Effect of the Normalizing Temperature on the Short-Time Creep of Martensitic 10Cr–3Co–3W–0.2Re Steel with a Low Nitrogen Content

Abstract—The short-time creep of martensitic 10Cr–3Co–3W–0.2Re (wt %) steel with a low nitrogen content subjected to normalizing at temperatures of 1050 and 1100°C and subsequent tempering at 770°C for 3 h is studied under the following creep conditions: the temperature is 650°C, and the applied stress is 200, 180, and 160 MPa. The time to failure is found to increase substantially in the steel at an increased normalizing temperature as a result of a longer transient creep stage and a decrease in the minimum creep rate under short-time creep conditions. An increase in the normalizing temperature from 1050 to 1100°C doubles the mean size of the initial austenite grain from 55 to 105 μm; in this case, the mean martensite lath width (about 300 nm) and the free dislocation density (~2 × 1014 m–2) are independent of the normalizing temperature. The increase in the initial austenite grain size as a result of the increase in the normalizing temperature is found to be accompanied by an increase in the fraction and extent of low-angle boundaries, which favors a decrease in the mean size of grain-boundary M23C6 carbide particles during tempering and a Laves phase during creep. Moreover, an increase in the normalizing temperature causes a decrease in the rate of coarsening of grain-boundary M23C6 particles, tungsten-rich particles, and carbonitride Nb(C,N) particles uniformly distributed over the matrix volume by a factor of 5 (for the first two particles) and 31, respectively.