Precipitation Characterization and Creep Strength at 600°C for Creep Resistant Cr–Mo Steel

Abstract

The creep strength of 5Cr-0.5Mo steel was determined at 600°C and 78–170 MPa, as well as its relation to the microstructural changes during the creep tests. The microstructural characterization showed that the creep tests were conducted under the presence of a mixture of both intergranular and intragranular M₇C₃ and M₂₃C₆ carbides dispersed in the ferrite matrix. The n exponent of Norton-Bailey law suggested that the creep deformation process occurred through the ferrite grains, which conducted to a transgranular ductile- fracture mode after creep testing. The creep strength of this steel is directly related to the average radius and number density of carbides present during the test. The ferrite grain size of 5 µm seemed to cause an enhancement of the creep strength for this steel in comparison to that of other similar steels reported in the literature.