Intergranular Corrosion and Fatigue Strength of Nonsensitized Austenitic Stainless Steels

Abstract

Intergranular corrosion tests of nonsensitized austenitic stainless steels and rotating-bending fatigue tests of intergranularly pre-corroded stainless steels were carried out to investigate the effects of intergranular corrosion on fatigue strength.
The following results were obtained.
(1) Ditches 10 to 20 μm in depth due to intergranular corrosion are found on as-received stainless tubes.
(2) The depth of intergranular corrosion in strongly oxidizing media increases linearly with exposure time on a full logarithmic scale.
(3) Fatigue strength decreases with the increase of the depth of intergranular corrosion. Endurance limit of the stainless steels which intergranularly corroded up to the depth of 60 to 120 μm decreases to 68% of that of as-machined stainless steels. As fatigue cracks initiate at the bottom of the ditches, intergranularly corroded stainless steels should be treated as notched materials.