Fatigue Behaviour of Stainless Steel Used for Turbine Runners

Abstract

Abstract. The key ingredient for any turbine runners design procedure and failure analysis is the material and its mechanical and fatigue properties. Starting from this observation, a series of static and dynamic tests were performed on the T10CuNiCr180 stainless steel after more than three decades of service. The fatigue tests were carried out under constant amplitude at a stress ratio of 0.1 and a frequency of 20 Hz. In the high cycle fatigue range, the S-N median curve was plotted and the fatigue limit for 3⋅10 6 cycles to failure was determined at 93.35 [MPa] expressed in stress amplitude. The casting and welding defects that were observed on fracture surfaces explained this lower fatigue limit. The fatigue crack growth tests were performed on compact tension specimens and a three-parameter model was used to plot the crack length versus number of cycles curves. In addition, the material constants from Paris' law were determined. Finally, the experimental results are compared against published data for another stainless steel.