In-situ powder mixing for laser-based directed energy deposition of functionally graded materials

The mixing of powders is a highly relevant field under additive manufacturing, however, it has attracted limited interest to date. The in-situ mixing of various powders remains a significant challenge. This paper proposes a new method utilizing a static mixer for the in-situ mixing of multiple powders through the laser-based directed energy deposition (DED) of functionally graded materials. Firstly, a powder-mixing experimental platform was established; WC and 316L powders were selected for the mixing experiments. Secondly, scanning electron microscopy, energy dispersive spectroscopy, and image processing were used to visually evaluate the homogeneity and proportion of the in-situ mixed powder. Furthermore, powder-mixing simulations were conducted to determine the powder-mixing mechanism. In the simulations, a powder carrier gas flow field and particle mixing were employed. Finally, a WC/316L metal matrix composite sample was produced using laser-based DED to verify the application potential of the static mixer. It was found that the static mixer could adjust the powder ratio online, and a response time of 1-2 s should be considered when adjusting the ratio of the mixed powder. A feasible approach for in-situ powder mixing for laser-based DED was demonstrated and investigated, creating the basis for functionally graded materials.