Field exposure of FeCrAl model alloys in a waste‐fired boiler at 600°C: The influence of Cr and Si on the corrosion behaviour

• Published in: Materials and corrosion Vol. 70; no. 8; pp. 1476 - 1485
• Main Authors: Eklund, Johan, Paz, Maria Dolores, Jönsson, Bo, Liske, Jesper, Svensson, Jan‐Erik, Jonsson, Torbjörn
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01-08-2019
• Subjects: Chromium; Correlation analysis; Corrosion; Exposure; FeCrAl alloys; high temperature corrosion; Nickel base alloys; Scanning electron microscopy; Silicon; Superalloys; Thickness measurement; waste-fired boiler
• ISSN: 0947-5117; 1521-4176; 1521-4176
• DOI: 10.1002/maco.201810618

The aim of this study was to examine the performance of FeCrAl model alloys in a waste‐fired boiler and investigate the influence of chromium and silicon content on the corrosion behaviour. The investigation was executed by utilising an air‐cooled probe, giving a material temperature of 600°C throughout a 672 hr exposure. The material loss measurements were performed by utilizing an ultrasonic thickness gauge in combination with scanning electron microscopy analysis. It was found that increasing the chromium content significantly reduced the overall material loss of the FeCrAl model alloys but further accelerated the corrosion attack on the windward side. Simultaneously, the increased chromium content caused embrittlement of the material. Minor additions of silicon drastically reduced the material loss of the FeCrAl model alloys, whereas the sample ring with no silicon present was completely deteriorated. The trends observed in this field study correlated well with what has been observed in previous laboratory studies. A state‐of‐the‐art alloy in the present environment, Inconel 625, was simultaneously exposed and showed similar performance to the silicon‐containing FeCrAl model alloys with ≥10 wt% Cr.
FeCrAl model alloys with varying Cr and Si contents were exposed in a waste‐fired boiler and subsequently analysed using scanning electron microscopy to investigate the change in corrosion behaviour. The obtained results showed drastic improvements of the corrosion behaviour, such as reduced material loss upon addition of Cr and Si. The Si‐containing FeCrAl model alloys with ≥10 wt% Cr displayed similar performance as the state‐of‐the‐art alloy Inconel 625.