Possible effect of Co on coarsening of M23C6 carbide and Orowan stress in a 9% Cr steel

Abstract

It has long been known that a cobalt addition increases the resistance to tempering in steels. This may be due to the fact that Co raises the Curie-temperature which retards diffusion. In the present work the effect of Co on coarsening of M23C6 in the 9% Cr steel P92 is studied by computer simulations. The results show that a final average radius of the carbides after 30 000 h at 600°C decreases with 30% with a Co addition of 10 mass%. This raises the Orowan stress with 30%. Moreover, it is assumed that slower particle coarsening also leads to a retarded coarsening of the martensite lath structure.