Effect of microstructure on hydrogen diffusion and trapping in a modified 9%Cr–1%Mo steel

The influence of the microstructure on hydrogen diffusion and trapping has been studied for a modified 9%Cr–1%Mo ferritic–martensitic steel (P91) in five different metallurgical conditions ranging from as quenched martensite to annealed ferrite. The material in these different conditions has been characterized and subjected to hydrogen permeation tests.The results show a strong dependence of hydrogen trapping on the metallurgical condition and this behavior may be related to the different density and nature of carbide particles. The role of dislocations on hydrogen trapping seems to be of secondary importance in this kind of materials.