Assessment of creep rupture strength for the new martensitic 9% Cr steels E911 and T/P92

Abstract

The application of new heat resistant steels in power plants requires reliable long term creep rupture strength values as basis for design. A major task of ECCC (European Creep Collaborative Committee) is to supply such values by making assessments of large creep data sets. Different assessment methods have been used in the past involving different extrapolation techniques. The modern martensitic 9% Cr-steels E911 (T/P911) and T/P92 have complex microstructures changing with service exposure. Since the microstructural changes have an effect on strength, an extrapolation of long term strength properties becomes most difficult. Now that long term creep test results are available it has been shown that a revision of earlier assessments on E911 and T/P92 is necessary. New assessments are presented using different methods. The advantages of a heat by heat preassessment are discussed.

Keywords:

• creep rupture strength
• data assessment
• E911
• T/P911
• T/P92