以变形镁合金AZ31B为试验基材, 在其表面采用高功率CO2气体激光熔覆了Al-Si基纳米Si3N4粉末。采用金相观察、X射线衍射分析、能谱分析、硬度测试和腐蚀性能测试等手段, 研究了激光熔覆层的微观组织结构及表面性能。研究结果表明, 激光熔覆层主要由上部的树枝晶、中部呈线性排列的黑色相和下部的粗大树枝晶组成。当纳米氮化硅含量为1%时, 熔覆层主要由Al、AlN、Al9Si和Mg2Si组成。熔覆层的硬度最高达到235 HV0.05, 是镁合金基体的4～5倍。熔覆层的耐腐蚀性能得到了改善, 其腐蚀电位为－1 204 mV, 比母材提高了382 mV; 腐蚀电流密度为0.070 5 mA·cm-2, 比母材降低了约一个数量级。

In this paper, laser surface cladding Al-Si +nano-Si3N4 composite coating on AZ31B magnesium alloy with a CO2 laser. The microstructure and properties of the cladded layer were investigated with optical microscopy, X-ray diffraction, energy dispersive spectrometer, and Vickers hardness and corrosion resistance test. The results showed that the cladding layer was mainly composed of the upper dendrites, the central black phase which presenting a linear arrangement and the bottom thick branches crystal microstructure. When nano-Si3N4 content was 1%, the phase of cladding layer was Al, AlN, Al9Si and Mg2Si. Microhardness of the caldded layer was about 235 HV0.05, which was 4～5 times of the matrix’s. The corrosion resistance of magnesium alloy improved significantly. The corrosion potential of the cladded layer was －1 204 mV, which raised 382 mV compared the AZ31B magnesium alloy substrate, and the corrosion current density was 0.070 5 mA·cm-2 which reduced one order of magnitude compared with the substrate.