Control of precipitation behavior in reduced activation steels by intermediate heat treatment

A special intermediate heat treatment was studied in order to obtain dispersed distribution of fine M23C6 carbides in reduced activation steels. The results indicated that MX carbonitrides rather than M23C6 precipitated first in the steel with intermediate heat treatment at 850 °C, which led to a decrease of carbon concentration in the supersaturated martensitic matrix and correspondingly a reduced volume fraction from 2.6% to 0.6% and mean size of M23C6 from 150 nm to 70 nm. The dispersed fine carbides were beneficial to the enhancement of the hardness in the steel. The intermediate heat treatment was proposed for an improvement of creep properties in reduced activation steel.