不同方式电沉积Ni-纳米TiC复合镀层的微观结构与性能

Microstructure and properties of Ni-nano TiC composite coating prepared by different electrodeposition methods

  • 摘要: 为改善电沉积Ni-纳米TiC复合镀层的质量,利用电沉积技术在Q235钢表面制备出Ni-纳米TiC复合镀层,对比分析了直流、单脉冲和双脉冲三种不同电沉积方式对复合镀层的微观组织与表面性能的影响。通过SEM/EDS分析镀层的表面形貌和元素分布,利用XRD研究镀层的物相和估算晶粒大小,分别采用显微硬度计和电化学工作站测试其硬度和腐蚀行为。研究表明,按照直流、单脉冲和双脉冲电沉积方式,复合镀层的致密性和显微硬度依次增加,孔隙率、镀速和晶粒尺寸依次减小。脉冲沉积复合镀层中TiC含量明显少于直流电沉积镀层中的TiC含量。双脉冲电沉积复合镀层的显微硬度为 HV 740.5,比直流电沉积镀层高67%。与直流和单脉冲沉积镀层相比,双脉冲电沉积复合镀层在3.5wt%NaCl 溶液中的自腐蚀电流密度降低了一个数量级(5.275×10−6 A·cm−2),自腐蚀电位明显正移(−0.113 V),电荷转移电阻为最大,表现出最好的耐蚀性。

     

    Abstract: To improve the quality of electrodeposited Ni-nano TiC composite coating, the Ni-nano TiC composite coating was prepared on the Q235 steel by electrodeposition. The effects of three different electrodeposition methods of direct current (DC), single pulse and double pulse on the microstructure and surface properties of the composite coating were compared and analyzed. The surface morphology and element distribution of the coatings were analyzed by SEM/EDS. The phase and grain size of the coatings were studied by XRD, and the hardness and corrosion behavior were tested by microhardness tester and electrochemical workstation respectively. The results show that the compactness and microhardness of the composite coating increase in turn, and the porosity, plating rate and grain size decrease in turn according to DC, single pulse and double pulse electrodeposition methods. The content of TiC in pulse deposition composite coating is obviously less than that in DC deposition coating. The microhardness of double pulse electrodeposition composite coating is HV 740.5, which is 67% higher than that of DC electrodeposition coating. Compared with DC and single pulse electrodeposited coatings, the self-corrosion current density of double pulse electrodeposited composite coatings in 3.5wt%NaCl solution decreases by an order of magnitude (5.275×10−6 A·cm−2), the self-corrosion potential shifts positively (−0.113 V), and the charge transfer resistance is the largest, showing the best corrosion resistance.

     

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