Integral numerical modeling of the deposition profile of a cold spraying process as an additive manufacturing technology

Cold spraying is a potential alternative process to the current melting-based strategies of additive manufacturing technology that is expected to improve the mechanical properties significantly. However, the process, applied traditionally for coating rather than fabrication, lacks a method to ensure the manufacturing precision. The deposition profile, the key to this issue, is determined by the properties of the powder jet produced by the nozzle. Although significant efforts have been made to reduce the jet size and experimentally observe the deposition profile, a systematic study is required to gain a deep insight into the mechanism of the deposition profile and thus provide a solid base to optimize the process parameters. To address this issue, in this paper, a method is proposed to characterize the deposition profile quantitatively, and an integral analysis framework is established to connect all the procedures in the process, including gas flow, particle flight, particle impact, and particle deposition. In particular, a rule-based deposition model was developed using the impact physics as the foundation and the powder jet as the input. The structure of the powder jet, obtained from CFD analysis, was studied in detail to reveal the key factors and their distributions. In addition to aerodynamic drags, collision and reflection restrictions by the nozzle wall were found to largely contribute to the forming of the powder jet. The deposition profile obtained in the typical condition was characterized quantitatively, and the possible reason behind the inferior manufacturing precisions was uncovered. Moreover, the overlapping deposition was studied, revealing that adjacent depositions were uncoupled in the sense of dimensional profile. The influence of the injection size on the deposition profile was investigated and it was found that it is difficult to achieve both the manufacturing resolution and precision by adjusting this particular process parameter.