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

涡轮发动机中的材料暴露在恶劣的使用环境中，导致其完整性和性能降低。为了提高发动机的效率，减少NOx/CO2的排放，涡轮发动机的温度将会提高。目前涡轮叶片材料已接近熔化温度，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发动机最热部件的镍基高温合金。虽然这些材料具有良好的机械性能，但抗氧化性较差，这限制了它们的应用。提高抗氧化性是这个项目要解决的挑战。这个问题是利用硼的独特性质来解决的。硼是玻璃形成的元素之一。当添加到Nb-Si合金中时，可以在合金氧化时在表面形成一层玻璃状的自愈层，从而提高抗氧化性。本项目通过材料表征、恒温氧化和循环氧化试验，研究了硼对Nb-Si基合金性能的影响。该项目旨在确定氧化机制、引入硼的影响及其与常用添加剂如Al、Sn、Ge等的协同作用。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更好的抗氧化性和自我修复能力的合金，这将大大节省使用成本。一旦建立起来，这一知识可能会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.