(Tb,Dy)Fe2合金表面离子注入渗氮改性及抗腐蚀性能研究

Surface Modification of(Tb,Dy) Fe_2 Alloy by Nitrogen Ion Implantation

采用离子注入技术在(Tb,Dy)Fe2稀土超磁致伸缩材料表面引入氮离子进行改性处理,研究了加速电压对材料表面相结构、微观形貌、表面硬度、抗酸碱腐蚀性能及磁致伸缩性能的影响。结果表明:离子注入渗氮后,(Tb,Dy)Fe2合金表面的REFe2相分解,生成了REN,α-Fe和Fe8N新相,材料表面微观形貌发生了明显变化,表面硬度明显提高。通过测试极化曲线研究了渗氮前后(Tb,Dy)Fe2合金在不同pH值NaCl溶液中的抗酸碱腐蚀性能,发现pH值相同条件下渗氮处理后(Tb,Dy)Fe2合金的自腐蚀电位Ecorr较渗氮前明显正移且有钝化现象发生。在加速电压140 kV,离子注入剂量5.0×1017ion.cm-2条件下渗氮处理的(Tb,Dy)Fe2合金,处于20℃,3.5%NaCl溶液环境中,pH=4时,△Ecorr=0.23413 V;pH=7时,△Ecorr=0.18992 V;pH=10时,△Ecorr=0.01268 V,渗氮处理后(Tb,Dy)Fe2合金的抗酸腐蚀性能明显增强,抗碱腐蚀性能变化不明显。随着pH值的增大,渗氮与未渗氮(Tb,Dy)Fe2合金的抗腐蚀性能均变差。由于离子注入表面渗氮的渗氮层很薄,渗氮温度很低,渗氮处理没有破坏材料的内部基体结构,因此渗氮后材料渗氮处理没有破坏材料的内部基体结构,其磁致伸缩性能几乎未受影响。研究表明离子注入渗氮是(Tb,Dy)Fe2磁致伸缩材料表面改性的一种有效方法。

Effects of nitriding modification on surface phase structure,morphology,case hardness,corrosion resistance and magnetostriction of（Tb,Dy）Fe2 alloy were investigated by nitrogen ion implantation.The results showed that the surface REFe2 phase decomposed and transformed into REN,α-Fe and Fe8N phases after nitrogen ion implantation.The surface morphology of the alloy had an obvious change,and the case hardness was also greatly improved.The corrosion resistance properties of（Tb,Dy）Fe2 alloy were researched by tested polarization curves in NaCl solutions with different pH value.It was found that the nitrided alloy had higher corrosion potential Ecorr than non-nitrided ones in the same environment,and there were some passivations in their polarization curves.The corrosion resistance properties of the alloy before and after nitrided were tested in different pH value solutions（20 ℃,3.5%NaCl）,and the nitriding technological condition was 5.0×1017 ion · cm-2 and 140 kV.The results were as follows,pH=4,△Ecorr=0.23413 V;pH=7,△Ecorr=0.18992 V;pH=10,△Ecorr=0.01268 V.The results indicated that the corrosion resistance of nitrided alloy in acidic environment was better than non-nitrided ones,but it had no significant increase in strong alkaline environment comparatively.Furthermore,the corrosion resistance properties of the alloy before and after nitrided all became worse with the increase of the pH value.In addition,the magnetostriction performance of the alloy was almost not affected by ion implantation because of the nitrided layer was quite thin and the operating temperature was very low.The results proved that nitrogen ion implantation was an effective method for surface modification of（Tb,Dy）Fe2 alloy.