烧结工艺对瓦特镍镀层抗腐蚀性能的影响

Effect of sintering process on corrosion resistance of Watt nickel coating

采用OLYMPUS光学金相显微镜和扫描电镜(SEM)分析了瓦特镍镀层的显微形貌;采用CHI 650E型电化学工作站测试了不同烧结工艺下瓦特镍镀层在3.5%NaCl溶液中的阳极极化曲线。结果表明:(1)镀后烧结温度越高,镀层越厚,镀层晶粒越粗大,晶界越少;(2)840℃烧结后镀层分层最明显,白亮层厚度约为3.52μm,扩散层厚度约3.35μm。920℃烧结后镀层分层减弱,白亮层厚度约为4.98μm,扩散层厚度约为1.20μm;(3)镀后烧结温度越高,镀镍层抗腐蚀性能越好,自腐蚀电位越高,由沉积态的-480mv增长至840℃和920℃烧结后的-450mv、-410mv。因此,4J29合金瓦特镍镀层经高、低温烧结后,抗腐蚀性能略有提升,满足外壳使用要求。

The morphology of Watt nickel coating was analyzed by OLYMPUS optical microscope and SEM;The anodic polarization curves of Watt nickel coatings with different sintering processes in 3.5%NaCl solution were measured by CHI 650E electrochemical workstation.Results show that:1)the higher the sintering temperature after plating,the thicker the coating,the larger the grain size,the less the grain boundaries;2)Coating layer consists of 3.52μm thick white bright layer and 3.35μm thick diffusion layer sintered at 840℃while stratification of the coating is weakened which consists of 4.98μm thick white bright layer and 1.20μm thick diffusion layer sintered at 920℃;3)The higher the sintering temperature after plating,the better the corrosion resistance of nickel coating,the higher the corrosion potential rised from-480mv in sedimentary state to-450mv at 840℃sintering and-410mv at 920℃sintering.Corrosion resistance of 4J29 alloy Watt nickel coating was improved slightly and meet the requirements of shell after high and low temperature sintering.