Microstructural evaluation and creep deformation and rupture behavior of 9Cr-1Mo steel base metal, weld metal and weld joint

The deformation and creep rupture behaviour of 9Cr-1Mo ferritic steel base metal, weld metal and cross weld joint at 823 K over a stress range of 130- 250 MPa have been evaluated. The weld metal exhibited significantly higher creep rupture life than the base metal and the weld joint showed inferior c reep rupture life. The weld joint crept at a faster rate while the weld met al deformed at a slower rate than the base metal. Transgranular fracture pr evailed over the stress range examined. Microstructure developed across the weld joint and the changes of the microstructures that occurred during cre ep test have been characterized. Failure in the weld joint specimens took p lace in the intercritical structure of heat affected zone. Intergranular cr eep damage comprising cavities and cracks were not seen in the tested sampl es. Ductility was marginally reduced with increasing rupture time for all t he material conditions. The rupture elongation exhibited by base metal was higher than that shown by weld metal and weld joint.