The analysis of internal stresses on a welded joint in Grade 91 steel under creep test loading: Synchrotron X-ray diffraction measurements and modelling

The analysis and understanding of creep damage of Grade 91 steel welded joints is an important topic in the energy industry. Creep tests on welded joints were carried out at 600 • C, 100 MPa and then interrupted at 0%, 10%, 30%, 50%, 80% of the expected life and after failure. Creep damage is characterised by cavity bands located exclusively in the core of the sample in the InterCritical Heat Affected Zone (ICHAZ). These samples were tested using in situ synchrotron X-ray Diffraction (XRD) along the welded joint under creep conditions for the different creep times. The experimental results show a significant evolution of strain and creep damage characteristics on the welded joint, with a local maximum at the Heat Affected Zone (HAZ). Subsequently, a finite element creep strain analysis was performed for comparison with the experimental results.