Influence of W concentration on the Charpy impact property and corrosion behavior of reduced activation ferritic-martensitic steels for fusion reactor

•An increase in W content to 2 wt% in RAFM steel caused the formation of δ-ferrite.•W atoms were enriched in δ-ferrite, stabilizing it during normalizing and tempering.•δ-ferrite provided easy paths for crack propagation during the impact test.•δ-ferrite acted as pit initiation sites, deteriorating corrosion resistance.