Abstract
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.
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