Precipitation kinetics of carbides during cyclical and isothermal aging of 2.25Cr-1Mo steel and its effect on mechanical properties

The carbide precipitation was analyzed during aging of 2.25Cr-1Mo steel at 550 degrees C. The as-received steel was aged in two different manners: the first treatment was an isothermal aging at 550 degrees C for time up to 1000 h, and the second one was carried out by a cyclical aging, which consisted of aging at 550 degrees C for 1 h, water quenching at room temperature and then newly heating at 550 degrees C. This procedure was repeated up to 300 times. The M23C6 and M6C carbide precipitation took place intragranularly and intergranularly for both aging treatments. The carbide coarsening was detected to occur with the increasing aging time. Nevertheless, the growth kinetics of precipitation occurred more rapidly in the case of cyclical aging. The specimen hardness decreased with the aging time in both cases; however, it occurred in shorter aging time for the cyclical aging. Nanoindentation testing indicated the increase in ductility with the aging time, and the cyclically aged specimens showed larger ductility than the isothermally aged specimens.

Automated summary

The study analyzed carbide precipitation during aging of 2.25Cr-1Mo steel at 550 degrees C. Carbide coarsening occurred with increasing aging time in both aging treatments, but the growth kinetics were faster in the case of cyclical aging. Specimen hardness decreased with aging time in both cases, with a quicker decrease in hardness for cyclical aging.