Numerical study of powder flow characteristics of coaxial nozzle direct energy deposition at different operating and design conditions

This study investigates key parameters impacting powder particle efficiency in coaxial nozzle systems crucial for direct energy deposition (DED) additive manufacturing. Utilizing simulations and experiments, it examines operational and design factors like stand-off distance, focus spot size, gas and powder flow rates, and powder distribution. Results identify an optimal stand-off distance (5–25 mm) yielding peak efficiencies of 42.43% and 39% for 10 g/min and 20 g/min powder flow rates, respectively. Increased focus spot size (1–3 mm) correlates positively with efficiency, peaking at 53.03% with a 3 mm spot. Powder mass flow rate and efficiency show complex relationships within the 5–25 g/min range. Nozzle design significantly influences particle efficiency in DED, emphasizing control and optimization of operational parameters. Strategies include stand-off distance optimization, specific focus spot size adjustment, and consistent powder distribution for efficiency enhancement. Flow dynamics analysis reveals smaller powder particles exhibit higher efficiency due to reduced flow separation angles. Numerical simulations align closely with experiments, indicating varying optimum stand-off distances for different powder flow rates. In conclusion, this study aims to enhance powder particle efficiency (η) under diverse operational conditions, providing insights applicable to industries using DED in manufacturing.