Scanning Kelvin probe force microscopy study of chromium nitrides in 2507 super duplex stainless steel—Implications and limitations

The effect of chromium nitrides on localized corrosion resistance of 2507 super duplex stainless steel was investigated in this study. The Volta potential difference measured with scanning Kelvin probe force microscopy (SKPFM) indicates that chromium nitrides with the size range of 80–230 nm precipitated isothermally at the ferrite/austenite phase boundaries may detrimentally affect the corrosion resistance due to the observed local Volta potential drop at the phase boundaries. Small quenched-in nitrides with the size range of 50–100 nm formed in the centre of the ferrite phase, on the other hand, may have small or no adverse effect on the corrosion resistance since they showed no difference in Volta potential relative to the matrix.