在铝酸钠电解液中利用等离子体电解氧化(PEO)技术对铸态A356合金进行处理制备耐磨、耐蚀涂层.采用3种不同浓度的铝酸钠溶液(2、16和24 g/L NaAlO2)以及硅酸盐溶液(用以比较)制备涂层.利用球?块式干摩擦微动磨损试验(对磨材料为碳化钨)和电化学试验评价涂层的磨损和耐蚀性能.结果表明,在24 g/L NaAlO2溶液中处理480 s形成的氧化膜涂层具有最佳的保护性能.该涂层在30 N载荷下摩擦1800 s,其磨损率仅约为~4.5×10?7 mm3/(N·m).同时,该涂层具有很低的腐蚀电流密度(约为8.81×10?9 A/cm2).该实验发现,尽管膜层中α-Al2O3含量很低,涂层的致密程度和单层结构保证了其优异的性能.
Plasma electrolytic oxidation of a cast A356 aluminum alloy was carried out in aluminate electrolytes to develop wear and corrosion resistant coatings. Different concentrations of 2, 16 and 24 g/L NaAlO2 solutions and a silicate electrolyte (for comparison) were employed for the investigation. Wear performance and corrosion resistance of the coatings were evaluated by WC (tungsten carbide) ball-on-flat dry sliding tests and electrochemical methods, respectively. The results show that the coating formed for a short duration of 480 s in 24 g/L NaAlO2 solution generated the best protection. The coating sustained 30 N load for sliding time of 1800 s, showing very low wear rate of ~4.5×10?7 mm3/(N·m). A low corrosion current density of ~8.81×10?9 A/cm2 was also recorded. Despite lowα-Al2O3 content of the coating, the compact and nearly single layer nature of the coating guaranteed the excellent performances.
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