Effect of material heterogeneity and testing temperature on fatigue behaviour of Cr-Mo steel welded joints

•Provides insight into the change in fatigue behavior of steels at elevated temperatures.•A detailed analysis of welded joint heterogeneity, with experiments involving all three regions (PM, WM, HAZ)•Provides a base of reliable results that can be used in further analysis (e.g. XFEM) Successful application of Cr-Mo steel depends crucially on behaviour of all zones in welded joints, i.e. base metal (BM), heat-affected-zone (HAZ) and weld metal (WM), both at room and working temperature. Different amplitude loadings were applied for testing of specimens without a crack, made of welded joint as a whole and of BM, in order to obtain Woehler’s curves and compare their dynamic strength. Amplitude loading was also applied for testing of specimens cracked in BM, HAZ and WM, in order to get fatigue crack growth curves and parameters C and m in Paris law. Results are analysed to get deeper insight into behaviour of welded joints, made of steel SA 387 Gr. 91, under amplitude loading both for room and working temperature.