51314-4069-On the Slowdown of the Crack Propagation Rate of Austenitic Stainless Steel in Corrosive Environment

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Product Number: 51314-4069-SG

ISBN: 4069 2014 CP

Author: Marianne Kapp

Publication Date: 2014

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Austenitic stainless steels are frequently subjected to high chloride containing solutions and cyclic mechanical loading at the same time. Therefore it is of vital interest to gain knowledge about the crack growth behavior and the corrosion fatigue mechanism.In the current work a conventional austenitic stainless steel with 14 wt% Ni and 18 wt% Cr and a superaustenitic CrNiMoN stainless steel in different conditions are characterized in inert glycerin and 43 wt% CaCl2 at 120°C regarding their crack growth and corrosion fatigue behavior.Crack growth is thereby described by determining crack propagation rate curves and corrosion fatigue is studied by recording S/N curves at a stress ratio of 0.05. Using this stress ratio the destruction of the fracture surfaces is avoided as there are only tensile streses applied. The results of these experiments are correlated to observations on the fracture surface of selected tested specimens using scanning electron microscopy and electron dispersive X-ray spectroscopy. Additionally cyclic polarization curves are recorded and immersion tests are performed to evaluate electrochemical behavior.Results of S/N curves show only a moderate decrease of the fatigue limit for both steels in the corrosive media. Furthermore as expected the threshold Kth in the corrosive media is lower compared to the inert media. However surprisingly a pronounced slowdown of the crack propagation rate is observed in the Paris region in the corrosive media compared to glycerin.Possible explanations for this phenomenon like e.g. oxide induced crack closure effects will be critically discussed in this paper.