NdFeB表面磁控溅射沉积Ti/Al多层膜的结构及耐腐蚀性能

采用直流磁控溅射技术在烧结NdFeB磁体表面沉积Ti/Al多层膜,并研究其结构及在NaCl溶液中的耐腐蚀性能。在Ti/Al多层膜中,Ti层为密排六方结构,成功打断了Al层(面心立方结构)的柱状晶结构生长。与纯Al膜相比,Ti/Al多层膜具有更致密的表面,且周期数增加,表面越平整致密。动电位极化曲线结果发现,纯Al膜试样的自腐蚀电流密度为1.9×10-5 A/cm-2左右,5周期Ti/Al多层膜试样的自腐蚀电流密度约为1.1×10-7 A/cm2,比纯Al膜小近两个数量级,且随着多层膜周期数的增加,其腐蚀电流密度进一步减小。这些结果表明在快速且破坏性强的腐蚀情况下,Ti/Al多层膜抗腐蚀能力比纯Al膜好,且随着周期数的增加进一步提高。NaCl溶液中长期腐蚀试验时,Ti/Al多层膜的耐腐蚀性能不如纯Al膜,这可能是由Ti层和Al层间形成原电池且多层膜应力较大导致。

Structure and Corrosion Resistance of Ti/Al Multilayers Coated on NdFeB Magnets by Magnetron Sputtering

Ti/Al multilayers were deposited on sintered NdFeB magnets by direct current magnetron sputtering. The structure and corrosion resistance of Ti/Al multilayers in a NaCl solution were studied. Ti layers with a hexagonal close packed structure were obtained in the Ti/Al multilayers. The columnar structure growth of Al layers was successfully interrupted by the intercalated Ti layers. The Ti/Al multilayers showed more compact surfaces than the Al single layer, and the more compact and smooth the surface are, the more the number of bilayer period is. For the NdFeB specimen coated with Al single layer, the corrosion current density was approximately 1.9×10^-5 A/cm². The corrosion current density of 5-period Ti/Al multilayer was approximately 1.1×10^-7 A/cm², about two orders of magnitude lower than that of the Al single layer. With decreasing bilayer period, the corrosion current density further decreased. These findings show that the Ti/Al multilayers present better resistance to the fast and destructive corrosion than the Al single layer and show further improved resistance with decreasing bilayer period. However, the longterm corrosion resistance of Ti/Al multilayers is inferior to that of the Al single layer, which may be ascribed to the combined effects of galvanic corrosion and high stress.