The resistance to stress corrosion of austenitic stainless steel alloyed with nitrogen (ASS N25) was determined in comparison with AISI 316L steel. The research into stress corrosion cracking was performed by using corrosion elongation curves in a 50% CaCl2 solution, at 100°C, under axial tensile loadings defined as various percentages of Rp0,2, and with anodic polarization at a current density of 1.0 mA/cm2. The increased resistance of the nitrogen‐alloyed steel to stress corrosion is based on the occurrence of NH4+ ions, and the repulsive action of the negatively charged nitrogen atoms towards the Cl− ions on the interface between the passive layer and the corrosion medium. Additionally, the interstitially dissolved nitrogen is able to accelerate the local deformation hardening of the material at the crack tip, for which reason the critical stress needed for stress corrosion to occur, or for further growth of the crack if it has already occurred, is increased.

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Prediction of the remaining lifetime of stainless steels under conditions of stress corrosion cracking Vorhersage der Restlebensdauer von nichtrostenden Stä hlen unter Spannungsrisskorrosionsbedingungen M. Tandler * , L. Vehovar, V. Doleč ek and U. RotnikThe prediction of the lifetime of metal structures and equipment under conditions of stress corrosion is very complicated because of the complexity of this process of degradation. Recently a new method, based on the so-called corrosion elongation curves, has been found, which can be used to predict the time to failure under these conditions. By upgrading of these curves (and thus obtaining Upgraded Corrosion Elongation Curves -UCEC's) it has been possible to obtain a precise definition of the time needed for the initiation of the corrosion crack, and for its stable growth. It is upon this basis that diagrams for the prediction of remaining lifetime (DPRL's) have been developed. DPRL's can also be used to predict the values of various critical parameters which have to be achieved if a stress corrosion crack is to occur.Die Vorhersage der Lebensdauer von metallischen Bauwerken und Anlagen unter Bedingungen von Spannungsrisskorrosion ist wegen der Komplexität dieses Schädigungsprozesses sehr schwierig. Vor kurzem wurde eine neue, auf den sogenannten Korrosions-Dehnungs-Kurven basierende Methode gefunden, mit deren Hilfe die Lebensdauer unter diesen Bedingungen vorhergesagt werden kann. Durch Verbesserung dieser Kurven ist es möglich eine genaue Definition der notwendigen Zeit für die Initiierung des Korrosionsrisses sowie für stabiles Wachstum zu bekommen. Auf dieser Grundlage wurden Diagramme für die Vorhersage der Restlebensdauer entwickelt. Diese Diagramme können auch für die Vorhersage der Werte kritischer Parameter, die für das Auftreten von Spannungsrisskorrosion erreicht werden müssen, eingesetzt werden.

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