Parylene镀层对烧结Nd-Fe-B磁体稳定性的影响

Effects of Parylene coating on the stability of sintered Nd-Fe-B magnets

采用化学气相沉积法(CVDP)在Nd-Fe-B磁体和电镀Cu层的Nd-Fe-B磁体表面包覆派瑞林(Parylene)镀层,分析Parylene镀层和Parylene+电镀Cu复合镀层对磁体化学稳定性和温度稳定性的影响。Parylene分子沉积到磁体表面形成一层致密的镀层,镀层表面形成大小不同的颗粒,造成磁体表面粗糙度变大。Parylene镀层与Nd-Fe-B基体结合紧密,未出现缝隙和镀层脱落现象,镀层厚度随Parylene粉末质量增加逐渐增大。Parylene镀层一方面可以有效改善Nd-Fe-B磁体的化学稳定性,提高磁体中性盐雾耐腐蚀性能;另一方面对磁体有很好的抗热氧化保护作用,有利于提高磁体的温度稳定性,降低高温磁通不可逆损失(h_(irr))。Cu镀层的存在不利于Parylene镀层改善磁体化学稳定性和温度稳定性,这是由于电镀Cu层与Nd-Fe-B磁体基体和Parylene镀层结合不紧密,界面存在缝隙与裂痕。

In this paper,Parylene coating is deposited on the surface of sintered Nd-Fe-B magnet with/without electroplated Cu layer by chemical vapor deposition polymerization(CVDP) method,and effects of Parylene coating and Parylene+electroplating Cu composite coating on the chemical and temperature stability of Nd-Fe-B magnets are investigated.Parylene molecules deposite on Nd-Fe-B surface to form a dense coating,which consists of Parylene particles with different sizes and results in an increase of surface roughness.Parylene coating contacts with the Nd-Fe-B substrate closely and there is no gap and coating peeling off at the interface.The coating thickness gradually increases with the vapordeposited Parylene powders.The Parylene coating,on one hand,can effectively increase the chemical stability of Nd-Fe-B magnets and improve the corrosion resistance of the magnets in neutral salt spray.On the other hand,it also has good antithermal oxidation protection effect,which is beneficial to improve the temperature stability and reduce the high temperature magnetic flux irreversible loss(h_(irr)).The electroplated Cu layer is not conducive to improve the chemical stability and temperature stability of Nd-Fe-B magnets by depositing Parylene coating,which is because of the gaps and cracks at the interface that come from the not close contact of Parylene coating with the electroplated Cu layer and the Nd-Fe-B matrix.