Carbide dissolution and precipitation in cold-rolled type 347H austenitic heat-resistant steel

Cold-rolled (CR) type 347H austenitic heat-resistant steel is investigated in this study, and the main strengthening phase, NbC, experiences the procedures of dissolution and precipitation twice, with the increase of deformation degree from 30% to 90%. Most of the primary NbC particles, remained during the solution treatment, dissolve in the austenitic matrix when the deformation degree is 30%, and rod-like NbC generates along the prior austenite grain boundary. Further deformation leads to the fragmentation and decomposition of the rod-like NbC. Until the cold rolling reduction reaches 90%, the dissolved NbC secondarily precipitates into nanoparticles and disperses throughout the martensite induced by deformation. The tensile strength of the 90% cold-deformed specimen, 1418 MPa, is enhanced by three times in contrast with the undeformed one.