In this study, the suitability of a magnetron sputtered Al–18Si (at.%) coating as oxidation protection for a γ-TiAl based TNB-V2 alloy was investigated. The coating microstructure and its changes as well as the evolution of the different phases during the different steps, deposition process, post heat treatment and isothermal oxidation test, was studied using x-ray diffraction as well as scanning and transmission electron microscopy.

The well adherent coating provides a homogenous, dense and crack free crystalline microstructure of Si grains in an Al matrix. The phase evolution analysis during a 20 h post-heat treatment at 550 °C with in situ x-ray diffraction reveals the complete formation of the TiAl₃ phase due to the reaction of Ti from the TNB-V2 substrate and Al from the coating. During oxidation at 850 °C for 300 h, a thermally grown α-Al₂O₃ layer was formed providing excellent oxidation resistance. The formation of α-Al₂O₃ relies on the presence of TiAl₃ whereas the silicon acted as a getter for Ti and thus could prevent the formation of TiO₂. Furthermore, the finally formed Ti₅Si₃ phase reduces the inwards diffusion of Al into the substrate and prevents fast Al depletion in the coating. Moreover, the hierarchical coating microstructure, consisting of a TiAl₃ matrix with a network-like structure of the Ti₅Si₃ phase, could be beneficial in terms of mechanical properties.

在这项研究中，研究了磁控溅射Al-18Si（at。％）涂层作为基于γ-TiAl的TNB-V2合金的氧化防护的适用性。使用X射线衍射以及扫描和透射电子显微镜研究了涂层的微观结构及其变化，以及在不同步骤，沉积过程，后热处理和等温氧化试验中不同相的演变。

良好粘附的涂层在Al基体中提供了Si晶粒的均匀，致密且无裂纹的晶体微观结构。在550°C的条件下进行20 h热处理后的相演化分析（原位X射线衍射）表明，由于TNB-V2基材中的Ti和涂层中的Al的反应，TiAl ₃相的完整形成。期间，在850℃下300h时的氧化，热生长的α-Al ₂ ö ₃形成层提供优异的耐氧化性。形成的α-Al ₂ ö ₃依赖的TiAl的存在₃而充当对钛吸气剂的硅，因此可以防止二氧化钛的形成₂。此外，最终形成的Ti ₅ Si ₃相减少了Al向基材中的向内扩散，并防止了涂层中Al的快速耗尽。此外，由TiAl ₃基体和Ti ₅ Si ₃相的网状结构组成的分层涂层微观结构在机械性能方面可能是有益的。