海工机械Ni-Co/SiC纳米复合镀层微观结构及耐蚀性能

Microstructure and Corrosion Resistance of Ni-Co/SiC Nanocomposite Coating for Marine Machinery

采用扫描电子显微镜(SEM)、能谱分析(EDS)和X射线衍射(XRD)研究了纳米SiC颗粒对Ni-Co镀层结构和形貌的影响,通过EIS,Tafel电化学方法探究了Ni-Co/SiC电沉积过程及镀层的电化学腐蚀性能。结果表明,Co的加入使Ni镀层晶粒细化,孔隙率降低,并使部分结构非晶化,耐蚀性提高。纳米SiC颗粒具有促进Ni-Co合金形核长大和提高其硬度的双重作用,使Ni-Co/SiC耐磨性增强,与Ni-Co合金相比其E_(corr)更正,i_(corr)更小,R_c更大,具有优异的耐蚀性和耐磨性。Ni-Co/SiC具有更好的服役稳定性,而Ni-Co合金服役中耐蚀性降低较快。在服役过程中,镀层腐蚀过程经历了3个阶段:即浸润阶段;电解液在涂层中传输的扩散控制阶段;电解液到达基材表面后扩散速率已大于电化学速率的电化学控制阶段。Ni-Co/SiC合金具有良好的耐磨耐蚀性能,在海水多重因素交互作用下能够对海工机械提供长效防护,在海工防护领域具有良好的应用前景。

The effects of SiC nanoparticles on the structure and morphology of Ni-Co coating were investigated by scanning electron microscopy （SEM）, energy spectrum analysis （EDS） and X-ray diffraction （XRD）. The influences of SiC nanoparticles on Ni-Co composite electrodeposition process and the electrochemical corrosion properties of Ni-Co/SiC composite coatings were studied by EIS and Tafel methods. The results show that the addition of Co2＋ ions refines the grains of the Ni coating, reduces the porosity, transforms some structure to amorphous and improves the corrosion resistance. SiC nanoparticles can promote the nucleation and growth of Ni-Co alloy and improve the hardness of the alloys. Compared with Ni-Co alloys, Ni-Co/SiC coatings have excellent corrosion and wear resistance, which have more positive E lower i and larger Re. The Ni-Co/SiC composite coatings have the better stability of service performance, while the corrosion resistance of Ni-Co alloy decreases fast in 3.5 wt% NaC1 solution. The process of corrosion experiences three stages, namely a wetting stage, a diffusion control stage in which electrolyte transports in the coating and an electrochemical control stage in which diffusion rate is larger than the electrochemical rate after electrolytes reach the substrate surface. Ni-Co/SiC alloys can provide long-term protection of marine engineering machinery under the influence of multifactors interaction in seawater environment.