Due to specific requirements in NPP piping different materials are used and connected by dissimilar welds (DM). The fatigue behavior of such welds must be known for design and safety evaluations. The overall fatigue behavior of welds depends on the properties of the different weld sections and their interaction. The welding may influence the fatigue behavior of the base materials in the vicinity of the weld.
The investigation deals with the fatigue behavior of DM typical for German NPP: ferritic steel 20MnMoNi5-5 welded to austenitic steel X6CrNiNb18-10 using nickel based alloy for buttering. Fatigue specimens were taken from each region of the weld (ferritic steel near weld, buttering, connection weld, austenitic steel near weld). Additionally specimens were taken containing two adjacent material regions and the respective fusion line. For each position specimens were tested in fully reversed strain controlled conditions at room temperature and total strain amplitude of 0.25%. The results were compared with the best-fit curves for austenitic and ferritic steels.