表面氧化及离子注氮对NiTi形状记忆合金耐腐蚀性能的影响

Effect of surface oxidation and nitrogen ion implantation on corrosion resistance of equiatomic NiTi shape memory alloy

采用电化学测试的方法,研究了表面氧化以及表面氧化 离子注氮两种表面改性方式对NiTi形状记忆合金在人体生理模拟液(Hank′s溶液)中腐蚀行为的影响。腐蚀电位和极化曲线的测量结果表明表面氧化 离子注氮的方法使NiTi合金材料的腐蚀电位正移,维钝电流密度下降,钝化电位区间扩大,合金表面耐蚀性明显提高。尤其是NiTi合金在进行氮离子注入后,测得击穿电位显著上升,增强了表面膜的抗局部腐蚀能力,因而表面氧化 离子注氮的改性方法可使材料的耐蚀性达到最佳。通过XPS的分析发现,离子注氮后合金表面形成氮化钛相以及富含羟基的化学效应,使NiTi基体的电化学性能得到提高。

The key to the biocompatibility of NiTi implants resides in the improvement of the material's corrosion resistance. To protect the surface of NiTi from corrosion, an ion implantation method was proposed. In the present work, surface oxidized sample was implanted with nitrogen at an energy of 100 keV. The corrosion resistance properties was examined by the anodic polarization methods in a simulated body fluid (SBF) at a temperature of 37°C and contrasted to non-implanted NiTi samples. The composition and structure of the implanted layers were investigated by SEM, ED AX and XPS. The results from the electrochemical measurements provide evidence that nitrogen ion implantation increase the corrosion resistance of NiTi shape memory alloy.