Creep cavities and carbide evolution in interrupted creep conditions along P91 steel of dissimilar weld joint

The creep behaviour of dissimilar weld joint of 316LN SS-P91 steel when subjected to lower applied stresses (below 100 MPa) generally fails in a Type-IV pattern. The dissimilar weld joint was welded through shielded metal arc welding (SMAW) process with INCONEL as electrode, a nickel-based superalloy. An interrupted creep test was carried out at creep condition of 80 MPa −600 °C temperature. Interruption was done at two stages of creep, i.e. (a) mid of secondary and (b) start of tertiary. Microstructural evolution with respect to the hardness variation along various regions of P91 steel at interrupted and the failed specimen was done. A coarsening of hierarchical boundaries and M23C6 carbides was observed along HAZ region that has resulted with respect to time and temperature.