INFLUENCE OF BULK AND SURFACE COLD WORK ON CRACK INITIATION AND CRACK GROWTH OF AUSTENITIC STAINLESS STEELS UNDER SIMULATED BWR ENVIRONMENT

摘要

The influence of surface cold work (CW) strongly affects the crack initiation behavior of austenitic stainless steels under simulated light water reactor (LWR) environment. Within a parametric study crack initiation and crack growth rate (CGR) experiments were performed under simulated boiling water reactor (BWR) environment to determine critical conditions for plant components which might undergo crack formation and subsequent crack growth. Within this project AISI 347 was tested in solution annealed and/or several CW conditions. Comprehensive characterization in initial CW condition in comparison to as-tested material condition after e.g. exposure tests for crack initiation studies and CGR-experiments, clearly indicate the influence of localized plastic deformation within the grains of the material on the processes of crack initiation and propagation. With increasing amount of CW the addiction to intergranular cracking seems to increase due to high cumulative strains on active slip paths. Increased strength and reduced plasticity of the material in CW material condition superimpose the localized strengthening effects.