High-temperature cyclic oxidation behavior and mechanism of Mo₂FeB₂-based cermets with various boron contents

In this study, cyclic oxidation behavior and mechanism of Mo₂FeB₂-based cermets have been investigated by varying the boron content. The parabolic curves of mass gain confirmed the formation of the protective oxide layer. Mo₂FeB₂-based cermets with boron content of 6 wt.% had the lowest mass gain due to the denser and continuous oxide layer. A typical multi-layer structure could be observed in the cross-section, which was mainly composed of Fe oxide, borate and molybdate. The borate layer could effectively inhibit the diffusion of oxygen to protect the matrix from rapid oxidation. Furthermore, higher boron content could facilitate the oxide layer to be denser, which is beneficial to the oxidation resistance. However, the “pesting oxidation” would appear after 50 h oxidation at 800 °C, which causes the curves of mass gain to transform from parabolic to linear trend.