Repair of Single Crystal Turbine Blades by the Laser Engineered Net Shaping Process

该研究项目的主要目标是了解如何通过激光局部熔化和再凝固来消除单晶中的缺陷，并随后将这些基本信息用于修复航空航天发动机和发电厂中使用的单晶涡轮叶片中的缺陷。导致单晶在重新凝固过程中缺陷消除的条件目前还不清楚，这阻碍了成功的修复。这项研究将采取跨学科的方法，让机械工程和材料工程系的学生和教职员工共同努力，首先确定如何在不同的凝固条件下保留单晶的性质。这一基础性研究将产生单晶凝固的物理模型和数值模型。这些基本信息将用于控制激光修复过程，以便熔化区域以消除缺陷的方式重新凝固，并恢复涡轮叶片的单晶性质。如果成功，这项研究的结果将提供对单晶凝固机理的更好理解，并导致建立目前尚不存在的单晶凝固的物理和数值模型。此外，将这些结果应用于单晶涡轮叶片的修复将导致与制造和更换涡轮叶片相关的大量成本节约。例如，一个涡轮叶片目前的制造成本约为3万美元，而一个发动机包含许多叶片。在某些情况下，叶片不能使用，因为在初始制造过程中形成了缺陷。一旦制造出无缺陷的叶片并投入使用，它最终必须因磨损而退出使用，并换成新的叶片。目前，大多数出现制造缺陷或使用损坏的叶片必须报废，因为没有可靠的技术来修复这些缺陷。该计划的工业合作伙伴已经确定，一种成功的维修方法可以在每次检查和/或大修发动机时节省多达10万美元。

The primary objectives of this research project are to understand how defects in single crystals can be eliminated by localized melting and re-solidification using lasers, and subsequently use this basic information for repairing defects in single crystal turbine blades that are used in aerospace engines and power plants. The conditions, which lead to defect elimination during re-solidification in single crystals, are currently not clearly understood, and this has precluded successful repair. The approach to be taken in this research is interdisciplinary and involves students and faculty in Mechanical Engineering and Materials Engineering Departments working together to first establish how the single-crystal nature can be preserved under different solidification conditions. This fundamental research will lead to a physical and numerical model of single crystal solidification. This basic information will then be applied to control laser repair processes so that the melted area re-solidifies in a manner that removes the defect and restores the single crystal nature of the turbine blade.If successful, the results of this research will provide an improved understanding of the mechanism of single crystal solidification and lead to the creation of physical and numerical models of single crystal solidification that are currently not available. In addition, application of these results for repair of single crystal turbine blades will lead to a substantial cost savings associated with manufacturing and replacement of turbine blades. For example, one turbine blade currently costs approximately $30,000 to manufacture, and one engine contains many blades. In some cases the blades cannot be used because of defects that formed during initial manufacturing. Once a defect-free blade is manufactured and placed into service, it must eventually be removed from service because of wear and replaced with a new blade. At present, most blades exhibiting manufacturing defects or service damage must be discarded because there is no reliable technique to repair these defects. The industrial partner of this program has determined that a successful repair method could result in savings of as much as $100,000 each time an engine is inspected and/or overhauled.