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钽表面(WMoCrTa)Si2高熵硅化物涂层制备及1400 ℃抗氧化性能

Preparation and oxidation resistance at 1400 ℃ of (WMoCrTa)Si2 high entropy silicide coatings on tantalum surface

  • 摘要: 以硅化物粉末为原料,采用料浆烧结+卤化物活化包埋渗硅两步法在钽金属表面制备了(WMoCrTa)Si2高熵硅化物涂层,研究了1400 ℃温度下涂层的抗氧化性能。结果表明,最终形成的涂层呈现四层结构,由外至内依次为多孔高熵硅化物相层、铬钽硅化物层、致密TaSi2层及Ta5Si3过渡层,总厚度约186 μm。在1400 ℃静态氧化环境中,该涂层可作为有效防护屏障为钽基体提供超过14 h的高温保护,其氧化增重曲线呈现“缓慢增长-快速增重-趋于稳定”三阶段特征。氧化初期,涂层表面快速形成致密SiO2保护膜,Cr元素优先与氧反应生成Cr2O3,进而与Ta2O5反应形成CrTaO4,二者协同作用显著提升氧化膜的结构稳定性与阻氧能力;氧化后期,受SiO2膜剥落、内部孔洞增多等缺陷影响,涂层保护效果逐渐变差。

     

    Abstract: The (WMoCrTa)Si2 coatings were prepared by two-step process, involving slurry sintering followed by halide-activated pack cementation, with the silicide powders as the raw materials. The oxidation resistance at 1400 ℃ of the coatings on tantalum surface was investigated. In the results, the four-layer structure is present in the final coatings: the porous high-entropy silicide layers, the chromium-tantalum silicide layers, the TaSi2 interlayers, and the innermost Ta5Si3 layers with the overall thickness of 186 μm. Under the static air oxidation at 1400 ℃, the coatings can protect the tantalum substrate for over 14 h, with the mass gain curves showing a three-stage behavior as slow growth, rapid gain, and gradual stabilization. In the initial stage, the dense SiO2 scale is formed rapidly, Cr is preferentially oxidized to Cr2O3, which further reacts with Ta2O5 to form CrTaO4, and the synergy enhances the stability and oxygen-blocking ability of the coatings. In the later stages of oxidation, the protective performance of the coatings finally deteriorates due to the SiO2 spallation and the internal pore proliferation.

     

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