低能量密度气体激光熔凝AZ31B镁合金的微观组织与磨损性能

Microstructure and Wear Resistance of Low Energy Density Gas Laser Surface Melting on AZ31B Magnesium Alloy

为提高镁合金表面的耐磨性,利用5 kW横流连续CO2激光器在AZ31B镁合金表面采用低能量密度激光能量制备了无裂纹、气孔等缺陷的熔凝层。通过光学显微镜、X射线衍射仪观察分析熔覆层的宏观形貌、微观组织和物相,并利用显微硬度仪、磨损试验机测试熔覆层的显微硬度和耐磨性。研究结果表明:熔覆层由α-Mg和β-Mg17Al12组成,晶粒明显细化。采用低能量密度工艺即激光功率P=2 kW、扫描速度v=15 mm/s、激光能量密度E=26 J/mm2时,晶粒细化程度和β-Mg17Al12强化相综合强化效果最好,即显微硬度最高,为50 HV0.05～79 HV0.05比基体提高了13.64%～64.58%;耐磨性改善程度最好,磨损量是原始镁合金的40%,耐磨性提高60%。说明采用低能量密度且高功率快速扫描的工艺可以获得显微硬度和耐磨性改善程度最高的激光熔凝层。

In order to improve the wear resistance of AZ31B magnesium alloy, laser melted layer which had no crack and hole on AZ31B magnesium substrate was created by a 5 kW continuous wave CO2 laser with low density energy. The macrostructure, microstructure and phases were analyzed by means of optical microscope and X-ray Diffraction, the microhardness and abrasion performance were also tested with microhardness tester and abrasion testing instrument. The results showed that, the melted layers were mainly consisted of a-Mg and β-MglTAll2, and the grains of melted layer were smaller than that of base metal. With the technique of lower energy density laser which was P=-2 kW, v = 15 mm/s, E= 26 J/mm^2, the strengthening effect of fine-grain and β- Mgl7All2 was the best, the microhardness of laser melted layer was 50 HVO.05-79 HV0.05 which was improved by 13.64%- 64.58% and wear resistance was improved by 60% as compared to as-received AZ31B, the wear mass loss was 40% of as-received AZ31B. These showed that, the best laser melted layer with the best microhardness and wear resistance could be obtained by the technique of low density laser energy with high laser power and fast velocity.