Microscopic Investigation of Pitting Corrosion in Plasma Nitrided Austenitic Stainless Steel

LISANDRO ESCALADA; SONIA P. BRÜHL; SILVIA N. SIMISON

PRAKTISCHE METALLOGRAPHIE

CARL HANSER VERLAG

Lugar: Munich; Año: 2014 vol. 51 p. 689 - 698

0032-678X

UNS 31603 austenitic stainless steel was nitrided using different techniques, and pitting corrosion resistance was analysed in a chloride solution. All nitriding techniques, LEII, PI· and convectional DC nitriding produced a nitrided layer called S phase which is corrosion resistant. Pits morphology and layer structure was investigated using optical and electronic microscopy, SEM-FIB, EDS, and a 3D reconstruction of a pit was assessed using FIB tomography. It was concluded that pits are initiated in a MnS inclusions and a channel was generated passing through the nitrided layer, connecting the steel with the electrolyte. Base alloy dissolution was observed beneath the nitrided layer.