Micrograin structure evolution associated with grain boundary characteristics in grade 91 steel during long-term creep exposure

Micrograin structure evolution in ASME Grade 91 steel after 233,823 h of creep exposure at 600 °C was characterized after grain boundary classification in terms of misorientation angle (MOA), boundary energy, and lath martensite substructure. Under long-term creep with an applied stress of 5.9 MPa, micrograin coarsening occurs by annihilation of lath boundaries, consisting of hexagonal dislocation networks (HDN), thanks to the “knitting-out” of...