Material characterization of 1Cr0.25Mo0.25V power plant steel after prolonged service

Abstract

Changes of mechanical properties and microstructure of specimens, which were taken from pipelines, made of heat resistant steel 1Cr0.25Mo0.25V after approximatelly 200000 hours of service at temperature of 540°C and stress 70MPa are considered in this paper. Also, the initial specimens, made of same steel that had not been at service were investigated. Results obtained by different experimental technique show that microstructural degradation had been dominant process during prolonged service in creep conditions, which lead to the changes of mechanical properties. Microstructural degradation and damages, like creep cavities and oxidation on internal surface of pipe, were observed. The changes of mechanical properties and significant decrease of hardness and micro hardness during service are explained by different processes that take place during microstructural degradation.