Creep deformation, rupture and ductility of Esshete 1250

Esshete 1250 is an austenitic steel with high creep strength and is used as a superheater boiler tube material in UK power stations. While the rupture strength of Esshete 1250 has previously been characterised, there has been little work on its creep deformation or creep ductility. Hence, the European Creep Collaborative Committee (ECCC) Working Group 3B Austenitic Steels has collated data and performed assessments of the creep deformation and creep ductility of Esshete 1250. In addition, a review of the previous creep rupture assessments identified that there were problems with the fits at temperatures of 550 and 600 °C. Thus, a new rupture assessment has been made, which alleviates these problems. The assessments of the creep ductility and creep rupture are based on the mechanisms of failure and it is shown that there are interactions between the two models. The creep deformation model is shown to give a good prediction of stress relaxation.