High-chromium martensitic steels are one of the basic creep-resisting construction materials used for the modernization of old and the construction of new power units. During the service under creep conditions, the metastable microstructure of martensitic steels undergoes gradual degradation. The rate of degradation mostly depends on the operating temperature, but it is also affected by stresses. The changes in the microstructure of martensitic steels have an influence on the decrease in their mechanical properties, including creep resistance. The knowledge and description of the changes in the microstructure of steels working under creep conditions allow extending the time of safe operation of the elements of power systems. The paper presents and describes the main mechanisms of degradation of 9–12%Cr martensitic steels on the basis of the independent studies and literature data.
Part of the book: Creep