锌系磷化膜对钕铁硼/Ni-P镀层结合力的影响

Effect of Zn Phosphating Film for NdFeB Magnet on Adhesive Strength of Ni-P Coating

针对工业化生产中烧结NdFeB磁体与Ni-P化学镀层结合力差的问题,尝试在磁体表面制备一层磷化膜,以提高Ni-P镀层与基体的结合力。通过正交实验确定了磷化液的组成及工艺,利用扫描电镜分析了磷化膜表面形貌的演变规律,并讨论了表面形貌对镀层结合力的影响机制。结果表明,磷化处理后的磁体表面与Ni-P镀层的结合力由2.33 MPa提升到10.07 MPa,其原因是磷化膜表面大量均匀的微裂纹对Ni-P镀层的机械钉扎作用。

As a usual protecting technique,Ni-P coatings have a short service life in industrial application for it poor adhesion with sintered NdFeB magnets.In this work,a kind of Zn phosphate film was fabricated on NdFeB sintered magnets surface to enhance the adhesion strength between the Ni-P coating and the substrate.Phosphating solution composition and process were determined by orthogonal experiment.The morphology evolution rule of phosphate film was revealed-using SEM analysis.The relationship between the adhesion strength mechanism and the morphology of Zn phosphate film was also discussed.The results show that the adhesion strength between magnet surface and Ni-P coating is enhanced from 2.3 MPa to 10.1 MPa after Zn phosphating treatment.The significant enhancement of the adhesion strength is mainly due to the mechanical pinning effect between Ni-P coating and phosphate film which have a large number of uniform microcracks on its surface.