AZ31B镁合金表面喷熔Al涂层的组织和性能

Microstructure and Properties of Al Coating Sprayed on the Surface of AZ31B Magnesium Alloy

目的提高AZ31B镁合金的耐蚀性。方法采用氧乙炔在AZ31B镁合金表面喷熔Al涂层,对喷熔的Al涂层进行扫描电镜(SEM)分析,采用能谱仪(EDS)对涂层进行面扫描检测涂层元素的分布情况。利用电化学分析法、浸泡试验检测喷熔涂层的耐蚀性,用维氏硬度计测试喷熔涂层的硬度。结果喷熔的Al涂层与AZ31B镁合金基体结合良好,呈现冶金结合。喷涂过程中,喷熔的Al涂层呈等轴晶生长。通过面扫描结果可知,喷熔涂层中发现Mg元素,说明基体中的Mg元素发生了扩散。通过电化学测试可知,喷熔Al涂层的自腐蚀电压为-1.45 V,比AZ31B镁合金的自腐蚀电压(-1.5 V)降低了0.05 V;喷熔Al涂层的自腐蚀电流密度为1.58×10^(-4) A/cm^2,约为AZ31B镁合金自腐蚀电流密度(8.66×10-4 A/cm2)的1/5。由浸泡实验可知,喷熔Al涂层的平均腐蚀速率约为AZ31B镁合金的1/5倍。喷熔Al涂层的显微硬度是AZ31B镁合金基体硬度的2.9倍。结论喷熔Al涂层的组织较好,性能比镁合金基体有所提高。

Objective To improve the corrosion resistance of AZ31B magnesium alloy. Methods Al coating was sprayed on AZ31B magnesium alloy by using oxygen acetylene. Then scanning electron microscope （SEM） analysis was conducted on Al coating sprayed. The distribution of coating elements was detected by using energy dispersive spectroscopy （EDS）. The corrosion resistance of sprayed coating was detected by electrochemical workstation and immersion test; and the hardness was tested by Vickers. Results The combination of the A1 coating and the substrate was very good, which presented metallurgical bonding. During the spraying process, sprayed A1 coating showed equal axial grain growth. Through the surface scanning element distribution, Mg element was found in the spray coating, which indicated that Mg element had diffused in the substrate. According to the electrochemical workstation, the self-corrosion voltage of A1 coating was -1.45 V, 0.05 V lower than AZ31B magnesium alloy （-1.5 V）; the self-corrosion current of Al coating was 1.58×10^-4 A/cm^2, about 1/5 of AZ31B magnesium alloy （8.66×10^-4 A/cm^2）. The immersion test showed the average corrosion rate of Al coating was about 1/5 of AZ31B magnesium al- loy. Conclusion The microstructure and properties oral coating have been improved.