Jivkov's articles
Grain boundary control for improved intergranular stress corrosion cracking resistance in austenitic stainless steels: new approach
Abstract
The present paper provides an overview of a new approach which has focused on the behaviour of special grain boundaries in sensitised austenitic stainless steel. The aim of the work was to develop
a general model for stress corrosion cracking, which would ultimately be capable of predicting the effects of the degree of sensitisation, the connectivity of special boundaries and the influence of stress
gradients, such as those developed from surface preparation (machining or peening) or due to the stress concentration effect of pit formation. Experimental work using electron backscatter diffraction
analysis and in situ high resolution computed X-ray tomography has correlated cracking with the microstructure in a type 304 austenitic stainless steel. In situ three-dimensional observations
demonstrated that annealing twins cause local crack arrest and diversion, leaving non-fractured ligaments in the wake of the cracking path. The mechanical effects of the deformation and failure of these
bridges have been modelled, demonstrating that special grain boundaries cause crack tip shielding. Increasing the fraction of special boundaries and decreasing grain size are both predicted to increase
stress corrosion cracking resistance. Experimental observations using room temperature intergranular stress corrosion tests and high temperature autoclave tests confirm these predictions for thermomechanically
processed microstructures. The effects of applied stress and stress gradients are also predicted by the model, which may be extended to include the kinetics of crack growth, clustering of grain boundary types
and variation of the degree of sensitisation.