Comparative evaluation of LCF behavior of dissimilar steels and welds in an ultra-supercritical turbine rotor at 280 °C

摘要

Buttering layer (BL) was used to weld two ultra-supercritical turbine rotor steels. Low-cycle fatigue behavior of different regions in the dissimilar metal welded joint (DMWJ) was compared and evaluated at 280 °C. Microstructure, fracture and weak link were observed by OM, SEM, EDS and TEM. BL had lower fatigue life than weld metal (WM) and base metals (BMs). Weld zone showed cyclic softening characteristic. Microstructures evolved into cell structures after LCF tests. Fatigue crack in weld zone propagated mainly through coarse carbides. The interface near BL was the weakest link of the DMWJ due to ferrite layer and strength mismatch.