| Abstract | Tribaloy alloy T-400C hardfacing deposited on Inconel 740H alloy via plasma transferred arc (PTA) welding has potential applications for high-temperature wear resistance of steam turbine components in the advanced ultra-supercritical (A-USC) operating condition. In this study, the T-400C hardfacing specimens via PTA welding are subjected to long-time (up to 25000 h) aging at the temperatures of 760 °C, 815 °C and 871 °C, which simulate the A-USC condition. The microstructures of the hardfacing layer, fusion zone and substrate before and after the long-time aging are studied with SEM, EDS and XRD, along with the hardness tests on the hardfacing layer to investigate the relationship between the hardness and the microstructural change of the hardfacing as a function of aging time. It is found that due to dilution occurring in the PTA process, the hardfacing has a hypoeutectic microstructure, which deviates from nominal T-400C alloy that is hypereutectic. Additional phases are generated in the hardfacing besides the Co solid solution and Laves phase. The long-time aging does not change the microstructures of the hardfacing and substrate in essence, but it can coarsen the Laves phase and promote formation of Ti-rich and Al-rich intermetallics in the hardfacing; coarsen the γ′ phase and change the carbides in the substrate. The new Ti-rich and Al-rich phases adversely influence the hardness of the hardfacing. |
|---|
