Effect of Ni and Mn on the Creep Behaviour of 9–10 %Cr Steels with Low N and High B

Creep behavior and microstructure of two 9–10 %Cr–3 %Co martensitic steels with high B and low N was examined. A 10 %Cr steel with low Ni and Mn additives exhibits superior creep resistance and no creep strength breakdown appears at 650 °C. In this steel a dispersion of boundary M23C6 carbides and Laves phase remains nearly unchanged under creep condition and no significant coarsening of lath structure takes place. In contrast, a 9 %Cr steel...