Effect of Microstructure on Low Temperature Cracking Behavior of EN82H Welds

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As-fabricated EN82H welds are susceptible to low temperature embrittlements in 54 degree C hydrogenated water. Values of J[sub]IC in water are typically 90% to 98% lower than those in air due to a fracture mechanism transition from microvoid coalescence to hydrogen-included intergranular fracture. Environmental J[sub]IC testing demonstrated that a high temperature (1093 degree C) anneal and furnace-cool alleviates the material's susceptibility to hydrogen-induced intergranular cracking. To identify metallurgical and compositional features that are responsible for the material's environment-sensitive behavior, detailed characterization of the microstructure and grain boundary chemistry for the as-fabricated and as-annealed materials was performed. Results from light optical ... continued below

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Mills, W. J.; Brown, C. M. & Burke, M. G. April 30, 2001.

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  • Bettis Atomic Power Laboratory
    Publisher Info: Bettis Atomic Power Lab., West Mifflin, PA (United States)
    Place of Publication: West Mifflin, Pennsylvania

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As-fabricated EN82H welds are susceptible to low temperature embrittlements in 54 degree C hydrogenated water. Values of J[sub]IC in water are typically 90% to 98% lower than those in air due to a fracture mechanism transition from microvoid coalescence to hydrogen-included intergranular fracture. Environmental J[sub]IC testing demonstrated that a high temperature (1093 degree C) anneal and furnace-cool alleviates the material's susceptibility to hydrogen-induced intergranular cracking. To identify metallurgical and compositional features that are responsible for the material's environment-sensitive behavior, detailed characterization of the microstructure and grain boundary chemistry for the as-fabricated and as-annealed materials was performed. Results from light optical microscopy, analytical electron microscopy, electron probe microanalysis, Auger electron spectroscopy and mechanical property characterization are used to provide insight into the observed low temperature embrittlement phenomenon. The key microstructural feature responsible for low temperature cracking in as-fabricated welds appears to be fine niobium and titanium-rich carbonitrides that cover most grain boundaries. These precipitates are effective hydrogen traps that promote hydrogen-induced intergranular cracking. Dissolution the fine carbonitrides during the 1093 degree C anneal reduces grain boundary trapping sites, which accounts for the improved fracture resistance displayed by the annealed weld. The role of strength level in promoting low temperature embrittlement is evaluated by cold-rolling the annealed weld to increase its yield strength from 280 to 640 MPa. The annealed and cold-rolled weld exhibits high toughness in 54 degree C water and shows no evidence of hydrogen-induced intergranular cracking, thereby demonstrating that strength is not a primary cause of low temperature embrittlement.

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OSTI as DE00799220

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  • 10th International Conference on Environmental Degradation of Materials in Nuclear Power Systems-Water Reactors, Lake Tahoe, NV (US), 08/06/2001

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  • Report No.: B-T-3337
  • Grant Number: AC11-98PN38206
  • Office of Scientific & Technical Information Report Number: 799220
  • Archival Resource Key: ark:/67531/metadc743026

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  • April 30, 2001

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  • Oct. 19, 2015, 7:39 p.m.

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  • March 21, 2016, 12:52 p.m.

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Mills, W. J.; Brown, C. M. & Burke, M. G. Effect of Microstructure on Low Temperature Cracking Behavior of EN82H Welds, article, April 30, 2001; West Mifflin, Pennsylvania. (digital.library.unt.edu/ark:/67531/metadc743026/: accessed October 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.