EFFECTS OF MATERIAL COMPOSITION ON CORROSION FATIGUE CRACK GROWTH OF AUSTENITIC STAINLESS STEELS IN HIGH TEMPERATUREWATER

摘要

Laboratory studies on austenitic stainless steels in PWR primary coolant environments have shown that the ASME XI procedures used to assess fatigue crack growth of reactor components may not always be conservative. Recent work has shown that significant environmental enhancement of growth rates can occur in this environment, especially for some long rise time loading cycles. Although enhancements up to eighty times relative to air data have been observed, under some conditions retardation of the enhanced growth rates can also occur, leading to rates close to the ASME XI air line. Several factors appear to influence retardation, including temperature, water flow rate and material composition. The current study addresses the influence of material composition and it is shown that steels of high sulfur content (>0.02%) are much more prone to retardation than low sulfur (<0.01%) steels. Work aimed at elucidating possible mechanisms for this effect is described.