Microstructural evolution in Grade 91(9CR-1MoVNb) power plant steels

The aim of this research project was to gam a complete, quantified, understanding of microstructural changes in high Cr ferritic-martensitic power plant steels, as a function of preservice heat treatment, stress, time and temperature. The creep strength, which is the main design criteria for this class of alloys, depends on the stability of the microstructure, which consists of tempered martensite and a fine dispersion of carbide precipitates. An understanding of the changes of these two features forms an essential process towards the creation of a physically or microstructural-based model, which may improve the current approaches towards the prediction of remanent operational lifetime of these materials in service in conventional fossil-fired power plant... cont'd.