高碳化硅含量的镍–钨–微米碳化硅复合电镀及其耐蚀性

Electroplating of nickel–tungsten–micron-silicon carbide composite with high content of silicon carbide and its corrosion resistance

采用电沉积法在铁片上制备Ni–W–微米SiC复合镀层。研究了微米SiC颗粒用量、pH、电流密度等工艺参数对复合镀层中SiC颗粒含量的影响,得到最优工艺为:NiSO_4·6H_2O 20 g/L,Na_2WO_4·2H_2O 50 g/L,Na_3C_6H_8O_7·2H_2O 50 g/L,微米SiC颗粒20g/L,pH7.0,电流密度2.5 A/dm^2。采用X射线衍射仪、扫描电子显微镜、能谱仪和浸泡腐蚀试验表征了Ni–W–微米SiC复合镀层的晶相结构、表面形貌、元素组成和耐蚀性。采用红外光谱法初步探讨了SiC微米颗粒的沉积机理。结果表明,SiC微米颗粒在复合镀层中的质量分数可高达42.5%,SiC微米颗粒的存在能消除Ni–W合金镀层的裂纹,从而提高镀层对基体的保护能力。镀液中的阴离子可能对SiC微米颗粒的沉积过程有一定的影响。

Ni-W-micron-SiC composite coating was prepared on iron substrate by electrodeposition. The effects of process parameters including dosage of micron SiC particles, pH and current density on the content of SiC particles in composite coating were studied. The optimal process parameters were obtained as follows： NiSO4·6H2O 20 g/L, Na2WO4·2H2O 50 g/L, Na3C6H8O7·2H2O 50 g/L, micron SiC particles 20 g/L, pH 7.0 and current density 2.5 A/dm2. The crystalline phase structure, surface morphology, elemental composition and corrosion resistance of Ni-W-micron-SiC composite coating were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy and immersion corrosion test, respectively. The deposition mechanism of micron SiC particles was preliminarily discussed by infrared spectroscopy. The results indicated that the content of micron SiC particles in composite coating reaches 42.5wt%. The cracks of Ni-W alloy coating can be eliminated possibly due to the existence of micron SiC particles, improving the protection capability of composite coating for matrix. Anions in plating bath may have certain effects on the deposition process of micron SiC particles.