The influence of precipitated austenite on hydrogen embrittlement in 5.5Ni steel |
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Authors: | Y -H Kim H J Kim J W Morris |
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Affiliation: | (1) T.J. Watson Research Center, IBM, P.O. Box 218, 10598 Yorktown Heights, NY;(2) Welding Research Institute, Hyundai Heavy Ind. Co., Ltd., 1, Cheonha-dong, Ulsan, Korea;(3) University of California, Berkeley, 278 Hearst Mining Building, 94720 Berkeley, CA |
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Abstract: | This work was undertaken to test the influence of precipitated austenite on transgranular hydrogen embrittlement in 5.5Ni
steel. Prior work has shown that the mechanism of transgranular hydrogen embrittlement in this steel is interlath separation.
Since the austenite that forms during the tempering of 5.5Ni steel precipitates on the martenite lath boundaries, it was hypothesized
that the austenite might have a beneficial effect. The experimental results show, however, that the precipitated austenite
decreases the toughness in the presence of hydrogen. The apparent mechanism is straightforward. The precipitated austenite
transforms to martensite in the strain field ahead of the crack tip. Interlath cracks appear at the periphery of the fresh
martensite particles. They are apparently caused by the volume change that accompanies the martensite transformation, which
imposes a tension across the lath boundary. The interlath cracks link together to form the macroscopic fracture. |
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