The effect of pre-oxidation and thermal cycling on the corrosion behaviour of FeCrAlbased alloys in a coal gasifier atmosphere

• Published in: Corrosion science 1989, Vol.29 (6), p.735-765
• Main Authors: Sidky, P.S, Hocking, M.G
• Format: Article
• Language: English
• Subjects: alloys; Applied sciences; atmosphere; coal conversion; Corrosion; Corrosion environments; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; iron alloys; Materials science; Metals, semimetals and alloys; Metals. Metallurgy; Physics; Specific materials; thermodynamics
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/0010-938X(89)90110-8

The corrosion behaviour of laboratory cast alloys with additives of Zr, Hf, Ta and Mn as well as two commercially available alloys (Super FeCr Alloy EPE87 and Incoloy MA956) was examined in a simulated coal gasifier atmosphere containing chloride at 450 and 850°C. The P O 2 and P S 2 values were 10 −18 and 4 × 10 −5 bar at 850°C. Pre-oxidation was found to reduce the corrosion rate of the alloys (M, EPE and MA956) at 450 as well as 850°C. The corrosion rate of these alloys at 450 and 850°C is comparable. This indicates that the initial layer formed on pre-oxidation is capable of acting as a corrosion barrier at 450°C where normally no continuous protective layer forms at such a low temperature. In alloy C, the layer formed by pre-oxidation is not completely protective, leading to a higher corrosion rate at 450 than 850°C. The role of Ta, Hf and Si in reducing the corrosion rate of FeCrAlY alloys can be due to blocking of the oxide grain boundaries in the alumina layer formed by pre-oxidation. They were found in the scale whereas Zr and Y could be found in the underlying grain boundaries of the alloy.