2003 Volume 43 Issue 1 Pages 112-118
Effects of W and Co on creep deformation and microstructure of fully annealed and precipitation strengthened 15Cr-3W ferritic steels at 923 and 973 K have been investigated, and the strengthening effects of W and Co in a long-term and high temperature service condition have been discussed. The effect of Co addition on the creep rupture strength of the steels is higher than that of the further addition of W in the shortterm. However, the creep rupture life of the steel with 6 mass% W is longer than that of the steel with 3 mass% Co at the low stress condition of 50 MPa and 973 K. The increase in W content promotes the formation of intermetallic compounds such as χ phase. The addition of Co promotes the precipitation of fine M23C6 carbide within grains. The precipitation of carbide by Co addition is effective in improving the shortterm creep strength for higher stress regions, whereas the formation of intermetallic compounds by W addition is more effective for lower stress and long-term creep life.
