Evaluation of corrosion behaviour in a 317L stainless steel strip welding using scanning Kelvin probe force microscopy

摘要

Scanning Kelvin probe force microscopy and magnetic force microscopy have been used in combination with SEM/EDS and immersion tests to study a 317L electroslag strip weld which contains austenite and interdendritic ferrite and sigma phase. The individual phases can easily be recognized from the compositional contrast, magnetic pattern and Volta potential variation. Austenite, which is paramagnetic, exhibits the highest Volta potential followed by non-magnetic sigma phase and ferromagnetic ferrite, respectively. Corrosion testing in acidic chloride solutions indicates that the Volta potential measured in air can be related to the tendency to uniform corrosion, while pitting corrosion shows different dependence. In both cases ferrite and sigma phase behaved in a similar manner, indicating that there was no specific detrimental effect of sigma phase on corrosion properties in this material.