镍基高温合金中S元素对基体与热障涂层界面稳定性的影响

Effect of Element S on Interfacial Stability of Matrix and Thermal Barrier Coating in Nickle-Based Superalloys

镍基高温合金中的S元素会对合金性能产生负面影响,在服役过程中含S体系的界面处会发生氧化膜剥落等现象,进而导致合金发生失效。本工作利用第一性原理计算,围绕S元素在镍基高温合金及其涂层的偏聚现象,研究了S元素对合金及NiAl涂层的影响机制。分析了Ni_(3)Al/NiAl、NiAl/Al_(2)O_(3)的纯净界面和含S元素界面2种模型的界面黏附功、偏聚能及界面电荷情况。结果表明,合金中含S元素的体系界面黏附功变小,进而降低了界面稳定性;S元素在各自的体系内均有向界面偏聚的倾向。通过分析其界面电子结构(如二次差分电荷密度、Bader电荷、局域电子密度、态密度等)的演变,发现S元素的存在会减弱界面附近的键合,进而降低局部连接的紧密性。最后揭示了S元素对体系界面稳定性的影响机制。

The existence of elemental S in nickle-based superalloys negatively impacts their performance.The oxide film at the interface of the nickle-based superalloy peels off during the service process,leading to the failure of the alloy.However,the influence mechanism of the elemental S on the interface of the matrix and the coating layer is yet to be studied.Herein,the influence mechanism of the elemental S on the nickle-based superalloy and NiAl coating was studied using the first-principle calculation,especially focusing on the S segregation phenomenon.The interface adhesion work,segregation energy,and interface charge of the pure and S-doped interfaces of Ni_(3)Al/NiAl and NiAl/Al_(2)O_(3)were analyzed.The calculated results show that the interfacial adhesion work of the system decreases when the elemental S is present,resulting in reduced interface stability;in these systems,the elemental S tends to segregate toward the interface.By analyzing various aspects of the interface electronic structures(such as differential charge density,Bader charge,electron localization function,and densities of states),it was found that the bonding near the interface was weakened in the system with the elemental S,thereby reducing the tightness of the local connection.The influence mechanism of the elemental S on the interfacial stability of the system was finally revealed.