The oxidation and degradation of amorphous SiAlN coatings consisting of Si3N4 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.
|Early online date||10 Feb 2021|
|Publication status||Published - 10 Feb 2021|