CVD法制备Inconel 718 高温合金表面铝化物涂层高温氧化行为研究

High-Temperature Oxidation Behavior of Chemical Vapor Deposition Aluminide Coatings on Inconel 718 Superalloy

摘要:

Inconel 718高温合金是燃气轮机和航空发动机热端部件的关键核心材料，其表面通常制备有铝化物涂层，起到提高抗氧化和热腐蚀性能的作用。理解铝化物涂层的高温氧化行为，是提高部件抗高温氧化能力的关键。采用化学气相沉 积（CVD）技术，在Inconel 718高温合金表面制备了铝化物涂层，在大气环境、950 ℃条件下开展了恒温氧化测试，采用扫描电子显微镜、X射线衍射和X射线能谱等手段，研究了其高温氧化行为，并与Inconel 718高温合金进行对比。结果表明：In-conel 718高温合金表面制备的CVD铝化物涂层，其表面粗糙，具有双层结构。外层为富含Ni和Al元素的β-NiAl层，平均厚度为14.1 μm，内层为富含Fe和Cr元素的σ相与富含Nb、Mo和Fe元素的Laves相共存的互扩散层，平均厚度为5.9 μm 。恒温氧化后，Inconel 718高温合金表面氧化生成了Cr₂O₃膜，而CVD铝化物涂层表面氧化生成了α-Al₂O₃膜。Cr₂O₃膜和α-Al₂O₃膜的生长都遵循抛物线型生长规律，Cr₂O₃膜的生长速率常数为0.86 μm?h^-1/2，α-Al₂O₃膜的生长速率常数为0.15 μm?h^-1/2。此外，观察发现Inconel 718 高温合金发生了内氧化，而 CVD铝化物涂层未出现内氧化，两者氧化行为差异的原因在于CVD 铝化物涂层中的β-NiAl相，其氧化生成均匀、连续、致密的α-Al₂O₃ 膜，阻止了内部金属发生进一步氧化。本研究揭示了Inconel 718高温合金和CVD铝化物涂层的抗高温氧化作用机理，为Inconel 718高温合金用高抗氧化性CVD铝化物涂层的制备及应用提供了技术支撑。

Abstract:

Understanding the high-temperature oxidation behavior of aluminide coatings on Inconel 718 superalloy is crucial for enhancing the high-temperature oxidation resistance of hot-end components in gas turbines and aeroengines. In this study，the aluminide coating was deposited on the surface of Inconel 718 superalloy by chemical vapor deposition（CVD）， and isothermal oxidation tests were conducted on the Inconel 718 superalloy and the CVD aluminide coating at 950 ℃ under atmospheric environment. The high-temperature oxidation behavior of the CVD aluminide coating before and after oxidation， as well as the Inconel 718 superalloy was investigated by characterization methods such as scanning electron microscopy，X-ray diffraction， and energy-dispersive X-ray spectroscopy. The results show that the CVD aluminide coating deposited on the surface of Inconel 718 superalloy exhibits a rough surface and a bilayer structure. The outer layer is a Ni-and Al-rich β-NiAl layer with an average thickness of 14.1 μm. And the inner layer is an interdiffusion layer with an average thickness of 5.9 μm in which the σ phase rich in Fe and Cr elements and the Laves phase rich in Nb，Mo，and Fe elements coexist. After isothermal oxidation tests，the oxide scale formed on the surface of Inconel 718 superalloy is Cr₂O₃，while the oxide scale formed on the surface of CVD aluminide coating is α-Al₂O₃. The growth of Cr₂O₃ and α-Al₂O₃ follows the parabolic growth law. The growth rate constant of Cr₂O₃ of Inconel 718 superalloy is 0.86 μm?h^-1/2，while the growth rate constant of α-Al₂O₃ of CVD aluminide coating is 0.15 μm?h^-1/2. Inconel 718 superalloy experienced internal oxidation，while no internal oxidation was observed in the CVD aluminide coating. The presence of β-NiAl phase in the CVD aluminide coating is the fundamental cause of the difference in oxidation behavior between Inconel 718 superalloy and CVD aluminide coating. This study elucidates the mechanism of high-temperature oxidation resistance of Inconel 718 superalloy and CVD aluminide coatings，and provides technical support for the preparation and application of high oxidation resistance CVD aluminide coatings for Inconel 718 superalloy.