High-temperature crack growth behavior of high-chromium steels

High-chromium steels are widely used in recent fossil power plants because of their excellent high-temperature strength. They are also regarded as promising candidates for structural materials for high-temperature nuclear power plants such as liquid metal-cooled fast reactors and high-temperature gas-cooled reactors. Their crack growth property is often required to evaluate the structural integrity under the presence of detected or postulated flaws. In addition to fatigue crack growth property, crack growth property under creep and creep-fatigue loading is important because of high operating temperatures of these plants. As a study in the working group organized in Japan Society of Materials Science, experimental and analytical studies have been conducted on high-temperature crack growth property of representative high-chromium steels. Researchers from plant manufacturers, utilities and universities participated to this activity. Temperature- and specimen -dependency of crack growth properties in terms of J-integral type fracture mechanics parameters were examined in detail. Standard equations were derived to estimate crack growth rate as a functions of these parameters. Effect of constraint on creep crack growth behavior was found to be quite large. (authors)