激光粉末定向能量沉积AlCoCrFeNi高熵合金涂层的工艺、组织与力学性能

Processes,microstructures and mechanical properties of AlCoCrFeNi high entropy alloy coatings prepared by laser powders directed energy deposition

采用激光粉末定向能量沉积技术制备AlCoCrFeNi高熵合金涂层,研究了激光功率、扫描速率及搭接率等工艺参数对涂层成形特性、组织及力学性能的影响规律。研究结果表明,随着激光功率的增加,单道涂层的熔宽增大,而余高和熔深先增大后减小。随着扫描速率的增加,熔宽、余高和熔深均出现不同程度的降低。随着搭接率的升高,稀释现象逐渐减弱。搭接率为33%和50%的沉积层组织以等轴晶为主,而搭接率为67%的沉积层组织以枝晶为主。激光定向能量沉积的高G/R及二次退火效应造成了多道涂层存在亚晶结构。AlCoCrFeNi涂层大幅提升了Q235基材的表面硬度,硬度从167(HV)增加到500(HV)以上。搭接率为50%的涂层硬度最高,超过550(HV)。多道涂层的低稀释效应和独特的微观组织使其硬度明显高于单道涂层的硬度。为了兼顾成形效率和低稀释率,可选用激光功率为2200 W、送粉速率为10 mm/s和搭接率为50%的工艺条件制备AlCoCrFeNi高熵合金涂层。

AlCoCrFeNi high-entropy alloys coatings were prepared by laser powders directional energy deposition technology,and the influence of process parameters such as laser power,scanning rate and lap rate on the forming characteristics,microstructures and mechanical properties were investigated.The results show that with the increase of laser power,the melt width of single-pass coating increases,while the residual height and depth of melt firstly increase and then decrease.The melt width,residual height and depth of melt decrease to different degrees with the increase of scanning rate.The dilution phenomenon decreases with the increase of overlap rates.The coatings deposited by the overlap rates of 33%and 50%are dominated by equiaxed crystals,while the coating of 67%overlap rate is dominated by dendrites.The high G/R and the secondary annealing effect of the laser directed energy deposition result in the formation of sub-crystalline structures in multi-pass coatings.The multi-pass AlCoCrFeNi coatings significantly enhance the surface hardness of the Q235 substrate,with the hardness increasing from 167(HV)to more than 500(HV).The highest hardness of over 550(HV)is achieved for the 50%overlap rate coating.Moreover,the low dilution effect and unique microstructure of the multi-pass coating result in a significantly higher hardness than that of the single-pass coating.Balancing forming efficiency and low dilution rate,the laser power of 2200 W,powder feeding rate of 10 mm/s and 50%overlap rate can be used as the optimal process parameters to prepare AlCoCrFeNi high-entropy alloys coatings.