激光熔覆工艺参数对MoFeCrTiWAlNb高熔点高熵合金涂层组织和性能的影响

Effects of Laser Cladding Process Parameters on Microstructure and Properties of MoFeCrTiWAlNb High-Melting-Point and High-Entropy Alloy Coating

为了提高工具钢的重复使用寿命,通过激光熔覆技术在高速钢表面成功制备了MoFeCrTiWAlNb高熔点高熵合金涂层,利用金相显微镜(OM)、X射线衍射仪(XRD)、扫描电镜(SEM/EDS)、显微硬度计等设备,探究了激光功率、激光扫描速率对高熵合金涂层显微组织和硬度的影响规律。结果表明:当激光功率较小时,熔覆层较浅,熔覆层表面出现起球、孔洞等缺陷;随着激光功率的增加,涂层表面形貌更加平整均匀,涂层显微组织由胞状枝晶和颗粒状组织组成,涂层显微硬度先增加后减小。随着激光扫描速率的增加,熔覆层成型质量变差,但涂层组织更加细小均匀,涂层显微硬度逐渐提高。较优的工艺参数为激光功率2.6 kW、扫描速率4 mm/s。

In order to improve the repetitive service life of tool steel,the MoFeCrTiWAlNb high-melting-point and high-entropy alloy(HEA)coating was successfully fabricated on the surface of high-speed steel by laser cladding.Metallographic microscope(OM),X-ray diffractometer(XRD),scanning electron microscope(SEM/EDS),and microhardness tester were used to investigate the effects of laser power and laser scanning speed on microstructure and hardness of the high-entropy alloy coatings.Results showed that the laser cladding layer was shallower and there existed a few defects such as pilling and holes on the surface of the cladding layer when the laser power was low.With the increase of the laser power,the surface morphology of the coating became smooth and uniform,the microstructure of the coating was composed of the cellular dendrites and the granular structures,and the microhardness of the coating was first increased and then decreased.As the laser scanning speed increased,the forming quality of the cladding layer became worse,but the coating structure became finer and more uniform and the microhardness of the coating was increased gradually.The optimized laser parameters were as follows:lase power 2.6 kW and scanning speed 4 mm/s in this experiment.