Precipitation behaviour during creep in 10%Cr steel for turbine rotors

Abstract

To reveal the precipitation behaviour in relation to creep deformation, microstructural investigation on the specimens creep-ruptured and creep-interrupted at various time under 600°C and 120 MPa was conducted in a 10%Cr steel forging. M₂₃C₆ carbides, Cr-rich M₂X and V-rich VX carbonitrides are detected on the heat-treated specimen. Most of the precipitates are M₂₃C₆ carbides and the recovery of the martensitic lath microstructure during creep are suppressed by them. There is a good relationship between the carbides growth and the creep deformation behaviour: the beginning of the significant coarsening corresponds to the transition from the primary to acceleration creep. The creep deformation is not affected by the precipitation of Laves phase and VX carbonitrides present around the grain boundaries.

This paper is part of a thematic issue on the 9th International Charles Parsons Turbine and Generator Conference. All papers have been revised and extended before publication in Materials Science and Technology.