A tungsten inert gas welded joint between a novel heat-resistant austenitic steel and ERNiCrCoMo-1 weld metal was investigated before and after creep in this study.The evolution of the microstructures in the base and weld metals was discussed based on the electron back-scatter diffraction (EBSD) and transmission electron microscopy (TEM) analyses.The preferred orientations of the fusion boundary after creep revealed the influence of the applied stress on creep deformation mechanism.A cooperative nucleation process of M23C6 carbides in the base metal was proposed.The finely distributed Cu-rich phase was cut off by the dislocations during creep,leading to increased mean size and reduced amount of the nano-Cu phase.A modified triple-precipitate hardening model was constructed based on TEM observations of the interactions between the particles and the dislocations in the base metal after creep at 200 MPa.The evolution of a μ phase in the weld metal involved epitaxial growth and dissolving into the matrix.