电沉积金属Ni涂层的高温腐蚀性能

Hot corrosion performance of Ni electrodeposited coatings

通过调控电沉积过程中的阴极电流密度制备具有不同晶粒尺寸和择优取向的Ni镀层。采用透射电镜(TEM)、扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)对高温腐蚀前、后不同Ni镀层进行检测分析,对比研究不同Ni镀层经过960℃的78.07%Na3AlF6-9.5%AlF3-5%CaF2(质量分数)熔盐气氛腐蚀后的结构、成分和形貌。结果表明:在高电流密度下易获得晶粒细小,平均晶粒尺寸为120nm,具有较强<100>择优取向的Ni镀层;而在低电流密度下所得的Ni镀层晶粒较粗大,平均晶粒尺寸为925nm,具有较弱的<111>择优取向。在腐蚀气氛下,低电流密度下所得的Ni镀层在高温腐蚀后有利于生成晶粒粗大、且具有完整"八面体"结构的NiAl2O4尖晶石相;而高电流密度下所得Ni镀层表层腐蚀层的晶粒细小,且主要为NiO相。

Ni coatings with different grain sizes,preferred orientation and impurity element contents can be electrodeposited by regulating cathode current density. Using transmission electron microscopy（TEM）,scanning electron microscopy （SEM）,energy dispersive spectroscopy （EDS） and X-ray diffractometry（XRD）,the oxide film structures,composition and morphology of Ni coatings before and after being corroded in corrosive atmosphere of 78.07%Na3AlF6-9.5%AlF3-5%CaF2 （mass fraction,%） were investigated comparatively at 960 ℃. The results show that Ni coatings with smaller grains and a strong 100 preferred orientation are easily obtained under higher current density. While Ni coatings deposited under lower current density have coarser grains and a weak 111 preferred orientation. In the corrosive atmosphere,Ni coating prepared with a lower current density is benefit to the formation of dense NiAl2O4 spinel phase on the surface layer,while NiO is the major phase on the surface of oxide film after the corroding Ni coating prepared with a high current density.