X-ray Computer Tomography and Microstructural Characterisation of Additive Structures for Advanced Repair of Aeroengine Components

航空发动机是在极其恶劣的条件下运行的，许多部件都会受到损坏和/或磨损。从可持续性和成本的角度来看，高价值、资源密集型(含稀土等)的部件至关重要。或两者都修复并恢复使用，以便达到其完全预期的使用寿命，如果没有超过安全的话。正在开发的一种用于修复高价值、高完整性部件的技术是激光喷粉定向能量沉积(LBP-DED)。在LBP-DED过程中，使用激光在目标修复位置产生熔池，然后使用瞄准所产生的熔池的喷嘴聚焦由惰性气体携带的持续的粉末流。当激光移动时，熔池在激光后面凝固，并形成修复层。然后连续的修理层被建立起来，以产生最终的沉积物。最后的沉积物通常经过进一步处理，如热处理、机械加工和抛光，以满足维修所需的最终条件。利用曼彻斯特在以前的添加剂层结构研究中已经使用的微观结构评估方法和专业知识(包括X射线计算机断层扫描技术、EBSD和扫描电子显微镜/电子显微镜)，需要详细的微观结构表征和了解材料添加(MA)沉积中缺陷的形成，以及这些缺陷与特定钛和镍合金的输入粉末、工艺参数和机械性能的关系。冶金分析和获得的理解将支持全球正在为所有可以利用这项技术的燃气轮机发动机制定的关键维修战略。

Aero engines are operated under incredibly arduous conditions, with many components suffering from damage and/or wear. From a sustainability and cost perspective, it is essential that components which are either high value, resource intensive (contain rare earths etc.) or both, are repaired and returned to service so that their full expected service life is reached, if not exceeded where safe to do so. One technology that is being developed for the repair of high value, high integrity components is laser blown powder directed energy deposition (LBP-DED).During the LBP-DED process a laser is used to create a melt pool at the targeted repair location, a constant stream of powder, carried by inert gas, is then focused using a nozzle targeted at the melt pool created. As the laser moves the melt pool solidifies behind the laser and a repaired layer is created. Successive layers of repair are then built up to produce the final deposit. The final deposit is usually then further processed e.g. heat treated, machined, polished to meet the final condition required of the repair. Using the microstructural assessment methodology and expertise already used at Manchester in previous studies of additive layer structures (including X-ray computer tomography techniques, EBSD and SEM/TEM), a detailed microstructural characterisation and understanding of the formation of defects within Material Addition (MA) deposits, and the relationship these defects have to the input powder, process parameters and mechanical properties of specific titanium and nickel alloys is required. Metallurgical analysis and the understanding obtained will support a key repair strategy that is being developed globally for all gas turbine engines in which this technology can be exploited.