High temperature oxidation of Al4C3. (15th August 2020)

• Record Type: Journal Article
• Authors: Matthews, S.; Brown, Ian W.M.
• Is Part Of: Corrosion science. Volume 173(2020)
• Publication Date: 2020-08-15
• Subjects: Al4C3 -- High temperature corrosion -- Oxidation -- Selective oxidation -- XRD -- TGA; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2020.108793
• Languages: English
• ISSNs: 0010-938X

Abstract

Highlights: Concept exploits preferential oxidation of carbide in Al4 C3 -Ni alloy composite. Al4 C3 powder oxidation mechanism characterised at 950 °C and 1100 °C. Rapid initial mass gains, with longer term protective quadratic oxide growth kinetics. Multilayered oxide features correlated with equilibrium thermodynamic modelling. Abstract: Currently, high temperature corrosion resistant materials rely on the formation of an external surface oxide layer. This work is the first step in exploring an alternative coating concept in which one continuous phase in a two phase carbide–metallic binder coating system, preferentially oxidises internally within the composite. Controlled internal oxidation of the carbide would prevent oxide element consumption from the metallic binder, significantly improve adhesion of the oxide and reduce oxide growth stresses. Al4 C3 is considered as the carbide phase in order to form a protective Al2 O3 oxide. However, little has been presented on the high temperature oxidation mechanism of this compound. In this work the high temperature oxidation characteristics of Al4 C3 powders were characterised by TGA, XRD and cross-sectional SEM. At 950 °C and 1100 °C the carbide powder showed rapid initial mass gains, before transitioning to slower mass gains indicative of protective oxide formation. A complex four-layer oxide scale formed and was correlated with the phase distribution predicted by equilibrium thermodynamic modelling to postulate the oxidation mechanism.