The thermal history of the directed energy deposition process monitored by pyrometer and camera

Abstract

In the process of directed energy deposition (DED), the local thermal history of a component can change significantly owing to its complex heat transfer characteristics. The main objective of this study is to elucidate the distribution of the thermal history of a static scroll plate by monitoring its manufacturing process through a pyrometer and camera and to provide insights into the factors affecting the variation of its thermal history from the point of view of the part shape and scanning strategy. The melt pool area and temperature were extracted using a camera and pyrometer as the thermal features under study, and the thermal features were mapped in three dimensions. This mapping strategy provides a comprehensive visualization of the distribution of thermal features in parts with equal and variable cross-section structures. In the case of an equal cross-section structure, three factors, printing time, scan vector length, and probability density, are selected to analyze the main factors affecting the distribution of thermal features. In the case of the variable cross-section structure, the effects of the layer printing time, cumulative layer printing time, and probability density on the distribution of thermal features were analyzed. By calculating the correlation between the thermal features of the monitored signals and the factors mentioned above, it was found that the factors affecting the thermal distribution of the parts vary in different structures. In equal cross-section structures, the probability density plays a pivotal role, while in variable cross-section structures, the cumulative layer printing time has the most significant influence on the thermal distribution. The above studies have provided a better understanding of the thermal processes of DED technology, paving the way for the control and optimization of DED manufacturing.