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Abstract
High-temperature components with notches, defects and flaws may be subjected to crack initiation and crack propagation under service conditions. To study these problems and to support an advanced remnant life evaluation, fracture mechanics procedures are required. Due to a more flexible service mode of power plants an increase of start up and shut down processes can be observed. Therefore knowledge of life assessment and integrity of such components is decisive.
In order to enlighten these problems for steam power plant components, crack initiation time and crack growth rate of modern martensitic steels of type 10CrMoWVNbN were determined at 550 and 600°C in forged and cast conditions. For the experiments, side grooved compact tension, C(T), specimens were used as well as side grooved double edge notched tensile, DEN(T), specimens.
Creep/creep-fatigue crack initiation and crack propagation can be described with the usual fracture mechanics parameters C* and KI and a modified two-criteria method was established in order to describe creep fatigue crack initiation.