Characterization of high temperature tensile and creep–fatigue properties of Alloy 800H for intermediate heat exchanger components of (V)HTRs

•High temperature tensile, creep–fatigue (C–F) properties of Alloy 800H are studied.•Strength and uniform elongation properties at 800°C are much lower than RT values.•Strong influence of hold time and Δɛtot on low cycle fatigue life was observed.•The total allowable C–F damage (D) at 800°C decreases with the decreasing Δɛtot.•Synergetic effect of C–F interactions showed stronger effect at lower Δɛtot values.