Oxidation and degradation of amorphous SiAlN coating via forming Si-Si bond

Gao, Z, Kulczyk-Malecka, J ORCID: https://orcid.org/0000-0002-4905-3635, Zhang, Z, Liu, H, Zhang, X, Chen, Y, Hill, P, Kelly, P ORCID: https://orcid.org/0000-0003-1008-4941 and Xiao, P (2021) Oxidation and degradation of amorphous SiAlN coating via forming Si-Si bond. Corrosion Science, 183. p. 109318. ISSN 0010-938X

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Abstract

The oxidation and degradation of amorphous SiAlN coatings consisting of Si N and AlN phases, with 750 nm or 300 nm Mo interlayers on Zr alloy in steam environment at 1000 °C were investigated. After 1 h exposure, no detectable oxide scale formed on SiAlN/Mo (750 nm) coatings whereas SiAlN/Mo (300 nm) formed oxide scale. The downward diffusion of Si followed by relatively faster downward diffusion of N generated excessive Si and lean N, forming Si-Si bond in outermost surface of SiAlN, thereby resulting in oxidation. The degradation mechanism of amorphous nitrides was determined by elemental composition instead of reported amorphous or crystalline status. 3 4