A closed-loop laser additive manufacturing (CLAM) system was developed to monitor and control layer-by-layer fabrication via directed energy deposition (DED). The well-modified laser additive manufacturing (LAM) package utilizes a thermal infrared camera and thermal image processing algorithms to extract and control the thermal dynamics of the process, including (i) cooling rate, (ii) melt pool temperature, and (iii) heating rate. Martensitic stainless steel of grade S410-L was used to cumulatively deposit 5 layers on top of each other at different processing conditions without closed-loop control. Significant deviations of cooling rate and melt pool temperature are observed within different layers of a thin-wall structure without feedback control in the open-loop state. To assess the effects of cooling rate control on final LAM properties, three samples with different setpoint cooling rates of 550, 1100, and 1750 °C/s are tested under closed-loop conditions. Microstructural and microhardness maps and profiles of open-loop and closed-loop samples reveal highly uniform and controlled hardness profiles when closed-loop control is applied, in contrast to highly varying properties in samples produce in open-loop operation. The current research results illustrate how one can achieve controlled microstructural characteristics and mechanical properties through real-time control of the cooling rate during the LAM process.

开发了闭环激光增材制造（CLAM）系统，以通过定向能量沉积（DED）监视和控制逐层制造。经过改进的激光增材制造（LAM）软件包利用红外热像仪和热图像处理算法来提取和控制过程的热动力学，包括（i）冷却速度，（ii）熔池温度和（iii））加热速率。在没有闭环控制的情况下，使用S410-L级的马氏体不锈钢在彼此不同的加工条件下在彼此之上累计沉积了五层。在开环状态下没有反馈控制的情况下，在薄壁结构的不同层中观察到冷却速率和熔池温度的显着偏差。为了评估冷却速率控制对最终LAM性能的影响，在闭环条件下测试了三个设定温度分别为550、1100和1750°C / s的样品。开环和闭环样品的显微结构和显微硬度图以及轮廓在采用闭环控制时显示出高度均匀且受控的硬度曲线，与开环操作中产生的样品的高度变化特性相反。