Prediction of deposit characteristics based on the discrete coaxial nozzle during laser direct metal deposition

The variation in powder mass concentration distribution caused by the nozzle structure influence the deposit profiles and quality to a considerable extent in laser direct metal deposition (DMD) process. For symmetrical discrete nozzles, the powder mass concentration distribution was described, and the results were utilized in a molten pool model without powder feeding simulations. The evolution of the molten pool dimensions, and the temperature and velocity fields of single-track deposit were explored. The influences of specific energy (E) and mass per unit length (MUL) on the characteristics of single-track deposits were investigated. The correlation between the powder stream position and the concentration distribution was clearly expressed. The results indicated that the width/height ratio of single-track deposits decreased significantly, and the contact angle first increased and then decreased with higher specific energy intensity. Besides, the variation in the spatial position of the powder stream led to different mass concentration distributions, resulting in the tilt of deposit cross-sections towards the side with a higher mass concentration. The model exhibited a capacity for predicting the profiles of the deposits formed by symmetrical discrete nozzles.