Li Bo, Fan Lei, Bai Jie, He Jinhang, Su Jianfeng, Wang Song, Deng Chao, Liu Shifeng, Zhang Zhiqing
Electric Power Research Institute, Guizhou Power Grid Co., Ltd., Guiyang 550000, China.
An Shun Power Supply Bureau, Guizhou Power Grid Co., Ltd., Anshun 561000, China.
Materials (Basel). 2023 Oct 9;16(19):6612. doi: 10.3390/ma16196612.
Porosity is closely related to the corrosion and wear properties of a coating processed by thermal-spraying technology, and the quantitative characterization of porosity is a crucial part of the research on coating structures. The current image analysis method often uses the mechanical polishing method recommended by ISO to measure a coating porosity. This method has been proved to be an effective method for the characterization of oxide coatings. However, due to the significant differences in the physical and chemical properties between aluminum and oxides, this method may not be suitable for aluminum coatings, and a more appropriate approach needs to be explored. In this paper, the effects of three polishing technologies (mechanical polishing, argon-ion-beam polishing, and electrolytic polishing) on the porosity measurement of pure aluminum coatings were compared and studied. The research results showed that the commonly used mechanical polishing method and more advanced argon-ion-beam polishing method could not completely reveal the pore structure because SiC particles would be embedded in the pure aluminum coatings during mechanical polishing, filling large pores. Although electrolytic polishing technology had advantages in revealing the macroporous structure, it would introduce a microporous structure and oxides, which would affect the measurement of the coating porosity. The composite polishing technology (electrolytic polishing + argon-ion-beam polishing) could perfectly reveal the pore structure in the pure-aluminum coating, and the porosity of arc-sprayed aluminum coating was 9.9%, which was close to the macroscopic true value measured using the weighing method of 10.2%.
孔隙率与热喷涂技术制备的涂层的腐蚀和磨损性能密切相关，孔隙率的定量表征是涂层结构研究的关键部分。目前的图像分析方法通常采用ISO推荐的机械抛光法来测量涂层孔隙率。该方法已被证明是表征氧化物涂层的有效方法。然而，由于铝与氧化物在物理和化学性质上存在显著差异，该方法可能不适用于铝涂层，需要探索更合适的方法。本文比较研究了三种抛光技术（机械抛光、氩离子束抛光和电解抛光）对纯铝涂层孔隙率测量的影响。研究结果表明，常用的机械抛光法和更先进的氩离子束抛光法都不能完全揭示孔隙结构，因为机械抛光过程中SiC颗粒会嵌入纯铝涂层中，填充大孔隙。虽然电解抛光技术在揭示大孔结构方面具有优势，但会引入微孔结构和氧化物产物，影响涂层孔隙率的测量。复合抛光技术（电解抛光+氩离子束抛光）能够完美地揭示纯铝涂层中的孔隙结构，电弧喷涂铝涂层的孔隙率为9.9%，接近采用称重法测得的宏观真实值10.2%。
