Powder jet variations using Low Pressure Cold Spraying – for an improvement of the spraying yield

Cold spraying appears as a promising way of additive manufacturing for developing new technological capabilities on massive materials as well as advanced functionalization of surfaces. Compared to high pressure cold spray, low pressure cold spray process takes advantage of numerous points like the low temperature (<600°C) and low pressure gas (<10 bars) using a compact device. Hence, wide range of applications can then be developed due to such ease and cheap process. Unfortunately, despite of various improvements on particle preheating, granulometry and usage of helium gas, the deposition efficiency (DE) remains low compared to other processes. Knowledge on the powder jet variations is then essential to understand and improve the spraying mechanisms. Thus, the aim of this study deals with the influence of the powder granulometry and the nature on the jet variation. Using experimental methods based on the jet observations (dynamic laser images), discussion is proposed for increasing the process knowledge. Spraying powders with different granulometry sizes (<10µm to 50µm) or densities using metals (copper, aluminium, tungsten) or polymers (PEEK) influence strongly the jet fluctuations and the jet size. As a result, the DE can strongly decrease according to the incident angle of the particles when impacting the substrate.