Inconel 718高温合金表面铝化物涂层的制备及其形成机制

Aluminide Coating Prepared on the Surface of Inconel 718 Superalloy and Its Formation Mechanism

摘要:

Inconel 718高温合金表面制备的铝化物涂层的组织结构及其形成机理，是提高该高温合金抗高温氧化和耐腐蚀性能的关键。采用化学气相沉积法在高温合金Inconel 718表面制备了铝化物涂层，通过结合使用材料热力学模拟软件JMatPro、X射线衍射仪、X射线能谱仪和扫描电子显微镜等表征手段，详细研究了铝化物涂层的微观组织结构。研究结果表明：在1 050 ℃温度条件下，经过1.5 h反应，Inconel 718表面生成了双层结构的铝化物涂层，其外层厚度为14.1 μm，主要由β-NiAl相组成，内层厚度为5.9 μm，由σ相和Laves相组成；外层的β-NiAl相形成是由Inconel 718高温合金中的Ni元素外扩散至表面后，与环境中的卤化铝反应而生成的；大量的Ni元素外扩散导致高温合金中的γ-Ni相减少，当高温合金中Ni元素的含量（原子分数）减少至49%时γ-Ni相中开始析出Laves相，当Ni元素的含量减少至40%时σ相也开始析出，当Ni元素的含量最终降至9%时Inconel 718高温合金完全转变成由σ相和Laves相组成的铝化物内层。研究结果深入揭示了涂层形成的机理，为优化铝化物涂层制备工艺提供了重要的理论基础。同时，对于Inconel 718高温合金的高温稳定性和腐蚀性能的提升具有实际应用价值。

Abstract:

Determining the microstructure and elucidating the formation mechanism of aluminide coatings on Inconel 718 superalloy surfaces are crucial steps in enhancing the alloy’s resistance to high-temperature oxidation and corrosion of. In this study， aluminide coatings were deposited on Inconel 718 superalloy surfaces by chemical vapor deposition. The microstructure of the aluminide coatings was thoroughly characterized by material thermodynamics simulation software JMatPro， along with X-ray diffractometry， X-ray energy spectrometry and scanning electron microscopy. The results showed that， following a 1.5 h reaction time at 1 050 ℃， the aluminide coating exhibited a distinctive double-layered structure on the Inconel 718 surface. The outer layer consisted predominantly of the β-NiAl phase with an average thickness of 14.1 μm， while the inner layer， with an average thickness of 5.9 μm， comprised the σ phase and Laves phase. The outward diffusion of a substantial amount of Ni from the Inconel 718 superalloy to its surface led to the formation of the β-NiAl phase through a reactive process with aluminum halides in the surrounding environment. This outward diffusion resulted in a reduction of the γ-Ni phase within the superalloy . As the Ni content in the superalloy decreased to 49 at.%， the Laves phase began to precipitate in the γ-Ni phase. A further reduction to 40 at.% of Ni content initiated the precipitation of the σ phase. Ultimately， with Ni content reaching 9 at.%， the Inconel 718 superalloy underwent a complete transformation into an aluminide inner layer， comprising the σ phase and the Laves phase. These findings provide comprehensive insights into the underlying mechanisms of coating formation， offering a theoretical foundation for optimizing aluminide coating processes. Moreover， the study holds practical significance in enhancing the high-temperature stability and corrosion resistance of Inconel 718 superalloys.