Mechanical properties of 9Cr-1Mo steel at ambient temperature after thermal holding at elevated temperature

The influence of thermal holding at elevated temperature 620degreesC for times from 100 up to 5000 hours on mechanical properties of the 9Cr-1Mo steel at ambient temperature was investigated. The structural changes in experimental material due to secondary phase particles precipitation during thermal holding after primary heat treatment (austenizing, quenching and high-temperature tempering) occured. The presence of secondary phase particles of M23C6, MX and Laves' phase (FeMO2) in microstructure of the experimental steel by means of TEM/EDX analyses was confirmed. The changes in microstructure of the 9Cr-1Mo steel during ageing can influence its mechanical properties at ambient temperature and change failure mode of the steel.