The element enrichment behavior during the aging treatment of PH13–8Mo steel and its influence on the evolution of microstructures and mechanical properties

The element enrichment behavior during the aging treatment of PH13–8Mo steel and its influence on the evolution of microstructure and mechanical properties were systematically investigated via scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), electron probe microanalysis (EPMA), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and atom probe tomography (APT). The results showed that a synergistic precipitation behavior between Ni and Cr exists during the aging process. This is mainly attributed to the element expulsion effect during the formation of reverted austenite (RA) and M 23 C 6 carbides as well as the enrichment effect of boundaries. The precipitation strengthening effect reaches its peak at 1 h and then continuously decreases as the nanoprecipitates coarsen, which is one of the main reasons for the strength evolution. Based on the systematic characterization of microstructures and the strengthening mechanism, the accurate prediction of the strength evolution process has been achieved, with an error of less than 30 MPa. RA is the key microstructure for impact toughness. The grain refinement and the transformation-induced plasticity (TRIP) effect stemming from RA are the main reasons for the improvement of toughness after peak aging.