稀土对Ni-P化学镀层组织结构及性能的影响

Effect of Rare Earth on Microstructure as well as Wear Resistance and Corrosion Resistance of Electroless Ni-P Coating

过去,对稀土在化学镀镍中的作用研究不够系统。在Ni-P基础化学镀液中添加3种稀土离子Y3+,Nd3+,La3+制备了Ni-P化学镀层。利用电感耦合等离子质谱仪、X射线衍射仪、扫描电子显微镜、显微硬度计、磨损试验机等考察了稀土对镀层组织结构、显微硬度、耐磨及耐蚀性的影响。结果表明:添加稀土后,镀层仍为非晶态结构,镀层内磷含量大幅提高,稀土有效细化了镀层组织,镀层表面形貌变得更加平整、致密、均匀;镀层的显微硬度、耐磨性和耐蚀性也得到不同程度的提高;在3种稀土中,Y3+的作用最显著,当其在镀液中的浓度为0.04 g/L时,镀层显微硬度达最大值606 HV,同时磨损量为最低值4.957 2 mg,而镀层在10%H2SO4溶液中的腐蚀速率则低至0.006 4 mg/(cm2.h)。

Three kinds of rare earth ions(Y3+,Nd3+,La3+) were separately introduced into electroless NP plating bath to prepare rare earthdoped electroless NiP alloy coating.The microstructure and phase composition of asprepared NiP alloy coating were analyzed by means of electric coupled plasma mass spectrometry,Xray diffraction and scanning electron microscopy,while the hardness and wear resistance were evaluated with a microhardness meter and a friction and wear tester.Moreover,the corrosion rate of the coating was measured.Furthermore,the effect of rare earth ions on the microstructure and performance of asprepared NiP alloy coating was investigated.It was found that NiP alloy coating obtained in the presence of the rare earth ions still retained amorphous structure,but the P content was significantly increased.Besides,rare earth ions helped to refine the structure of the NiP alloy coating and increase the microhardness,wear resistance and corrosion resistance of the coating to varying extents,leading to smooth,compact and uniform NiP alloy coating.Particularly,Y3+ was the most effective in improving the structure as well as wear resiastnce and corrosion resistance of electroless NiP alloy coating.Namely,the NiP alloy coating obtained from the electroless NiP plating bath containing 0.04 g/L Y3+ had the maximum microhardness of 606 HV and the minimum wear mass loss of 4.957 2 mg,while its corrosion rate in 10% H2SO4 solution was reduced to 0.006 4 mg/(cm2·h).