On the Precipitation Sequence in a 10%Cr Steel under Tempering

Precipitation sequence under tempering in a 10%Cr steel has been considered in details. Two different precipitation processes have been identified, concurrently. First, at 350°C, a dispersion of M2C phase with orthorhombic lattice appears. At 525°C, the M2C phase is displaced by the formation of M23C6 carbide. However, this process remains uncompleted. Dissolution of M2C phase occurs completely due to the formation and growth of more stable M6C phase as a result of tempering in the range of 650 to 770°C. Second, Nb-rich and V-rich M(C,N) carbonitrides precipitate in the temperature interval of 500–770°C. These dispersoids play a role of heterogeneous nucleation sites for precipitations of M23C6 and M6C carbides.