Abstract
The thermal strength properties of a non-quenched and tempered steel, MFT8 were investigated by stress rupture tests at 450°C. High-temperature tensile tests were also carried out to determine the stress range for the accelerated creep experiments. Optical microscope (OM) and scanning electron microscope (SEM) were used to analyze the fractography and microstructure evolution. The results showed that MFT8 steels exhibited transgranular fracture and high ductility in the stress rupture tests. Although the creep cavities were observed, the critical reason of creep rupture was the wedge cracks caused by stress concentration in the area of carbide fragments. The rupture life of MFT8 at 450°C/ 100000 hours was calculated to be 184.4MPa by linear extrapolation. The data of this study inferred that MFT8 had the potential to substitute for the quenched and tempered steels of the same class in power industry.
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