ZrB₂含量对Nb-Mo-ZrB₂复合材料氧化行为的影响

利用热压烧结法，在2400℃烧结温度下，制备了NbMo固溶体（此后记作(Nb,Mo)ss）基陶瓷颗粒增强复合材料。其中，ZrB2陶瓷增强相的体积分数分别为15%，30%，45%和60%。本文研究了在800℃，1000℃和1200℃下，ZrB2含量对复合材料抗氧化性和氧化产物演变的作用。试验结果表明，氧化温度和ZrB2含量均对复合材料的氧化行为有影响。从氧化速率常数角度讲，ZrB2-(Nb,Mo)ss复合材料的抗氧化性随ZrB2含量的增加而提高，随氧化温度的提高而降低。800℃-1000℃的氧化产物中含有膜状Nb2Zr6O17相,能作为屏障阻止氧气向基体扩散，因此在800℃-1000℃时，复合材料氧化速率较低。然而，在1200℃氧化时未发现Nb2Zr6O17相，MoO3的剧烈挥发和ZrO2的体积效应破坏了Nb2Zr6O17保护层，导致了氧化层严重剥落，材料的抗氧化性极差。综上，本文结合观察到的氧化产物形貌，详细阐述了不同ZrB2含量的复合材料在不同温度下的抗氧化机制。

The Influence of ZrB₂ Content on the Oxidation Behavior of Nb-Mo-ZrB₂ Composites

The NbMo solid solution (denoted as (Nb,Mo)ss hereafter) matrix ceramic composites reinforced with 15vol.%, 30vol.%, 45vol.%, and 60vol.% ZrB2 particles were fabricated by hot-pressing sintering at 2400°C. The effect of the ZrB2 content on the isothermal oxidation resistance and the oxide scales microstructure evolution exposed at 800°C, 1000°C, and 1200°C was investigated. The experimental results showed that both temperature and ZrB2 content have an influence on the oxidation behavior. The oxidation resistance of ZrB2-(Nb,Mo)ss composites increased with increasing ZrB2 content and decreased with increasing oxidation temperature from the view point of parabolic rate constant. The oxide scales at 800°C-1000°C contained special film-like Nb2Zr6O17, acting as a barrier for oxygen diffusing inwards and resulting in low parabolic rate constant. However, no Nb2Zr6O17 layer was observed at 1200°C because the volatile MoO3 and the volume effect of ZrO2 destroyed the Nb2Zr6O17 protective layer which resulted in severe spallation and poor oxidation resistance. Possible oxidation mechanisms at different temperatures with varying ZrB2 content were discussed and related to the observed oxide morphologies.