Abstract

The aim of this study was to investigate the detailed macro/microstructures of three different surface coating technologies on the 6082-T6 aluminum alloy surface, namely Plasma Electrolytic Oxidation (PEO), Hard Anodizing (HA), and Plasma Spray Ceramic (PSC). Some of the PEO coatings were sealed with silicates. The microstructure investigations were performed using optical microscope, scanning electron microscope equipped with EDX analyzer and X-ray diffractometer. The microhardness of the base material and the coated layer were evaluated using Knoop indenter. All the coated layers appeared as two different layers. The PSC coating was the thicker followed by HA then PEO coating. The HA coating had irregular surface appearance, contained some cracks and appeared as an amorphous structure. The PSC coating was loose and had a poor bond with the substrate. The structure of PSC coating exhibited a lamellar geometry configuring 14% α-Al₂O₃ and 86% γ-Al₂O₃. The presence of porosity and voids was also observed. The PEO coatings were uniform and comprehensive. It adhered quite well to the substrate consisting of alumina (α and γ) phases. The ratio of γ alumina to α alumina was 79:31%. The sealed PEO coating with silicate had much lower porosity especially in the outer layer. All the coatings exhibited higher hardness than the substrate. The PEO coating showed the highest hardness compared with other coatings. The hardness of the PEO coating improved as the readings were taken away from the base. It displayed a maximum value in the middle and then started to reduce. The PSC coating has the highest roughness value followed by HA and then PEO coatings.

Graphic Abstract

中文翻译：

---

三种不同表面涂层技术在6082-T6铝合金上的组织表征

摘要

这项研究的目的是研究6082-T6铝合金表面上三种不同表面涂层技术的详细宏观/微观结构，即等离子体电解氧化（PEO），硬质阳极氧化（HA）和等离子体喷涂陶瓷（PSC）。一些PEO涂层用硅酸盐密封。使用光学显微镜，配备EDX分析仪的扫描电子显微镜和X射线衍射仪进行显微结构研究。使用努氏压头评估基材和涂层的显微硬度。所有涂层均表现为两个不同的层。PSC涂层较厚，其次是HA，然后是PEO涂层。HA涂层具有不规则的表面外观，包含一些裂纹并显示为无定形结构。PSC涂层疏松，与基材的粘合性差。PSC涂层的结构呈现出层状几何形状，构成14％α-Al₂ ö ₃和86％的γ-Al ₂ ö ₃。还观察到孔隙和空隙的存在。PEO涂层均匀且全面。它很好地粘附在由氧化铝（α和γ）相组成的基材上。γ氧化铝与α氧化铝的比例为79：31％。用硅酸盐密封的PEO涂层具有低得多的孔隙率，尤其是在外层中。所有涂层的硬度均高于基材。与其他涂层相比，PEO涂层显示出最高的硬度。PEO涂层的硬度随读数从底面移开而提高。它在中间显示一个最大值，然后开始减小。PSC涂层具有最高的粗糙度值，其次是HA和PEO涂层。

图形摘要