Creep characteristics and deformation analysis of service-exposed material using small punch creep test

Abstract

In this study, the creep characteristics and deformation analysis of service-exposed Cr5Mo are performed. Similar creep curves and deformation trends are found in both the uniaxial creep test and small punch creep test; however, the transient and tertiary creep stages are more apparent in the small punch test. The contribution of secondary creep time to the overall creep life is proven to be greater in the small punch creep test, corresponding to the tertiary stage which occupied most of the creep strain in the uniaxial creep test. When the creep deflection continues to increase, the percentages of low-angle grain boundaries and local misorientation increase, and the largest value appears in the necking region. On the basis of the microstructure analysis, a creep cavity model for the small punch creep is proposed for service-exposed Cr5Mo. The results demonstrate that the growth of creep damage has a stage from the constant speed to the accelerated speed creep. Ductile fracture behaviour is characterized. Finally, the Larson-Miller method is introduced and applied to predict the creep life of service-exposed material from shorter rupture time data.