Analysis of cavity evolution in 9%Cr heat-resistant steel welded joint during creep

•The FGHAZ exhibits the most serious cavity damage in ASME T92 welded joint.•The cavity number density and cavity area fraction in the FGHAZ increase with increasing creep time.•The adjacent cavities grow and propagate into the cavity chain, and extends to the micro-crack.•The life of T92 steel welds can be correlated with cavity by using the fitting damage model.