扫描速度对激光熔覆Al基非晶复合层组织与性能的影响

目的在5083铝合金表面激光熔覆制备Al-Ni-Y-Co-La非晶复合熔覆层,并研究扫描速度对熔覆层组织与性能的影响规律。方法采用YAG:Nd激光器,在扫描速度分别为200、300、400 mm/min下制备Al基非晶复合层,并采用金相显微镜、扫描电子显微镜、X射线衍射仪、硬度仪、摩擦磨损试验机观察熔覆层微观组织及测试其显微硬度及耐磨损性能。结果熔覆层主要由α-Al相、Al3Y及Al4Ni Y等金属化合物相组成。随着扫描速度的增加,熔覆层组织由粗大的条(柱)状晶向细小的等轴晶转变,当扫描速度大于300 mm/min时,熔覆层内存在部分非晶复合区域。熔覆层平均显微硬度大于250HV0.1,当扫描速度为300 mm/min时,熔覆层显微硬度最高达300HV0.1。低载荷下,扫描速度为200、300、400 mm/min时的熔覆层和基体的平均摩擦系数分别为0.384、0.288、0.304、0.571,平均磨损体积分别为7.586×10~7、2.516×1~07、5.027×10~7、45.638×10~7μm3,熔覆层平均摩擦系数和磨损体积较5083基体均显著降低。结论采用激光熔覆技术能够制备Al基非晶复合层。当扫描速度为300 mm/min时,熔覆层具有最佳的成形性和耐磨损性能;当扫描速度进一步增大至400 mm/min时,熔池拖带基体翻卷上浮导致成分严重偏析,使熔覆层的成形性和耐磨损性能下降。

The Effect of Scanning Speed on Structure and Performance of Al-based Amorphous Composite by Laser Cladding

ABSTRACT:Objective To fabricate Al-Ni-Y-Co-La amorphous composite claddings on 5083 substrates by laser cladding, and study the effects of laser scanning speed on microstructure and performance of the cladding.Methods YAG:Nd laser was used to fabricate Al-based amorphous composite claddings at the speed of 200, 300, 400 mm/min. OM, SEM, XRD, hardness tester and friction wear testing machine were used to observe the microstructure and test the microhardness and wear resistance of claddings. ResultsThecladding mainly consistedof α-Al, Al3Y, Al4NiY and other metallic compound phases. With the in- crease of scanning speed, the grain structure changed from the coarse banded crystal to the minor isometric crystal. When the laser scanning speed was over 300 mm/min, there was a partial amorphous phase. The average microhardness of the cladding was greater than 250HV0.1. When the scanning speed was 300 mm/min, the biggest microhardness of the cladding reached 300HV0.1. The average friction coefficient of cladding and substrate at low load when scanning speed was 200, 300, 400 mm/min was 0.384, 0.288, 0.304 and 0.571, and the corresponding average wear volume was 7.586×107, 2.516×107, 5.027×107, 45.638×107μm3. The claddings showed very lower friction coefficient and wear volume than 5083 substrate.Conclusion Al-based amorphous composite claddings can be fabricated by laser cladding. When the laser scanning speed is about 300 mm/min, the cladding has the best formability and wear resistance. While the scanning speed further increases to 400 mm/min, the molten pool will towing substrate rewinding and floating, which leads to the severe segregation of the cladding and decrease its formability and wear resistance.