扫描速率对激光熔覆层组织及耐蚀性的影响

Effect of laser scanning speeds on the microstructure and corrosion resistance of laser cladding layers

为了研究激光扫描速率对镍基熔覆层组织及耐蚀性能的影响,采用喷涂预置涂层与不同扫描速率下激光重熔工艺在Q235低碳钢表面制备了镍基合金熔覆层,利用光学显微镜与扫描电镜对熔覆层表面宏观形貌和微观组织形貌进行了观察,利用显微硬度计和电化学腐蚀法对熔覆层显微硬度与耐蚀性进行了测定与分析。结果表明,其它条件不变,随着激光扫描速率的增加,熔覆层组织更加致密、均匀,晶粒愈发细小,并且白亮枝晶增多,枝晶间的共晶减少;由于晶粒细化等作用,使得熔覆层的平均显微硬度与耐蚀性能均得到了显著提高;其中,以激光功率为3kW、扫描速率为6mm/s、光斑直径为3mm等参量下得到的熔覆层组织及性能最优。这些结果对合理选取激光熔覆工艺参量以达到最佳熔覆效果是有帮助的。

Ni-based alloy coating was prepared on the Q235 steel by thermal spraying and laser remehing process at different scanning speeds, in order to study the effect of laser scanning speeds on the microstructure and corrosion resistance of laser cladding layers. The surface macro-morphology and mierostructure were observed with an optical microscope （OM） and a scanning electronic microscope （SEM） , and the micro-hardness and corrosion resistance were measured and analyzed with the hardness tester and electrochemical corrosion method. The results show that the microstructure becomes dense and even and the grains become tiny, while the amount of the white-bright dendrites increase and the eutectic compounds between the dendrites reduce with laser scanning speeds increasing. In addition, the micro-hardness and corrosion resistance greatly increase due to grain refinement and so on. As a result, the optimum technological parameters are 3kW in laser power, 6mm/s in laser scanning speed and 3mm in beam diameter for the Ni-based alloy cladding layer preparation. The result is expected to provide practical value for selecting reasonable laser cladding technological parameters to achieve optimal performance of the cladding layer.