An assessment of material property degradation is carried out in this paper for an aged material taken from turbine component subjected to high temperature. Microstructure and chemical composition analysis is conducted to evaluate the damage status of the material after 16-year term of service. Testing samples are taken from the different regions of a steam turbine rotor with different working conditions. Regular material properties tests at high temperature, creep strength tests and creep crack growth (CCG) tests are performed to investigate the material property degradation. Experimental results reveal that the damage micromechanism is sensitive to temperature and stress state. High temperature tensile properties of the rotor steel materials are degraded due to the damage. The creep deformation rate and creep crack growth rate are higher in more degraded material than that in less degraded material. The relationships between the microstructure, internal damage evolution and the material properties are discussed for the aged rotor steel. This study will provide a further support for prediction of the residual life of the component with different degree of material degradation and creep damage.

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