Study of the microstructure of the grade 91 steel after more than 100 000h of creep exposure at 600°C

Clara Panait (1, 2) , W. Bendick (3) , A. Fuchsmann (2) , Anne-Françoise Gourgues-Lorenzon (1, 2) , Jacques Besson (1)

1 CDM - Centre des Matériaux
2 V & M France CEV
3 Salzgitter Mannesmann Forschung GmbH

This paper presents results on the evolution of microstructure (both matrix and precipitates) of an ASME Grade 91 steel that has been creep tested for 113,431h at 600°C under a load of 80MPa. The microstructure was investigated using transmission electron microscopy (TEM) and revealed chromium rich M23C6 carbides, MX-type precipitates, Laves phases and modified Z-phases. Only a small amount of modified Z-phase was found. In order to quantify coarsening of precipitates and growth of new phases during creep, the size distributions of the identified precipitates were determined by analysis of TEM images. In addition to this, the size distribution of Laves phases was determined by image analysis of scanning electron micrographs. Substructure modifications and creep damage were investigated on cross section of the creep specimen using Electron Backscatter Diffraction and Scanning Electron Microscopy.

Mots clés: P91 steel; Creep; Microstructure; Laves phases; Modified Z-phase; SEM; TEM

Domaines: Science des matériaux [cond-mat.mtrl-sci]

Clara Panait, W. Bendick, A. Fuchsmann, Anne-Françoise Gourgues-Lorenzon, Jacques Besson. Study of the microstructure of the grade 91 steel after more than 100 000h of creep exposure at 600°C. 2nd ECCC International Conference on Creep and Fracture in High Temperature Components: Design and Life Assessment Issues, Apr 2009, Zurich, Switzerland. pp.877-888. ⟨hal-00413783⟩