Corrosion sous contraintes : susceptibilité d’un acier inoxydable austénitique

Influence de l’écrouissage et des contraintes résiduelles

Influence of plastic deformation and residual stresses on stress corrosion susceptibility of an a ustenitic stainless steel

Résumé

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Abstract

In this study, the susceptibility of a stable austenitic stainless steel Z2CND 17-12 (316 L) to stress corrosion under plastic deformation (or work-hardening) and stresses (both applied and residual) in a boiling solution of MgCl₂(44%) is examined. The mechanical state of stress and plastic deformation of the surface layers of the specimens is carefully defined by X-ray diffraction. Corrosion tests on specimens under applied uniaxial traction reveal a critical, very low threshold of cracking at about 80 MPa which is, nevertheless, sensitive to any initial residual stresses, but not workhardening, obtained by traction loading prior to the corrosion tests. On the other hand, for tests under residual stresses obtained by elasto-plastic bending of specimens initially strained by uniaxial traction, a markedly higher threshold is found - always greater than 150 MPa. In this case, the degree of work-hardening is a very important factor whose effect may be beneficial or detrimental depending on its level.