硬质合金表面化学镀镍工艺的研究

Research on the Technology of Electroless Nickel Plating on Cemented Carbide Surface

本文以硫酸镍(Ni SO4·6H2O)为主盐、次亚磷酸钠(Na H2PO2·H2O)为还原剂,通过改变络合剂的种类与含量对硬质合金表面进行化学镀镍。用扫描电镜及能谱、X射线衍射仪、涂层附着力自动划痕仪和电化学测试系统分析表征硬质合金镀镍前后的形貌、成分、相组成、结合力以及耐蚀性。结果表明,在p H=8,T=80℃的施镀条件下,镀层为非晶结构且耐蚀性较镀前有一定的提高,镀层表面主要含有Ni元素和P元素,其中Ni元素占了很大的比例,镀层物相组成为Ni P2和Ni,且膜基结合力在100 MPa以上,镀层厚度受络合剂的影响较大。镀液成分为Ni SO4·6H2O∶25 g/L、Na H2PO2·H2O∶30 g/L、柠檬酸钠(Na3C6H5O7·2H2O)∶45 g/L、氯化铵(NH4Cl)∶30 g/L、硫脲(H2NCSNH2)∶1 mg/L时得到的镀层性能最佳。

In this paper, the technology of electroless nickel plating on cemented carbide surface was studied by using nickel sulfate main salt and sodium hypophosphite as reducing agent, and by changing the kinds and contents of complexing agent. The composition, morphology, coating adhesion and the corrosion resistance of cemented carbide before and after electroless nickel plating were analysized by SEM, XRD and coating adhesion automatic scratch tester as well as electrochemical testing system. The results show that, under the plating condition of p H=8 and T=80 ℃, the coating is of amorphous structure and the corrosion resistance is improved. The coating surface mainly contains Ni and P elements, and the Ni element accounts for a large proportion. The phase composition of the coating is Ni P2 and Ni, and the binding force between the coating and the substrate is above 100 MPa. The coating thickness is greatly influenced by the complexing agent. The coating obtains the best performance with the plating solution composition of sulfate nickel [NiSO4according to6H2O]（25 g/L）, sodium hypophosphite [Na H2PO2 according to 2H2O]（30 g/L）, citric acid, sodium [Na3C6H5O7according to2H2O]（45 g/L）, ammonium chloride [NH4Cl]（30 g/L） and thiourea [H2NCSH2]（1 mg/L）.