激光能量密度对激光熔覆NiCoCrAlY涂层组织与性能的影响

为探究激光熔覆过程中能量密度对NiCoCrAlY涂层组织与性能的影响，在304不锈钢表面制备了NiCoCrAlY涂层。利用X射线衍射仪、扫描电子显微镜分析了NiCoCrAlY涂层的相组成和微观组织。通过显微维氏硬度计和往复摩擦磨损试验机研究了NiCoCrAlY涂层的硬度和耐磨性能。结果表明：NiCoCrAlY涂层气孔数量随激光能量密度增大而减少，熔深和熔高随激光能量密度增大而增大，当激光能量密度为3.8 kJ/cm²时涂层稀释率最低，同时气孔数量较少。NiCoCrAlY涂层中包含γ/γ′相和β相，微观结构以柱状晶为主，随着激光能量密度的增大，β相含量升高，柱状晶变大。不同激光能量密度下NiCoCrAlY涂层硬度均高于基体，当激光能量密度为3.8 kJ/cm²时 涂层硬度最高，为301 HV_0.2. 在往复摩擦磨损实验中，当激光能量密度为3.8 kJ/cm²时 NiCoCrAlY涂层摩擦系数最小为0.46，磨损体积最少为0.235 9 mm³，磨损机理主要为磨粒磨损，耐磨性能最好。

Effect of Laser Energy Density on Microstructure and Properties of Laser Cladding NiCoCrAlY Coating

NiCoCrAlY coating was prepared on the surface of 304 stainless steel in order to study the effect of energy density on the microstructure and properties of NiCoCrAlY coating during laser cladding. The phase composition and microstructure of NiCoCrAlY coating were analyzed by X-ray diffractometer (XRD) and scanning electron microscope (SEM). The hardness and wear resistance of NiCoCrAlY coating were studied by using a micro Vickers hardness tester and reciprocating friction and wear testing machine. The results show that the number of pores in NiCoCrAlY coating decreases with the increase in laser energy density, and the penetration and melting height increase with the increase in laser energy density. When the laser energy density is 3.8 kJ/cm², the coating dilution rate is the lowest, and the number of pores is less. The NiCoCrAlY coating contains γ/γ′ phase and β phase, and its microstructure is mainly columnar crystals. As the laser energy density increases, β phase content increases and the columnar crystals become larger. The hardness of NiCoCrAlY coating is higher than that of the substrate at different laser energy densities. The coating hardness is the highest when the laser energy density is 3.8 kJ/cm², which is 301 HV_0.2. In the reciprocating friction and wear experiment, when the laser energy density is 3.8 kJ/cm², the friction coefficient is the smallest (0.46) and wear volume is the smallest (0.235 9 mm³), the wear mechanism is mainly abrasive wear, and the wear resistance is the best.