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U.S. Department of Energy
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Embrittlement studies in austenitic stainless steels

Technical Report ·
OSTI ID:6958515
;  [1];  [2]
  1. Oregon Graduate Inst. of Science and Technology, Beaverton, OR (United States)
  2. Pacific Northwest Lab., Richland, WA (United States)

Potential causes for high strain rate induced embrittlement in Type 304 and 316 austenitic SSs have been classified as grain boundary carbide precipitation; grain boundary P segregation; grain boundary martensite formation; and sigma phase precipitation. The impact energy of heats containing a substantial amount of C decreases rapidly as a result of sensitization heat treatment. Temperatures below or above this result in very little embrittlement. Intergranular embrittlement can be produced solely by grain boundary carbide precipitation. Phosphorus played only a secondary role, if any, in the development of IG fracture. No formation of grain boundary a thermal martensite was observed; its presence at the grain boundaries is not required to cause a massive drop in impact toughness. Distribution and morphology of grain boundary carbide precipitates significantly affects the impact toughness of the steels. Carbides formed at high aging temperatures are coarser and the impact drop is not as pronounced as at lower temperatures. Precipitation of sigma from retained delta-ferrite takes place at very short aging times and severely degrade the impact toughness. A maximum of 10% P for 316 SS and 20% P for 304 SS (monolayer coverage) was observed at grain boundaries, not enough to cause embrittlement.

Research Organization:
Oregon Graduate Inst. of Science and Technology, Beaverton, OR (United States)
Sponsoring Organization:
DOE; USDOE, Washington, DC (United States)
DOE Contract Number:
AC06-86NE37963
OSTI ID:
6958515
Report Number(s):
DOE/NE/37963-21; ON: DE93005059
Country of Publication:
United States
Language:
English