Si含量对Ta12W合金表面Hf-Ta-Si涂层原位反应生成机理的影响

Effect of Si Content on In-situ Formation Mechanism of Hf-Ta-Si Coating on Ta12W Alloy Surface

摘要:

采用浆料反应烧结方法在Ta12W合金表面制备了Hf-Ta-Si复合涂层，探究了Si含量对Hf-Ta-Si涂层原位形成机理的影响。结果表明，30Hf:70Si涂层表面均一性差，含有一定孔洞，试样上部的涂层呈现4层梯度结构：最表层以HfSi和HfC为主，中间层形成 (Ta, Hf)₅Si₃固溶体，下层主体层为TaSi₂高硅相，涂层/基体界面层为Ta₅Si₃。但大量熔融Si在重力作用下导致下部涂层表面的Si富集。优化Hf:Si比例至40:60后，涂层表面的元素分布梯度差异降低，其表层仍以HfSi/HfC为主，但HfC析出更均匀；中间层(Ta, Hf)₅Si₃固溶体连续性增强；底层与涂层/基体界面过渡层未发生明显改变，整体形成更加致密的多层梯度结构，且涂层表面的均一性得到明显改善。此外，有机溶剂中的酸醇树脂通过高温热解与Hf原位反应生成的超高温陶瓷HfC，有望提高涂层的抗氧化性能和高温稳定性。

Abstract:

Using the slurry reaction sintering process to prepare Hf-Ta-Si composite coating on Ta12W alloy surface, the effect of Si content on the in-situ formation mechanism of the Hf-Ta-Si coating was investigated. Results show that 30Hf:70Si coatings exhibit inferior surface uniformity with some pores. The upper part of the sample displays a four-layer gradient structure: the outermost layer is primarily composed of HfSi and HfC, the middle layer consists of (Ta, Hf)₅Si₃ solid solution, the lower main-layer consists of TaSi₂, and the coating/substrate interface layer is Ta₅Si₃. However, the flow of molten Si under gravity leads to Si-enrichment on the lower part of the coating. After optimizing the Hf:Si ratio to 40:60, the gradient differences in elemental distribution on the coating surface decrease. The surface layer is dominated by HfSi/HfC, but the precipitation of HfC becomes more uniform. The continuity of the (Ta, Hf)₅Si₃ solid solution in middle layer is enhanced, whereas the lower layer and the interface transition layer remain unchanged. Overall, a denser multi-layer gradient structure is formed with improved surface uniformity. Additionally, the acid-alcohol resin in the organic solvent suffers high-temperature pyrolysis and in-situ reacts with Hf to generate the ultra-high-temperature ceramic HfC. This phenomenon is expected to enhance the oxidation resistance and high-temperature stability of coating.