Through-process modelling of welding and service of 9Cr steel power plant components under load-following conditions

This paper is concerned with the development of a through-process model to predict the in-service performance of high-temperature, 9Cr steel, power plant components. A multi-pass welding simulation is conducted using the finite element software Abaqus. A user-material subroutine, including microstructure evolution and a physically-based constitutive model, is employed to predict the mechanical response of the material during welding and to predict welding residual stresses. Points are sampled from the FE geometry and their microstructure parameters and residual stress values are used in a uniaxial code to predict the relative in-service lives of the different weld regions under load-following power plant operating conditions. It is shown that post-weld heat treatment significantly improves predicted life and that there is a strong correlation between predicted microstructure before service and the predicted in-service life.