High-Temperature Intergranular Crack Growth in Martensitic 2-1/4 Cr1Mo Steel,
ATOMIC ENERGY RESEARCH ESTABLISHMENT HARWELL (ENGLAND)
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Micromechanisms of high-temperature crack growth in martensitic 2 14cr-lMo steel have been studied in vacuum, under static loading at 500 C. Detailed metallographic and fractographic measurements have been combined with Scanning Auger Microscopy and crack growth resistance curves to characterize the micro-mechanisms of failure. At low stress intensities, the mode of crack growth is high-temperature brittle intergranular fracture HTBIGF and is controlled by the dynamic segregation of sulphur to crack-tip regions. Crack advance appears to occur by discrete jumps when a critical concentration of sulphur is achieved over the jump-distance. At high stress intensities, the mode of fracture changes to intergranular microvoid coalescence IGMVC, and is controlled by the distribution of sulphides. Of crucial importance are the relatively fine sulphides that reprecipitate from solid solution during the austenitising treatment.
- Properties of Metals and Alloys