Microstructure evolution in steel boiler tubes: A search for failure modes and deformation mechanisms

Life extension of power plants has become increasingly important due to the fact that many are reaching the end of their design life. Productivity and personnel safety concerns have forced many utilities that are considering plant life extension to establish programs to determine the extent of degradation of key components. The purpose of this investigation is to help develop a simple diagnostic technique that uses X-ray diffraction to predict the remaining life of such components or the earliest stages of incipient failure. In this study we have examined two burst boiler tubes using optical microscopy, transmission electron microscopy, Vickers microhardness measurements and X-ray diffraction. The aim is to understand the deformation process (or presumably related phenomena) using these different techniques and then to try to recognize it using X-rays in an effort to predict the remaining life.