Oxidation behavior of Zr-Y alloyed Mo-Si-B based alloys

Three Mo-Si-B based alloys (Mo-12Si-10B, Mo-12Si-10B-1Zr and Mo-12Si-10B-1Zr-0.3Y (at.%)) were fabricated to study the effects of Zr and especially further addition of Y on the oxidation behaviors of alloys at 1250 °C. Mo-12Si-10B alloy shows good oxidation resistance due to the formation of a protective SiO₂ layer. However, as the result of the phase transformation of ZrO₂, triggering the breaking up of the protective SiO₂ layer, the addition of 1 at.% Zr (Mo-12Si-10B-1Zr alloy) leads to the catastrophic oxidation behavior. Further addition of 0.3 at.% Y (Mo-12Si-10B-1Zr-0.3Y alloy) eliminates this detrimental effect of Zr alloying by promoting the formation of monomorphic ZrSiO₄ instead of polymorphic ZrO₂ during oxidation. Besides, at the later oxidation stage (≥20 h), a continuous and compact Y₂Si₂O₇ layer forms on the scale surface, further improving the oxidation resistance.