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

航空发动机在极其艰苦的条件下运行，许多部件受到损坏和/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）的组件至关重要。或者两者都被修复并恢复使用，从而达到它们的全部预期使用寿命，如果没有超过的话，在安全的情况下这样做。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吹制粉末定向能量沉积（LBP-DED）。在LBP-DED工艺期间，激光用于在目标修复位置处创建熔池，然后使用喷嘴将惰性气体携带的恒定粉末流聚焦在所创建的熔池上。当激光移动时，熔池在激光后面固化，并形成修复层。然后，建立连续的修复层以产生最终的存款。最终的存款通常随后被进一步处理，例如热处理、机加工、抛光，以满足修复所需的最终条件。使用曼彻斯特在以前的增材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SEM/TEM），详细的微观结构表征和对材料添加（MA）沉积物内缺陷形成的理解，以及这些缺陷与输入粉末的关系，需要特定钛和镍合金的工艺参数和机械性能。冶金分析和所获得的理解将支持一个关键的修复策略，正在全球范围内开发的所有燃气涡轮机发动机，其中该技术可以利用。

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.