Super-duplex stainless steels are recently developed high alloyed stainless steels that combine good mechanical properties with excellent corrosion resistance. Because of a high content of chromium and molybdenum, these alloys are susceptible to o-phase precipitation during short exposure to temperatures between 650 and 950°C. The effect of 800°C aging on o-phase formation and on the mechanical properties of a super-duplex stainless steel have been reported previously by the authorsJ This investigation concerns the effect of o-phase precipitation at 800°C on the corrosion behaviour in seawater and comprises anodic polarization scans and potentiostatic crevice corrosion tests. A serious deterioration of the corrosion resistance is found after aging times longer than 7 min, resulting in a drop of both the critical crevice corrosion temperature (CCT) and the breakdown potential (Ebd). The initiation of localized corrosion takes place next to the o-phase, in the newly formed secondary austenite (Y2).

No abstract

No abstract

The Effect of σ-Phase Precipitation at 800 • C on the Corrosion Resistance in Sea-Water of a High Alloyed Duplex Stainless Steel.-Aging of high alloyed duplex stainless steel at 800 • C for more than 7 min initiates localized corrosion in sea-water around the . sigma.-phase due to depletion of Co and Mo which results in a lower breakdown potential and critical crevice corrosion temp. and a higher critical current density. The σ-phase itself remains unaffected while the secondary austenite, γ2, formed during σ-phase transformation, is primarily attacked. Prior to the reduction of corrosion resistance, the mechanical properties deteriorate most rapidly after aging at 800 • C. -(WILMS, M. E.; GADGIL, V. J.; KROUGMAN, J. M.; IJSSELING, F. P.; Corros.

Unter den im Titel angegebenen Bedingungen tritt an dem untersuchten Stahl Rißbildung in 2 verschiedenen Potentialbereichen auf.