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, Cr 23 C 6 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 Cr 23 C 6 particles around cavity so as to maintain a considerable level of ductility. Furthermore, the defect accumulation in the form of dislocation wall around Cr 23 C 6 particle appears to be responsible for providing significant high-temperature strength so as to justify the success of the adopted joining route.