基于EET理论的离子氮化层性能研究

Study on Properties of Ionic Nitriding Layer Based on EET Theory

目的分析离子渗氮层中Fe-N金属间化合物的价电子结构与渗层性能之间的关系。方法以45号钢为研究对象,测试45号钢离子渗氮后的硬度、渗层厚度、物相组成、摩擦磨损性能、耐蚀性和力学性能。根据XRD测试结果,应用EET理论,对渗层中的Fe-N金属间化合物相的价电子结构、键能、结合能等进行计算,并分析性能与Fe-N金属间化合物价电子结构之间的关系。结果渗氮温度为520℃、氮氢流量比为3∶1时,渗层的硬度以及耐磨、耐蚀性均最高,但渗层的脆性最高,其冲击吸收功下降至母材的26%。计算结果表明,α-Fe、Fe_(4)N、Fe_(3)N和Fe_(2)N的共价电子密度计算值分别为299.13、367.68、416.45、458.78 nm^(-3),晶体的平均键合能分别为412.65、444.02、472.48、486.61 kJ/mol,晶格电子密度的计算值分别为133.36、108.58、84.72、81.74 nm^(-3),晶体的塑性因子分别为76.20、14.75、3.66、3.65。结论ε相对渗层的塑韧性影响最大,适当降低离子渗氮温度以及氮氢流量比,能够有效减少ε的含量,以改善渗氮件塑性差的问题。

This study aims to analyze the relationship between the valence electron structure of Fe-N intermetallic compounds in ionic nitriding layers and the performance of the layer.The 45 steel was used as the research object and the hardness,thickness of nitrided layer,phase composition,friction and wear properties,corrosion resistance,and mechanical properties were teseted after ion nitriding.Based on the XRD results and EET theory,the valence electron structure,bond energy and bond energy of Fe-N intermetallic compound phase in the infiltrated layer were calculated,and the relationship of properties and valence electron structure were anlysized.The experimental results show that when the nitriding temperature was 520℃ and the nitrogen hydrogen flow ratio was 3∶1,the hardness,wear resistance and corrosion resistance of the nitrided layer were highest,but the brittleness was also the highest,and the impact absorption energy was reduced to 26%of the base metal.The calculation results indicated that covalent electron density ofα-Fe,Fe_(4)N,Fe_(3)N and Fe_(2)N were 299.13,367.68,416.45,458.78 nm-3,crystal aerage bonding energies were 412.65,444.02,472.48,486.61 kJ/mol.Covalent electron density of α-Fe,Fe_(4)N,Fe_(3)N and Fe_(2)N were 133.36,108.58,84.72,81.74 nm^(-3),crystal plasticity factor were 76.20,14.75,3.66,3.65.Under the experimental conditions,theεhas the greatest influence on the plastic toughness of the nitrided layer,the content ofεphase could be effectively reduced by properly reducing the plasma nitriding temperature and nitrogen hydrogen flow ratio to improve the mechanical properties of nitriding parts.