激光熔覆CoCrFeNiWx高熵合金涂层的组织及性能

Microstructure and Properties of CoCrFeNiWx High Entropy Alloy Coated by Laser Cladding

目的研究W含量对激光熔覆CoCrFeNi高熵合金涂层组织及性能的影响。方法采用RFL-C1000光纤激光器在45#钢表面制备CoCrFeNiWx(x=0、0.2、0.4、0.6、0.8)高熵合金涂层,利用光学显微镜、X射线衍射仪(XRD)、扫描电子显微镜(SEM)、显微硬度计、摩擦磨损试验机等,对熔覆层的宏观形貌、微观组织、显微硬度和摩擦磨损性能进行分析和测试。结果熔覆层与基材之间的润湿性较好。随着W元素含量的增加,涂层由单一的FCC相转变为FCC相+μ相(Fe_(7)W_(6)、Co_(7)W_(6)),微观组织由胞状晶转变为树枝晶,晶粒尺寸减小,且在x=0.8时出现了明显的共晶组织和大量μ相沉淀。熔覆层的显微硬度随着W含量的增加而增大,x=0.8时,熔覆层具有最高的显微硬度,达到432.02HV0.3,约为基材硬度的2.1倍,为CoCrFeNi熔覆层硬度的2.2倍。x=0.6时,涂层磨损量最小,仅为CoCrFeNi涂层磨损量的30.85%,平均摩擦因数最低,约为0.311。随着W元素含量的增加,涂层磨损机制由黏着磨损和磨粒磨损转变为磨粒磨损。结论W元素的加入促进了μ相的生成,大幅提高涂层硬度,改善涂层的耐磨性能,强化机制为固溶强化、细晶强化和第二相强化。

CoCrFeNiWx(x=0,0.2,0.4,0.6,0.8)high entropy alloy coating was prepared on the surface of 45#steel by laser cladding.The effect of W content on the microstructure and properties of the high entropy alloy coating was studied.The 45#steel was cut into 50 mm×25 mm×10 mm and 50 mm×50 mm×10 mm steel plates to prepare single-pass cladding coating and multi-pass cladding coating,respectively.Remove the oxide scale of the substrate and clean the substrate,use JA2003 electronic precision balance to weigh the pure W powder and CoCrFeNialloy powder of different quality,and mix them according to different molar ratio.MSK-SFM-1 horizontal planetary ball mill was used to mix the alloy powder evenly,and the evenly mixed alloy powder was placed in a drying box for drying.RFL-C1000 fiber laser and prefabricated coating method were used for monolayer laser cladding experiment.Use electric spark wire cutting machine to cut the sample,use sandpaper to polish the sample step by step.D8 X-ray diffractometer was used to analyze the phase composition of samples.After etching the sample with saturated FeCl_(3)hydrochloric acid solution,HITACHI TM3030 scanning electron microscope(SEM)and energy dispersive spectrometer(EDS)were used to observe and test the microstructure and element distribution of the cladding coating.HV1000Z automatic rotary microhardness tester was used to test the microhardness of single channel cladding coating.The friction and wear tests of multi-channel cladding coating were carried out using M-2000 friction and wear testing machine.There is good wettability between cladding coating and substrate.With the increase of the content of W element coating for the FCC by single FCC phase transition phase+μ-phase(Fe_(7)W_(6) and Co_(7)W_(6)),the microstructure of cellular crystal into dendrites,grain size,grain arrangement more closely,and that there is an obvious when x=0.8 eutectic organization,grain boundary increases,intergranular produced a large number of combined interface,μ-phase carbide precipitation embedded at the same time.Provides a good support for the microstructure.The microhardness of the cladding coating increases with the increase of W content.When x=0.8,the cladding coating has the highest microhardness,reaching 432.02HV0.3,about 2.1 times of the hardness of the substrate,and 2.2 times of the hardness of the CoCrFeNi cladding coating.When x=0.6,the wear amount of CoCrFeNi coating is only 30.85% of that of CoCrFeNicoating,and the average friction coefficient is about 0.311.When x=0.8,the hardness of the coating is greatly improved and the plasticity is reduced due to the precipitation of a large number of μ-phase hard precipitates.In the process of friction and wear,more abrasive chips with high hardness are produced.These abrasive chips will be used as abrasive particles to micro-cut the surface of the coating,so that the friction coefficient of the coating increases to 0.315 when x=0.8.With the increase of W element content,the coating wear mechanism changes from adhesive wear and abrasive wear to single abrasive wear.The results show that the addition of W element promotes the formation of μ-phase.The hardness of the coating is greatly improved,and the wear resistance of the coating is improved.The strengthening mechanism is solid solution strengthening,fine grain strengthening and second phase strengthening.