电机叶轮组合镀层斑点原因分析

Cause Analysis for Specks on Compound Coating of Motor Impeller Blades

通过体视显微镜、光学显微镜、扫描电镜及X射线能谱仪对ST13电机叶轮叶片表面进行分析检测,叶片表面为铜/镍/铬组合镀层。分析结果表明:叶片表面的斑点、锈蚀、起皮等缺陷是因氯离子渗入镀层导致的基体点蚀失效,叶片迎风面所受到的高压气流、镀层与钢铁基体的电位差等因素促进了腐蚀反应过程。叶片总的镀层厚度不足5μm,且作为中间层的镀铜层厚度不足0.3μm,没有起到应有的结合基体、阻隔腐蚀介质的作用。

Stereomicroscope,optical microscope,scanning electron microscopy and energy dispersive X-ray inspection were used to analyze and test the surface of ST13 motor impeller blades,on which a ＂copper ＋ nickel ＋ chromium＂ combination of compound coating is plated.The results show that the surface of the blades have specks,rusty corrosions,peeling and other defects caused by chloride ions penetrating into the matrix leading to pitting failure.The factors of high pressure air applied on the windward side of the blades,potential difference between coating and steel substrate,etc.accelerate the corrosion reaction process.The total coating thickness is less than 5 μm,and the middle layer of copper plating is less than 0.3 μm,so they do not play a role of binding matrix and obstructing corrosive media.