High-temperature fatigue behavior and cyclic deformation of a gradient nanostructured RAFM steel

•The gradient characteristics in the GNS surface layer was stable after annealing at 550 ℃ for 60 min due to the pinning effect of precipitates.•The introduction of GNS surface layer could significantly improve the high-temperature fatigue properties of CLAM steel.•The strengthening mechanism could be attributed to the synergistic effect of grain refinement strengthening, compressive residual stress arising, and strain delocalization caused by the formation of the GNS surface layer.