Cr颗粒对Ni-Graphene复合沉积层组织结构及性能的优化

目的电沉积技术制备Ni-Cr-Graphene复合沉积层,调查不同Cr颗粒浓度对复合沉积层组织结构及性能的优化影响。方法利用电沉积技术在镍铝青铜(NAB)表面制备出Ni-Cr-Graphene复合沉积层。采用X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)与拉曼光谱仪(Raman),对复合沉积层的形貌、成分与组织结构(晶粒大小、结晶形状及结晶织构)进行表征,并采用显微硬度计与电化学工作站分别对沉积层的硬度及耐腐蚀性能进行调查。结果Graphene颗粒使得纯Ni沉积层中的Ni晶粒尺寸由175.3 nm减小到Ni-0Cr-4Graphene沉积层中的Ni晶粒尺寸60.5nm。随着Cr颗粒质量浓度进一步从0g/L增加到100 g/L,Ni-Cr-Graphene复合沉积层中的Cr质量分数从0%增加到23.8%,且Ni晶粒尺寸进一步减小到Ni-100Cr-4Graphene沉积层的29.1nm,Ni200]结晶织构被消除。Graphene与Cr颗粒显著提高了Ni-CrGraphene复合沉积层的表面硬度,所有复合沉积层的显微硬度均高于纯Ni沉积层(260.1HV0.2),且在100 g/L Cr颗粒浓度下,沉积层平均显微硬度为489.8HV0.2。同时Graphene与Cr颗粒改善了Ni-Cr-Graphene复合沉积层在3.5%NaCl溶液中的耐腐蚀性能,在100 g/L Cr颗粒浓度下,复合沉积层的自腐蚀电位(Ecorr)为-0.21 V,自腐蚀电流密度(Jcorr)为0.25μA/cm^2,其相对纯Ni沉积层Jcorr(7.01μA/cm^2)降低了1个数量级。结论溶液中Cr颗粒浓度的增加引起了Ni-Cr-Graphene复合沉积层中Cr含量的增加,使得更多Cr颗粒与Graphene颗粒共同作为Ni金属结晶形核点,促进了Ni的晶粒细化与织构转变,最终提高了复合沉积层的硬度与耐腐蚀性能。

Optimization Effects of Cr Additives on the Microstructure and Property of Ni-Graphene Composite Coatings

The Ni-Cr-graphene composite coatings were successfully synthesized by the electrodeposition technique.The effects of the Cr concentration on the microstructure and property of the Ni-Cr-graphene coatings were comprehensively investigated.The X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS)and Raman spectroscopy(Raman)were used to characterize the morphology,composition and microstructure(crystallite size,crystallite shape and texture)of the Ni-Cr-graphene coatings.A micro-hardness tester and an electrochemical workstation were used to evaluate the micro-hardness and corrosion behaviors of the Ni-Cr-graphene coatings,respectively.The results showed that with the co-deposition of 4 g/L graphene particles,the Ni crystallite size(175.3 nm)of the pure Ni coating was reduced to 60.5 nm of the Ni-0Cr-4 graphene coating.When the Cr concentration in electrolyte increased from 0 g/L to 100 g/L,the Cr content in Ni-Cr-graphene coating increased from 0 wt%to 23.8 wt%and the Ni crystallite size further decreased to 29.1 nm of the coating electrodeposited at Cr concentration of 100 g/L,and the Ni200]texture was gradually eliminated.The microstructure evolution contributed to the enhancement in surface micro-hardness of the coatings with increasing Cr concentration.The surface micro-hardness of the coating electrodeposited at Cr concentration of 100 g/L was 489.8HV0.2,which was much higher than that of the pure Ni coating(260.1HV0.2).Besides,the graphene and Cr particles improved the corrosion resistance of the Ni-Cr-graphene coatings in 3.5 wt%NaCl solution.The coating electrodeposited at 100 g/L Cr concentration possessed the best corrosion resistance with the maximum Ecorr(-0.21 V)and the minimum Jcorr(0.25μA/cm^2),which was reduced by an order of magnitude comparing to Jcorr of the pure Ni coating(7.01μA/cm^2).The enhancements in the micro-hardness and corrosion resistance of the Ni-Cr-graphene coatings were induced by the microstructure evolution of the Ni deposits.