SYMPOSIA PAPER Published: 01 January 2004

Evaluation of Irradiation Embrittlement of A508 Gr 4N and Comparison to Other Low-Alloy Steels


A508 Gr 4N has improved fracture toughness because of the addition of 3% nickel, compared to typical low-alloy steels which have less than 1% nickel. However, there is an expectation in much of the recent literature, based mostly on low-alloy steels with nickel below 1%, that irradiation embrittlement will increase with increasing nickel (Ni) content. In contrast, the raw irradiation test data show that ASTM A508 Grade 4N containing up to 3.7% nickel, 0.1% Cu and 0.01% P does not show enhanced irradiation embrittlement. Statistical analyses of the irradiation data were performed to enable more quantitative comparisons to other steels. The peak irradiation embrittlement of A508 Gr 4N is no greater than that of A508 Gr 2, a 0.7% Ni forging material tested under similar conditions with similar limits on Cu and P. At high dose (80 mdpa) the average embrittlement of A508 Gr 4N is slightly higher (about 33%) than the lower nickel materials A508 Gr 2, A533B and A302B with similar Cu and P. The irradiation temperature dependence of embrittlement in A508 Gr 4N is nearly the same as other low copper low-alloy steels tested over a wide range of temperatures. The shift in Charpy transition temperature (TTS) in A508 Gr 4N is due to radiation hardening, and the ratio of TTS to yield strength increase in 3 Ni steels is nearly identical to that observed for conventional low-alloy steels with lower nickel. Cu and P increased embrittlement in A508 Grade 4N steel, similar to that for A508 Gr 2 steels irradiated in surveillance tests.

Author Information

Wire, GL
Bechtel Bettis, Inc., West Mifflin, PA
Beggs, WJ
Bechtel Bettis, Inc., West Mifflin, PA
Leax, TR
Bechtel Bettis, Inc., West Mifflin, PA
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Developed by Committee: E10
Pages: 179–193
DOI: 10.1520/STP11227S
ISBN-EB: 978-0-8031-5494-0
ISBN-13: 978-0-8031-3477-5