Fast Reactors and Accelerator Driven Systems Knowledge Base

Conference Article: Assessment of creep behaviour of austenitic stainless steel welds

Sasikala, G.; Mathew, M.D.; Bhanu Sankara Rao, K.; Mannan, S.L. (Indira Gandhi Centre for Atomic Research, Kalpakkam (India))

Abstract

The creep properties of a nitrogen alloyed type 316 L stainless steel (316LN SS) base metal and weld metal of nuclear grade were studied at 873 and 923 K in the range of applied stresses from 120 to 315 MPa. The results were compared with those obtained on a nuclear grade type 316 SS. Creep rupture lives of the weld metals were found to be lower than those of the respective base metals by a factor of 5 to 10. Both the base metal and the weld metal of 316LN SS exhibited better rupture lives compared to 316 SS base metal and weld metal respectively at identical test conditions. At 923 K, the stress exponent for minimum creep rate was about 9,5 for both the base metals, whereas it was about 12 for the weld metals. However, in the case of 316 SS, the weld metal exhibited higher creep rates compared to the base metal whereas for 316LN SS the creep rate of the weld metal was lower by a factor of 5 at high stress levels to 10 at lower stress levels, compared to that of its base metal. Both the weld metals exhibited lower rupture elongation compared to that of the respective base metals at 873 and 923 K. Comparison of rupture lives of the two steels with the ASME Code Case N-47 curves for the base and weld metals showed that in the case of 316 LN SS the specifications for maximum allowable stresses are over-conservative. The creep rupture results are rationalized on the basis of evolving microstructure.

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key words: Fast Neutron Spectrum Systems, Nuclear Technology
Reference:
Creep-fatigue damage rules for advanced fast reactor design. Technical committee meeting, Manchester (United Kingdom). 11-13 Jun 1996
International Atomic Energy Agency, Vienna (Austria)
IAEA-TECDOC--933, pp:219-227