Correlation between microstructure and long-term creep behaviour of 9% Cr steel P92 for advanced power plants.

The microstructure and creep properties of the 9% Cr-0,5Mo-1,8W-V-Nb steel P92, a Japanese steel developed for advanced coal-fired power stations with operating steam temperatures around 600 degrees centigrade have been investigated. The study showed that the microstructural changes responsible for the decreasing creep rupture strength at temperatures 600 and 650 degrees centigrade were a marked decrease in dislocation density, an increase in subgrain size with continuous polygonization of the dislocation structure, and slight coarsening of the M23C6 and MX precipitates.