激光能量密度对65Mn钢表面Ni60A/WC复合涂层摩擦磨损性能的影响规律

Effect of Laser Energy Density on Friction and Wear Properties of Ni60A/WC Composite Coating on 65Mn Steel Surface

目的改善旋耕刀65Mn钢的摩擦磨损性能,提高农机触土零部件的使用寿命。方法采用激光熔覆技术在65Mn钢基体表面制备Ni60A/WC复合涂层。通过改变激光功率调节激光能量密度,在不同能量密度下制备Ni60A/WC复合涂层,观察并测试不同参数下复合涂层试样的宏观形貌、微观结构、物相组成、元素分布、显微硬度及摩擦磨损特性,研究激光能量密度对Ni60A/WC复合涂层组织演变及摩擦磨损性能的影响规律和机理。结果Ni60A/WC复合熔覆层顶部主要有胞状晶和树枝晶,分布较紧密,熔覆层中部主要有树枝状晶,熔覆层底部主要为胞状晶和垂直交界面生长的枝晶,且分布均匀致密。随着激光能量密度的升高,熔覆层的熔高和熔深增加显著,WC硬质相颗粒发生分解,硬质相的数量明显减少,涂层的平均显微硬度降低。在激光能量密度为120 J/mm^(2)时,熔覆层的平均显微硬度为587.1HV1.0,相较于基体,提升了约1.8倍。此时熔覆层的平均摩擦因数最小,为0.312,相较于基体,得到显著提升,摩擦磨损机制为轻微的磨粒磨损。经田间试验测试发现,在激光能量密度为120 J/mm^(2)时制备的带有熔覆层的旋耕刀相较于无熔覆层的旋耕刀,其磨损质量降低了63%。结论通过控制激光能量密度,可以有效调控Ni60A/WC熔覆层的硬度和耐磨性,可为农机触土易磨损件的减摩耐磨表面强化改性提供理论指导。

A rotary tiller is a commonly used device in farming work.Its main soil-engaging parts,rotary blades,mainly undergo low-stress abrasive wear when working in the soil.As the wear increases,it leads to the failure of rotary blades.Every year,each country wastes a lot of steel.In order to improve the friction and wear properties of 65Mn steel used in rotary blades,improve the service life of soil-engaging parts of agricultural machinery,extend their service time,and reduce the waste of steel.Ni60A/WC composite coatings were prepared on the surface of 65Mn steel by laser cladding technology.The Ni60A/WC composite coatings were prepared under different laser energy densities by changing the laser power to adjust the laser energy density by selecting the appropriate scanning speed,powder feeding amount,spot diameter,overlap rate,and other process parameters through pre-experiment.The macroscopic morphology,crack distribution,microstructure,phase composition,element distribution,microhardness,and friction and wear characteristics of the composite coating samples under different parameters were observed and tested.The influence law and mechanism of laser energy density on the microstructure evolution and friction and wear properties of Ni60A/WC composite coatings were studied.The results showed that when the laser energy density was low,there were convex defects in the center of each cladding layer,and there were many penetrating cracks on the surface of the cladding layer.With the increase of laser energy density,the surface of the cladding layer gradually became smooth and flat,and the cracks gradually disappeared.Microscopically,the top of the Ni60A/WC composite cladding layer mainly had cellular crystals and dendrites and was closely distributed.There were mainly dendritic crystals in the middle of the cladding layer.The bottom of the cladding layer was mainly cellular crystals and dendrites growing perpendicular to the interface,and they were uniform and dense.With the increase of laser energy density,the melting height and melting depth of the cladding layer increased significantly,the WC hard phase particles decomposed,the number of hard phases decreased significantly,and the average microhardness of the coating decreased.When the laser energy density was 120 J/mm^(2),the average microhardness of the cladding layer was 587.1HV1.0,which was about 1.8 times that of the substrate.At this time,the average friction coefficient of the cladding layer was 0.312,which was significantly lower than that of the substrate.The hardness and wear resistance were significantly improved,and the friction and wear mechanism was slightly abrasive wear.The rotary blade with cladding layer was prepared by laser cladding technology when the laser energy density was 120 J/mm^(2).The field test showed that the wear quality of the rotary blade with a cladding layer was 63%lower than that of the rotary blade without a cladding layer.The rotary blade prepared by laser cladding technology had better cost performance.The hardness and wear resistance of the Ni60A/WC cladding layer can be effectively controlled by controlling the laser energy density.This study can provide theoretical guidance for the anti-friction and wear resistance and surface strengthening modification of agricultural machinery soil-touching parts.