微弧氧化法制备2A12铝合金高发射率涂层的性能研究

Study on Properties of High Emissivity Coating of 2A12 Aluminum Alloy Prepared by Micro-Arc Oxidation

摘要:

铝合金作为航天电推进器用加速喷射电真空器件的常用材料得到广泛应用，然而其在应用过程中容易出现过热现象，进而影响工作性能和使用寿命。因此，严重限制了铝合金的进一步应用。为了有效地解决铝合金过热问题，需将其表面聚集的热量进行有效地散发。采用微弧氧化（MAO）技术，以磷酸盐为基础电解液的主要成分，以FeSO₄为添加剂，通过调控FeSO₄的浓度，在2A12铝合金表面制备出组分分布均匀的具有红外高发射率的热控辐射涂层。使用扫描电子显微镜、能谱仪、X射线衍射仪、涡流测厚仪、粗糙度仪、万能材料试验机、傅里叶变换红外光谱仪，对不同FeSO₄浓度下制备的微弧氧化涂层的表面形貌、元素组成、相组成、厚度、粗糙度、结合强度及红外发射率进行了系统分析。结果表明，随着FeSO₄浓度从0 g?L^-1增加到8 g?L^-1，涂层表面的孔洞数量逐渐减少，孔洞尺寸逐渐增加且出现裂纹，涂层的厚度和粗糙度逐渐增加。其中，厚度从17.2 μm增加至39.1 μm，粗糙度从1.94 μm增加至2.96 μm。另外，XRD及XPS分析结果表明，涂层主要由α-Al₂O₃、γ-Al₂O₃和Fe₂O₃相组成，且均为基体与电解液反应生成的产物。值得注意的是，当FeSO₄浓度为6 g?L^-1时，涂层的结合强度、红外发射率值达到最佳值，分别为39.8 MPa和0.909。本研究为2A12铝合金在航空航天领域中进一步应用提供了理论依据。

Abstract:

Aluminum alloys are widely used as materials for electric vacuum devices in aerospace electric propulsion systems. However， they tend to overheat during operation， significantly impacting performance and service life， thus limiting their border application. Effectively dissipating the heat accumulated on the surface is a key approach to addressing this issue. In this context， a high-emissivity thermal control and radiative heat dissipation coating was developed on aluminum alloy surfaces using micro-arc oxidation （MAO） technology. Phosphate was selected as the primary component of the electrolyte， with FeSO₄ added as an additive. By adjusting the concentration of the additive FeSO₄ in the electrolyte， a uniform， high-emissivity infrared coating was successfully fabricated on the surface of 2A12 aluminum alloy. Scanning electron microscope， energy spectrometer， X-ray diffractometer， eddy current thickness meter， roughness meter， universal material testing machine and Fourier transform infrared spectrometer were used to analyze the surface morphology， elemental composition， phase composition， thickness， roughness， bonding strength and infrared emissivity of the micro-arc oxidation coatings prepared at different concentrations of FeSO₄. The results show that as the FeSO₄ concentration increased from 0 g?L^-1 to 8 g?L^-1， the number of holes on the coating surface gradually decreased， while pore size increased， and cracks began to form. The coating’s thickness and roughness of the coating increased from 17.2 μm to 39.1 μm， and from 1.94 μm to 2.96 μm， respectively. XRD and XPS analyzes revealed that the coatings consisted primarily of α-Al₂O₃， γ-Al₂O₃ and Fe₂O₃ phases， which originated from the substrate and electrolyte. Notably， at a FeSO₄ concentration of 6 g?L^-1， the coating exhibited optimal bonding strength and infrared emissivity， measured at 39.8 MPa and 0.909， respectively.