A high N and W heat-resistant martensitic cast steel with balanced tensile strength and creep resistance achieved by Laves and μ intermetallics.

In this work, we developed a 9 wt% Cr martensitic heat-resistant cast steel with high N and W contents that achieved an excellent high-temperature strength and ductility balance at 923 K, i.e. the ultimate tensile strength and elongation for the steel are ~ 409 MPa and ~ 30.2%, respectively. Meanwhile, it exhibited the encouraging short-term creep performance at 923 K, like, 2425 h for 140 MPa, and 986 h for 155 MPa. Furthermore, the contribution of a mixture matrix including 10.3 vol% δ-Fe and lath martensite remaining to the excellent combination of properties was clarified as related to the W-rich precipitates, which is consisting of 1.7 wt% Laves phase (Fe2W), 0.9 wt% μ phase (Fe7W6). In detail, for the martensite, due to the energy-consuming transformation from μ to Laves, the coarsening rate of martensitic lath decreases as the decreasing ripening rate of Laves, realizing the strengthening. While, the δ-Fe strengthened by a high concentration of fine Laves with needle and rectangle morphologies deformed synergistically with lath martensite, improving the high temperature performance of the steel. The results from the study will provide new insights into the development of high performance martensitic heat-resistant steels. [ABSTRACT FROM AUTHOR]