Characterization of isothermally aged Grade 91 (9Cr-1Mo-Nb-V) steel by electron backscatter diffraction

An electron backscatter diffraction (EBSD) investigation on the effect of long-term aging on the microstructure of modified 9Cr-1Mo steel for steam piping in power plant has been carried out. EBSD has been used to determine changes in the matrix microstructure, such as the ratio of low to high angle boundaries and the total grain boundary length. Both have been shown to increase with increasing aging times at 650 °C. This paper discusses the suitability of EBSD for the assessment of recovery of the matrix microstructure of ferritic power plant steels.