10302 Corrosion Fatigue Investigations of Austenitic Stainless Steels with Different Alloying Concepts and Grades of Cold Working

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Product Number: 51300-10302-SG

ISBN: 10302 2010 CP

Author: Clemens Vichytil, Robert Sonnleitner, Gregor Mori, Michael Panzenboeck and Rainer Fluch

Publication Date: 2010

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For applications under dynamic loads in aqueous, hot chloride containing media, austenitic stainless steels are often used. To reach a full and stable austenitic lattice, two different alloying concepts are commonly used. On the one hand, alloying with chromiumnickel and on the second hand, alloying with chromium-manganese-nitrogen results in a full austenitic lattice.

Two steels, one of each group in the solution annealed condition are investigated in this paper. Stress versus number of cycles curves and crack propagation rate curves were recorded in inert glycerin as reference medium and in 43 Wt% calcium chloride solution as corrosive medium, both at a temperature of 120°C. Crack initiations, fracture surfaces and fracture mechanisms of the two different steels were investigated and compared.

In addition, constant load tests, exposure tests, and electrochemical tests were done to determine damage mechanisms. In CaCl₂ less corrosion resistant CrMnN steel fails by stress corrosion cracking whereas CrNiMoN stainless steels shows very little corrosive attack and failure is caused mainly by corrosion fatigue. Due to oxide and roughness induced crack closure effects the effective rate of crack propagation at nominally the same ?K values is lower in the aggressive medium when compared to inert glycerine.

Keywords: Corrosion fatigue, stainless steels, austenite, fracture mechanism