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Fig. 12.24. Photomicrographs of the fractures of Hastelloy N tube-burst samples exposed to steam at 538째C. (a) Stressed at 66,000 psi and failed in 4.0 hr, (b) stressed at 56,000 psi and failed in 27.4 hr, and (c) stressed at 55,300 psi and failed in 99.7 hr. As polished.