摘要
利用直流复合电镀方法将WC纳米颗粒均匀分散到Ni镀层,用微米压痕仪测试了镀层的力学性能,用动电位极化曲线研究了镀层在pH=9.0的0.05 mol/L H_3BO_3+0.075 mol/L Na_2B_4O_7缓冲溶液中的电化学性能.结果表明,与纯Ni镀层相比,纳米复合镀层的晶粒尺寸显著减小,约为21 nm;硬度提高了81%,达到651 HV;自腐蚀电流密度降低约一个数量级,约为1.29×10^(-7)A/cm^2;破钝电位基本一致,但致钝电位(10 mV)更低,维钝电流密度(1.79×10^(-6)A/cm^2)更小,仅为纯Ni镀层的1/7.利用Mott-Schottky理论结合点缺陷模型分析表明:表面钝化膜仍具有p型半导体特征,WC纳米颗粒显著降低基体Ni的晶粒尺寸,引起钝化膜中点缺陷密度和扩散系数的降低.
The metallic matrix composite with ceramic nano-particles has a wide prospect in many applications due to its superior properties. The nanocomposite Ni-WC coating has been synthe- sized by using DC co-electrodeposition of Ni with WC nano particles. Its hardness was measured by using ultra-micro hardness tester. Its corrosion and passive properties were investigated in 0.05 mol/L H3BO3＋0.075 mol/L Na2B407 buffer solution with pH--9.0 by using potentiodynamic polarization measurement. As compared to pure nanocrystalline （nc） Ni, nanoeomposite refined remarkably, with average grain size about 21 nm and the hardness increase of 80%, reaching about 651 HV. The corro- sion current density icorr is 1.29 × 10-2 A/cm2, approximately one magnitude order lower than that of nc Ni. With the similar passive film breakdown potential, nanocomposite exhibits a lower passivation potential Ep of 10 mV and a much lower passive current density ip of 1.79×10-6 A/cm2, about 1/7 that for nc Ni. According to the Mott-Schottky analysis together with point defect model, the passive film on the nanocomposite exhibits p-type semi conducting behavior, similar to that on the nc Ni. The urain refinement of Ni is beneficial to the reduction of both the donor density and diffusion coefficient.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第10期1185-1190,共6页
Acta Metallurgica Sinica
基金
辽宁省自然科学基金项目201202127
辽宁省高等学校杰出青年学者成长计划项目LJQ2011033资助~~
