Self-healing ability of Nb-Si based alloys with boron for improved environmental performance

涡轮机发动机中的材料暴露于恶劣的使用环境中，导致其完整性和性能降低。为了提高发动机的效率并减少NOx/CO2的排放，将提高涡轮机发动机温度。目前的涡轮机叶片材料接近熔化温度，因此需要新的耐火材料。目前正在研究Nb-Si基合金以取代用于涡轮机发动机最热部件的Ni基高温合金。虽然这些材料具有良好的机械性能，但抗氧化性可能较差，这限制了它们的应用。提高抗氧化性是本项目要解决的挑战。这个问题将利用硼的独特性质来解决。硼是玻璃形成元素之一。当添加到Nb-Si合金中时，在合金氧化时可在表面上形成玻璃状自修复层，从而改善抗氧化性。本计画借由材料特性分析、等温及循环氧化实验，研究硼对铌矽基合金性质之影响。该项目旨在确定氧化机制，硼引入的影响及其与常用添加剂的协同作用，如铝，锡，锗等实验结果将与计算模型进行比较。这项工作将导致发现具有改进的抗氧化性和自修复能力的合金，这可以节省大量的使用成本。一旦建立，这种知识可以扩展到其他合金系统。

Materials in turbine engines are exposed to harsh in-service environments, resulting in the reduction in their integrity and performance. To improve efficiency of engines and to decrease emissions of NOx/CO2, turbine engine temperatures will be increased. Current turbine blade materials are approaching melting temperatures; hence new refractory materials are needed.Nb-Si based alloys are currently investigated to replace Ni-based superalloys used in the hottest part of a turbine engine. Although these materials have good mechanical properties, the oxidation resistance can be poor, which limits their application. Improving the oxidation resistance is the challenge to be addressed in this project.The issue is to be tackled utilising the unique nature of boron. Boron is one of the glass-forming elements. When added to Nb-Si alloys, a glassy self-healing layer may form on the surface upon oxidation of the alloy, improving oxidation resistance. The project investigates the effect of introducing boron on the properties of Nb-Si based alloys through materials characterisation and isothermal and cyclical oxidation tests. The project aims to determine the oxidation mechanism, the impacts of boron introduction and its synergy with commonly used additions e.g. Al, Sn, Ge etc. The experimental outcomes will be compared with computational models. This work will lead to the discovery of alloys with improved oxidation resistance and self-healing ability, which could save significant in-service costs. Once established, this knowledge may be extended to other alloy systems.