Laser-based directed energy deposition (DED) technique has the potential for precise restoration of localized damage in high value components. This paper describes the indigenous development and sub-systems integration of a robotic restoration system based on laser DED. This system comprises of four modules: a robot for imparting desired outcome; 3 kW fiber laser as the energy source; powder feeder; and a quartz block head connected deposition head with co-axial powder delivery nozzle. In addition, a damage detection technique using a laser line scanner has been developed. Experimental characterization of the developed system is also presented. Laser DED involves a complex interplay of several physical phenomena, such as powder particle injection, melt pools formation, deposition spreading, and coupled metallo-thermomechanical behavior which induces residual stresses in the deposition and the substrate. In order to understand the complete process, each of these vital mechanisms needs to be studied. Computational fluid dynamics models have been developed to predict the flow and injection of powder particles via coaxial annular nozzle, melt pool spreading and deposition geometry. The major challenge in restoration via DED is the compromised service life of the restored part due to unfavorable residual stresses originating from differential thermal expansion/contraction, volume dilation and transformation plasticity. A fully coupled metallo-thermomechanical model has been presented in this paper. The residual stresses obtained from the model have been validated using residual stress measurements from X-ray diffraction and neutron diffraction techniques. Finally, process maps have been developed based on these physics-based models to obtain optimal process parameters to ensure favorable residual stresses, dilution and geometry in DED.

基于激光的定向能量沉积（DED）技术具有精确恢复高价值组件中局部损坏的潜力。本文介绍了基于激光DED的机器人修复系统的本地开发和子系统集成。该系统包括四个模块：一个用于传递期望结果的机器人；3 kW光纤激光器作为能源；送粉器 石英块头连接沉积头和同轴粉末输送喷嘴。另外，已经开发了使用激光线扫描仪的损伤检测技术。还介绍了开发系统的实验特性。激光DED涉及多种物理现象的复杂相互作用，例如粉末颗粒注入，熔池形成，沉积扩散，以及耦合的金属热力学行为，会在沉积物和衬底中引起残余应力。为了了解完整的过程，需要研究这些重要机制中的每一个。已经开发了计算流体动力学模型来预测粉末颗粒通过同轴环形喷嘴，熔池扩散和沉积几何形状的流动和注入。通过DED进行修复的主要挑战是由于差的热膨胀/收缩，体积膨胀和相变可塑性产生的残余应力不利，导致修复零件的使用寿命受损。本文提出了一种完全耦合的金属热力学模型。使用X射线衍射和中子衍射技术的残余应力测量值已经验证了从模型获得的残余应力。最后，基于这些基于物理的模型开发了工艺图，以获得最佳工艺参数，以确保DED中有利的残余应力，稀释和几何形状。