Microscopic Investigation of Pitting Corrosion in Plasma Nitrided Austenitic Stainless Steel
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L. Escalada
Abstract
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 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.
Kurzfassung
Austenitischer Stahl UNS 31603 wurde unter Anwendung verschiedener Techniken nitriert und seine Beständigkeit gegenüber Lochkorrosion in einer Chloridlösung untersucht. Alle Nitriertechniken – LEII, PI·und herkömmliches Nitrieren im DC-Plasma – führten zur Ausbildung einer korrosionsbeständigen, „S-Phase“ genannten Nitrierschicht. Die Morphologie der Grübchen und die Schichtstruktur wurden mikroskopisch unter Einsatz optischer Mikroskopie, Elektronenmikroskopie, REM-FIB und mittels EDX untersucht und eine 3D-Rekonstruktion eines Grübchens mittels FIB-Tomographie ausgewertet. Wir kamen zu dem Ergebnis, dass die Grübchen ihren Ursprung in MnS-Einschlüssen nehmen. Ferner bildete sich ein durch die Nitrierschicht verlaufender Kanal und somit eine Verbindung Stahl/Elektrolyt. Unterhalb der Nitrierschicht konnte eine Auflösung der Ausgangslegierung beobachtet werden.
References / Literatur
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© 2014, Carl Hanser Verlag, München
Articles in the same Issue
- Contents/Inhalt
- Contents
- Editorial
- Editorial
- Technical Contributions/Fachbeiträge
- Assessing the Power of Electron Back Scattering Diffraction Characterization of Deformed F-138 Steel from the View Point of Crystal Diffraction
- Typical Zirconium Alloys Microstructures in Nuclear Components
- Review on Ceramic Interphases by Transmission and Scanning Electron Microscopy
- Microscopic Investigation of Pitting Corrosion in Plasma Nitrided Austenitic Stainless Steel
- Meeting Diary/Veranstaltungskalender
- Meeting Diary
Articles in the same Issue
- Contents/Inhalt
- Contents
- Editorial
- Editorial
- Technical Contributions/Fachbeiträge
- Assessing the Power of Electron Back Scattering Diffraction Characterization of Deformed F-138 Steel from the View Point of Crystal Diffraction
- Typical Zirconium Alloys Microstructures in Nuclear Components
- Review on Ceramic Interphases by Transmission and Scanning Electron Microscopy
- Microscopic Investigation of Pitting Corrosion in Plasma Nitrided Austenitic Stainless Steel
- Meeting Diary/Veranstaltungskalender
- Meeting Diary
