1990 Volume 30 Issue 7 Pages 540-545
Creep damage in pressure parts due to high temperature service is composed of metallurgical damage and mechanical damage. Mechanical damage such as cavitation and microcracks are easily detectable parameter for creep life assessment. On the other hand metallurgical damage resulting from structural degradation and fluctuation of alloy element in matrix and precipitates are difficult to detect quantitatively, in spite of a predominant factor to reduce creep strength and to induce integranular creep cavitation. Through the investigation into the long term used elevated temperature pressure parts removed from a power plant, a new materials-evaluation technique was developed, which is the quantitative analysis of the structural changes such as the alloy element fluctuation in matrix with precipitates in terms of creep damage percentage. Consequently, concentration spectra of alloy element in matrix with coarsening precipitates revealed by computer-aided X-ray microanalyzer (CMA) gave the significant structural parameter to determine the creep damage percentage.
