Plasma electrolytic oxidation coatings on additively manufactured aluminum–silicon alloys with superior tribological performance
Plasma electrolytic oxidation coatings on additively manufactured aluminum–silicon alloys with superior tribological performance
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DOI：
10.1016/j.surfcoat.2022.128246
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发表时间：
2022-02
影响因子：
5.4
通讯作者：
Lili Wang;Guowei Wang;Hui Dong;M. Ye;Xiaoyuan Li;Ling Liu;Jinlong Pan;Zuoyan Ye
中科院分区：
文献类型：
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作者：
Lili Wang;Guowei Wang;Hui Dong;M. Ye;Xiaoyuan Li;Ling Liu;Jinlong Pan;Zuoyan Ye
由于对复杂几何结构的轻量化需求日益增加，增材制造铝硅合金引起了人们的广泛关注。然而，对于一些需要高接触压力和耐磨性的应用来说，它们的硬度不足和摩擦学性能差仍然是一个关键问题。在碱性电解液中制备了AM铝单键硅合金的电流控制等离子体电解氧化（PEO）涂层。为了获得具有优异力学性能的PEO涂层，通过调整硅酸盐和六偏磷酸盐的浓度对电解质体系进行了调制和优化。通过动电位极化试验，评价了AM铝单键硅合金在不同电解质中的腐蚀行为。采用扫描电子显微镜、x射线衍射、能量色散x射线能谱仪、显微轮廓仪和显微硬度计测定了硅酸盐和六偏磷酸盐对制备的PEO涂层的结构、组成、厚度、粗糙度和硬度的影响。在无润滑的情况下，用球盘摩擦计测试了PEO涂层的摩擦学性能。恒流模式下，硅酸有利于PEO过程；然而，形成了大量的莫来石和非晶体材料。六偏磷酸盐对AM铝单键si合金初始钝化膜的形成有不利的影响，在得到的涂层上形成许多缺陷。但它可以降低涂层的粗糙度，加速基体的溶解，促进氧化铝的形成，抑制莫来石和SiO2的形成。在混合电解质（硅酸盐与六偏磷酸盐的浓度比为~ 0.7-1）中制备的PEO涂层缺陷最少，硬度最高（~1300 HV），具有优异的摩擦学性能；涂层的磨损率仅为AM AlSi10Mg基体的1/150。提出了硅酸盐与六偏磷酸盐的协同作用，以及改性的PEO涂层在AM铝单键si合金上的生长机理。
Due to the increasing demand for lightweight structures with complex geometries, additively manufactured (AM) aluminum–silicon (Alsingle bondSi) alloys have aroused considerable attention. However, their insufficient hardness and poor tribological performance remain a critical issue for several applications requiring high contact pressures and wear resistance. Herein, current-controlled plasma electrolytic oxidation (PEO) coatings were developed on AM Alsingle bondSi alloys in alkali electrolytes. To obtain PEO coatings with excellent mechanical properties, the electrolyte system was modulated and optimized by adjusting the concentration of the silicate and hexametaphosphate. The corrosion behavior of AM Alsingle bondSi alloys in various electrolytes were evaluated via potentiodynamic polarization tests. The influence of silicate and hexametaphosphate on the structure, composition, thickness, roughness, and hardness of the prepared PEO coatings were determined using scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy system, microprofilometer, and microhardness tester. The tribological behavior of the PEO coatings were tested using a ball-disc-tribometer without lubrication. Silicate benefits the PEO process under the constant current mode; however, a mass of mullite and noncrystalline materials form. Hexametaphosphate adversely affects the formation of the initial passive film on AM Alsingle bondSi alloys, and many defects form on the obtained coating. But it can decrease the roughness of the coating and accelerate the dissolution of the matrix, promoting the formation of alumina and inhibiting the formation of mullite and SiO2. The PEO coatings, prepared in the mixed electrolytes (with a concentration ratio of silicate and hexametaphosphate of ~0.7–1), have the fewest defects and highest hardness (~1300 HV), and possess superior tribological performance; the wear rates of the coatings were only ~1/150th that of the AM AlSi10Mg substrate. Both the synergy of silicate and hexametaphosphate and the modified growth mechanisms of PEO coatings on AM Alsingle bondSi alloys have been proposed.