铸铁件的镍-磷合金化学镀工艺及性能研究

Studies on technologies and properties of electroless Ni-P plating on cast iron

对铸铁件进行镍-磷化学镀以提高其耐蚀性能。对镀层的成分分布、表面形貌、镀层硬度及硬度随回火温度的变化、镀层与基体的结合强度及镀层的耐蚀性进行了研究。结果表明:镀层磷含量为6%～8%,属中磷镀层;镀后,试样表面硬度得到大的提高,热处理可进一步提高表面硬度。镀层均匀、致密、孔隙率低且与基体结合牢固;划痕试验中当施加的法向力超过60N时,涂层与基体间才有裂纹产生:电化学极化试验结果表明,化学镀后,铸铁的抗腐蚀能力获得很大的提高,腐蚀率从6.337E-2mm/a减少到1.914E-2mm/a。

Technology of electroless Ni-P plating on cast iron was used for improving its corrosion resistance property. The properties of coatings,as distribution of elements, surface morphology, micro-hardness of the coatings, adhesion strength of the coating with the substrate, and corrosion resistance of the coating,were investigated. Results show that a middling phosphorus coating with 6%-8% P was obtained. After plating, the surface hardness of sample increases a lot, and the hardness will increase much more through tempering. A compact, even, low porosity and firm coating is formed on surface of cast iron by the technology introduced. Before vertical force of the diamond pyramid reaches 60 N, no crack between the coating and the substrate is observed. Results of potentiodynamic polarization experiments show that corrosion resistance of cast iron obtaines a large improvement after electroless Ni-P plating, corrosion rate decreases to 1.914E-2 mm/year correspondingly from 6.337E-2 mm/year of cast iron.