Creep fatigue crack behavior of two power plant steels

Abstract Crack initiation and crack growth under creep fatigue conditions were experimentally determined on a bainitic turbine rotor steel (30CrMoNiV4-11) and a martensitic pipe steel (X10CrMoVNb9-1). Side grooved compact tension (CT) specimens with 25 and 50 mm thickness as well as double edge notch tensile (DENT) specimens with 15 and 60 mm thickness have been tested in order to observe possible influences of geometry and thus to check the transferability of the specimen test results to the behavior of components. The creep fatigue crack test results can be described with the usual fracture mechanics parameters. A modified two-criteria-method can be used to estimate the crack initiation under creep fatigue conditions. The creep fatigue crack growth can be calculated from the accumulation of fatigue crack growth which is described by the Forman-law and creep crack growth which is described by the C ∗ -parameter.