EFFECT OF FLOWING SODIUM AND PRIOR EXPOSURE TO SODIUM ON LCF AND CREEP-FATIGUE INTERACTION BEHAVIOR OF TYPE 316L(N) STAINLESS-STEEL

In order to assess the influence of liquid sodium, pre-ageing and hold time on low cycle fatigue behaviour of modified type 316 L(N) stainle ss steel studies have been conducted on as-received and sodium pre-exp osed (up to 3000 h) specimens at 823 K. The tests were conducted under continuous cycling and hold time conditions in sodium and in air envi ronments. The LCF tests were conducted under total axial strain-contro lled mode at a constant strain rate of 3x10(-3) s(-1), employing total strain ranges of 0.6%, 1% and 1.5%, and using a symmetrical triangula r wave form. Creep-fatigue interaction tests were conducted by imposin g tension holds of 10 and 30 minute durations at peak tensile strain. In general fatigue lives of specimens tested in sodium were found to b e higher than those tested in air up to by a factor of similar to 4. H owever, for tests conducted under hold time conditions, fatigue Lives in both the environments were comparable. Exposure in sodium prior to testing proved to be beneficial to fatigue life at all the three strai n ranges studied. This effect was more significant at low strain range s.