are clustered around the cavity evolved therein under tensile load applied at the boiler service temperature. The dimples originated through microvoid coalescence in the soft α-ferrite matrix eventually negate the cleavage mode of failure initiated at the segregated Cr23C6 particles around cavity so as to maintain a considerable level of ductility. Furthermore, the defect accumulation in the form of dislocation wall around Cr23C6 particle appears to be responsible for providing significant high-temperature strength so as to justify the success of the adopted joining route.