Study of nobility of chromium nitrides in isothermally aged duplex stainless steels by using SKPFM and SEM/EDS

The relative nobility of Cr2N in duplex stainless steels (DSSs) was investigated in isothermally aged 2205 and 2507 DSSs using scanning Kelvin probe force microscopy (SKPFM) and SEM/EDS. The specimens contained nitrides, austenite and sigma phase but no ferrite. In these materials, Cr2N exhibits a higher Volta potential than sigma phase and austenite, implying the highest practical nobility of Cr2N compare to the surrounding phases. The composition and alloying effect can explain the relative nobility of the phases. The apparent “size effect” of small Cr2N on the measured Volta potential difference is probably due to the influence of surrounding matrix.