Microstructural and Mechanical Characterization of Artificially-Aged Power Plant Steel

Degradation of properties due to ageing at high temperature service is a common problem which normally occurs in electricity generation power plants, refineries, petrochemical industries. This work investigates the influence of accelerated artificial ageing on the microstructural and mechanical properties of 9-12%Cr steel usually used in power plants. This steel was tested in the as-produced and aged for 2, 5 and 8 weeks at 700°C. Results showed that the microstructural features such as phases, carbides, i.e. morphology and type, sub-grains and their boundaries and misorientation angles are the dominant factors influencing the mechanical properties. Ageing led carbides to go into solution in the martensite-ferrite structure and also led to the increase of average misorientation angle as well as to the reduction of low angle grain boundaries. In addition, ageing led to the reduction in the mechanical properties and hardness when compared to the as-produced condition.