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Influence of Sodium Hydroxide on the Austenitic 330Cb Alloy Oxidation at High Temperature

2017; Springer Science+Business Media; Volume: 87; Issue: 5-6 Linguagem: Inglês

10.1007/s11085-017-9722-8

1573-4889

H. Buscail, Raphaël Rolland, F. Riffard, C. Issartel, Cécile Combe, Pierre-François Cardey,

High Temperature Alloys and Creep

Sodium hydroxide is found on metallic conveyor belts as residue of the degreasing process of metallic screws put inside heat treatment furnaces at 900 °C. The 330Cb (Fe–34Ni–23Cr–1Nb–1.55Si) alloy is used to build these conveyor belts. With time, the amount of sodium hydroxide increases on the 330Cb steel surface. The aim of this work was to show the influence of the NaOH amount on the 330Cb oxidation during 48 h, at 900 °C. Results showed that, on this austenitic steel, protective silica-scale formation is promoted by low-oxygen-containing gaseous environments and the high alloy silicon content. With low NaOH deposits, the oxide layer is adherent and an SiO2 cristobalite subscale is formed. It was also demonstrated that sodium combines with niobium to form NaNbO3. When the NaOH amount exceeds 0.265 mg cm−2 on the alloy surface, severe oxidation is observed leading to a fast-growing FeCr2O4 oxide scale.