Effect of Tungsten on a Dispersion of M(C,N) Carbonitrides in 9 % Cr Steels Under Creep Conditions

Two 9Cr–3Co–0.5Mo–VNb steels with 2 and 3 wt% W subjected to normalizing at 1050 °C and subsequent tempering at 750 °C for 3 h were crept at 650 °C under applied stresses ranging from 100 to 220 MPa. Both steels exhibit the creep strength breakdown at a rupture time of ~2000 h. The two-phase separation of M(C,N) carbonitrides to Nb- and V-rich particles occurs during tempering. No additional strain-induced coarsening of M(C,N) carbonitrides...