基材微弧氧化预处理对Ta12W表面Si-Cr-Ti-Zr涂层组织结构及抗高温氧化性能的影响

Effect of Substrate Micro-arc Oxidation Pretreatment on Microstructure and High-Temperature Oxidation Resistance of Si-Cr-Ti-Zr Coating on Ta12W Alloy

摘要:

为了降低真空熔烧反应过程中硅化物料浆与Ta12W合金基体互扩散反应对硅化物涂层抗氧化性能的影响，采用微弧氧化预处理工艺在Ta12W合金表面构建Ta₂O₅陶瓷层，随后采用料浆喷涂-真空反应烧制方法在预处理后的基体表面制备Si-Cr-Ti-Zr涂层，对比研究有/无微弧氧化陶瓷层的制备态涂层的显微组织结构、物相组成以及1600 ℃的恒温抗氧化性能。结果表明，400 V电压下制备的Ta₂O₅氧化物陶瓷层相对于350 V更为连续且孔隙更小；微弧氧化后Ta12W合金表面Si-Cr-Ti-Zr涂层由以Ti₅Si₃、Ta₅Si₃和ZrSi为主相的上层，以TaSi₂为主相的中层，以及以Ta₅Si₃为主相的涂层/基体界面反应层组成；有/无Ta₂O₅陶瓷层的Si-Cr-Ti-Zr涂层在1600 ℃下恒温氧化5 h后未发生失效，但Ta₂O₅氧化物陶瓷层的添加可以延缓涂层的高温氧化速率。

Abstract:

To mitigate the impact of interdiffusion reactions between the silicide slurry and Ta12W alloy substrate during vacuum sintering process on the oxidation resistance of the silicide coating, a micro-arc oxidation pretreatment was employed to construct a Ta₂O₅ ceramic layer on the Ta12W alloy surface. Subsequently, a slurry spraying-vacuum sintering method was used to prepare a Si-Cr-Ti-Zr coating on the pretreated substrate. Comparative studies were conducted on the microstructure, phase composition, and isothermal oxidation resistance (at 1600 ℃) of the as-prepared coatings with and without the micro-arc oxidation ceramic layer. The results show that the Ta₂O₅ layer prepared at 400 V is more continuous and has smaller pores than that prepared at 350 V. After micro-arc oxidation pretreatment, the Si-Cr-Ti-Zr coating on Ta12W alloy consists of three distinct layers: an upper layer dominated by Ti₅Si₃, Ta₅Si₃, and ZrSi; a middle layer dominated by TaSi₂; a coating/substrate interfacial reaction layer dominated by Ta₅Si₃. Both the Si-Cr-Ti-Zr coatings with and without the Ta₂O₅ ceramic layer do not fail after isothermal oxidation at 1600 ℃ for 5 h. Notably, the addition of the Ta₂O₅ ceramic layer reduces the high-temperature oxidation rate of the coating.