Internal stresses analysis on welded joint in Grade 91 steel under creep test: synchrotron DRX tests and modelling

TL;DR

This study investigates creep damage in Grade 91 steel welded joints at high temperature using synchrotron XRD and finite element modelling, revealing localized damage in the heat affected zone.

Contribution

It combines in situ synchrotron XRD analysis with finite element modelling to understand creep damage localization in welded joints of Grade 91 steel.

Findings

Creep damage localizes in the ICHAZ with cavity band formation.

Significant strain evolution observed at the HAZ during creep.

Finite element analysis aligns with experimental damage patterns.

Abstract

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$^{\circ}$C, 100MPa 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 \textit{in situ} synchrotron XRD along the welded joint under creep conditions for the different creep life time. The experimental results show a significant strain evolution and creep damage characteristic on the welded joint, with a local maximum at the Heat Affected Zone (HAZ). Following this, a finite element creep strain analysis was performed for comparison with the experimental results.