Creep Damage Detection of Steels

Abstract

Structural metals are subject to aging from fatigue, creep, corrosion, irradiation, and their combination. Exposure to high temperatures promotes creeping and stress-corrosion cracking. Aged metals lose toughness, or ability to absorb energy for stresses above the yield point. They cannot withstand the occasional high loads without fracturing. In-service degradation with creep is one of major concerns in power plants, chemical plants, and oil refineries, being an important issue of worldwide significance. For instance, many of fossil-power plants were constructed during 1960’s and 70’s and their working time have exceeded more than 100,000 h. They are still operating while they have undergone progressive damage, mainly from creep as the time proceeds. By shifting the base load of power from fossil-power plants to nuclear-power plants, they are facing even more severe operating conditions such as daily or weekly startup and shutdown in order to meet the rapid change of electricity demand. Furthermore, the steam pressure and temperature in boiler components are increasing to improve the thermal efficiency for energy saving and reduction of CO₂ emission. As the consequence, the material’s degradation is being accelerated.