Abstract
In this study, heat treatment was carried out on modified 9Cr-1Mo steel specimens to determine the microstructural evolution for various normalizing temperature/time and tempering temperature/time combinations. Normalization was carried out in the temperature range of 1020–1100°C and time range of 2–8 hours, while tempering was performed in the temperature range of 690–790°C and time range of 2–20 hours. Optical microscopy was then used to visualize and chronicle the microstructural characteristics at varying levels of heat treatment. Vickers micro-hardness measurements were performed on each sample to obtain hardness values as a function of normalizing and tempering temperature/time. Creep tests have also been performed on as-received and welded specimens of modified 9Cr-1Mo steel, in the temperature range of 500–700°C and stress range of 50–200 MPa. Microstructural analysis was carried out on the specimens before and after creep deformation using both scanning and transmission electron microscopy. The microstructural evolution during the heat treatment and creep tests provided useful information to understand and characterize the creep deformation mechanisms of modified 9Cr-1Mo steel.