Corrosion Fatigue of Duplex Stainless Steel X2crnimon22-5-3 Exposed to the Geothermal Environment of the Northern German Basin Under Different Applied Potentials and Surface Finishes

Abstract

The corrosion fatigue (CF) of duplex stainless steel X2CrNiMoN22-5-3 was investigated by means of applying purely alternating axial cyclic load to failure. Hour-glass shaped specimens with different surface finishing were tested at different stress amplitudes in a corrosion chamber allowing for the circulation of Northern German Basin electrolyte heated to 369 K. The influence of a protective potential on the CF was investigated by implementing a potentiostat. The significant increase of CF life range from 4,7 x 105 (free corrosion potential) to 107 cycles (potential range from USHE = –450 to –900 mV) was observed. The influence of surface condition was significantly demonstrated with polished surface finish showing a higher CF life expectancy than precisely turned surface finish. Microstructural analysis of the CF damage revealed horizontal grain attack within corrosion pit cavities, multiple fatigue cracks and preferable deterioration of austenitic phase.

Keywords: Corrosion, Fatigue, Duplex Stainless Steel, German, Basin, GHGT-14