Investigation on microstructure of weld metal of HR3C heat resistantsteel afterservice for 50000 hours

Abstract This paper studied the microstructure of the HR3C steel-welded metal having serviced for 500 hours via metalloscopy, scanning electron microscopy and Energy Disperse Spectroscopy (EDS). As the result shows, the HR3C steel-welded metal remains the cellular-dendrite structure after 500 hours of service, with the number of its precipitated phases increased and its size enlarged. The M23C6 carbide is distributed in the strip or lump pattern along the boundaries of afterbirth-like crystals and dendritic crystals, while it is distributed in the form of small particles close to the crystal boundaries. Cu-rich phase, NbCrN- and Nb (C, N) - precipitated phases are highly stable and small, which accounts for the main reason why the HR3C steel welding joint presents high intensity.