The theta approach to creep and creep fracture of forged 1Cr–1Mo–0.25V steel

Abstract

Tensile creep and creep fracture properties are presented for a forged 1Cr–1Mo–0.25V rotor steel over stress ranges giving creep lives up to about 1000 hours at 783 to 863 K. The results are described by adopting traditional power-law approaches, before documenting the additional information gained by quantifying the creep curve shapes using the θ methodology. In this way, the observed behaviour patterns are explained in terms of the dislocation processes governing strain accumulation, the localized microstructural instability causing the tertiary acceleration and the eventual neck formation which leads to transgranular failure. Moreover, the θ relationships derived from this short-term test programme are shown to allow prediction of the comprehensive long-term data sets for forged 1Cr–1Mo–0.25V steels determined by the National Research Institute for Metals, Japan.