Investigation of process characteristics of quasi-continuous-wave laser-based directed energy deposition.

• The process characteristics of quasi-continuous-wave laser-based directed energy deposition is studied. • Laser mode-related formation mechanism of powder adhesion is revealed. • Critical factors of the deposition point formation are confirmed. • Surface quality is improved by the process adjustment strategy. Directed energy deposition (DED) is an advanced additive manufacturing technique that has garnered considerable success in various industrial sectors. However, the conventional continuous-wave laser mode employed in DED often results in excessive heat buildup and coarse microstructure, leading to compromised performance. The utilization of quasi-continuous-wave laser-based DED (QCW-DED) has emerged as a promising solution to these challenges. Nevertheless, limited understanding of the process characteristics associated with QCW-DED has impeded further exploration of thermal and microstructural control. Therefore, this study aims to comprehensively evaluate QCW-DED process characteristics, including deposition point morphology and surface quality, through a combination of experimental measurements and simulation analysis. The findings indicate that the height of the deposition point is primarily governed by heat and mass transfer, while the diameter is predominantly influenced by heat transfer. Consequently, optimizing process parameters based solely on laser input energy calculations is inadequate for QCW-DED. Furthermore, the phenomenon of powder adhesion was observed to accumulate more prominently at the periphery of the deposition point rather than in its central region. As a result, suggesting higher laser power and shorter laser exposure time is recommended to enhance the quality of the deposition point and mitigate powder adhesion issues. [ABSTRACT FROM AUTHOR]