摘要
目的改善Ti6Al4V合金的耐磨和耐蚀性能,探究辅助渗氮手段的引入对Ti6Al4V合金离子渗氮组织和性能的影响。方法利用空心阴极放电(Hollow Cathode Discharge,HCD)及稀土氧化物(Y_(2)O_(3)纳米颗粒)辅助在720℃对Ti6Al4V合金进行4 h离子渗氮处理。通过光学显微镜、扫描电子显微镜、X射线衍射仪、显微硬度测试仪、往复式摩擦磨损实验仪以及电化学工作站,对比研究常规离子渗氮、HCD辅助离子渗氮以及HCD复合稀土氧化物辅助离子渗氮3种条件下Ti6Al4V合金的渗氮组织和性能。结果HCD复合稀土氧化物辅助离子渗氮条件下,Ti6Al4V合金表面生成约126μm厚的渗氮层,分别是常规离子渗氮条件和HCD辅助离子渗氮条件的3.1、2.4倍。化合物层中,TiN含量显著增加,渗氮层表面硬度达到1067.9HV0.05。渗氮层整体硬度明显提高,且硬度梯度降低。Ti6Al4V合金的摩擦系数从常规离子渗氮时的0.4降至0.2。同时,TiN含量的提高,使Ti6Al4V合金在3.5%NaCl溶液中的自腐蚀电流降低,极化电阻增大,耐蚀性能得到改善。结论HCD复合Y_(2)O_(3)辅助可显著提高氮势,促进氮向Ti6Al4V合金内快速扩散,提高合金的硬度,改善合金的耐磨性能和耐蚀性能。
The work aims to improve the wear and corrosion resistance of Ti6Al4V alloy and explore the effect of auxiliary means used in plasma nitriding on the microstructure and properties of nitrided layer.Hollow cathode discharge(HCD)and rare earth(Y_(2)O_(3)nanoparticle)were introduced to assist the plasma nitriding of Ti6Al4V alloy at 720℃for 4 h.Three different sets of plasma nitriding conditions were selected,namely conventional plasma nitriding(PN),plasma nitriding with HCD(PN with HCD)and plasma nitriding with HCD and Y_(2)O_(3)(PN with HCD and Y_(2)O_(3)).The hardness,wear and corrosion properties of the alloy were tested by microhardness tester,reciprocal linear sliding tester and electrochemistry station.The microstructure and phase composition were analyzed by means of optical microscopy,scanning electron microscopy and X-ray diffraction.Under the condition of plasma nitriding with HCD and Y_(2)O_(3),the nitrided layer with a thickness of about 126μm was formed on the Ti6Al4V alloy surface,which was 3.1 and 2.4 times thicker than that obtained by conventional plasma nitriding and plasma nitriding with HCD respectively.The content of TiN in the compound layer increased significantly,resulting in an increase in the surface hardness of the nitriding layer to 1067.9HV0.05,which was 26.7%and 8.5%higher than those of the other two sets respectively.The overall hardness of the nitriding layer was obviously increased,but the hardness gradient was reduced.The friction coefficient of Ti6Al4V alloy decreased from 0.4 under the conventional plasma nitriding condition to 0.2,and the corrosion resistance of the alloy in 3.5wt.%NaCl solution was improved.HCD is a special glow discharge phenomenon that occurs mainly inside a cavity-like cathode and can produce high-density plasma.The use of appropriate HCD for plasma nitriding can increase the nitrogen potential and accelerate the nitriding process.When HCD is combined with Y_(2)O_(3),the catalytic effect of rare earth elements in plasma nitriding is introduced and can be superimposed with the catalytic effect of HCD.As a rare earth element,yttrium has a special electronic structure and high activity.The yttrium atom can combine with the active nitrogen atoms in the plasma to generate rare earth nitride that promotes the adsorption of nitrogen on the alloy surface and the penetration of nitrogen into the alloy.At the same time,the large atomic radius of yttrium atom leads to the lattice distortion and accelerates the diffusion of nitrogen inside the alloy.In this study,Y_(2)O_(3)particles are used as the rare earth source.The yttrium elements(atoms or ions)can be released by the bombardment of high-energy particles generated by HCD.In the high-density plasma region of the hollow cathode,the interaction between yttrium elements and active nitrogen atoms is easier,and the catalytic effect of rare earth is enhanced.It is known from the above results that the combination of HCD with Y_(2)O_(3)is an effective method to substantially increase the nitrogen potential and promote the diffusion of nitrogen into the Ti6Al4V alloy during the plasma nitriding.In this case,the wear and corrosion resistance of the Ti6Al4V alloy can be improved.
作者
陈赛男
董志宏
鲍泽斌
CHEN Sainan;DONG Zhihong;BAO Zebin(Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China;School of Materials Science and Engineering,University of Science and Technology of China,Hefei 230026,China)
出处
《表面技术》
EI
CAS
CSCD
北大核心
2024年第5期78-84,107,共8页
Surface Technology
基金
中国科学院重点部署项目(ZDRW-CN-2021-2-2)。
