Impact of spray angle and particle velocity in cold sprayed IN718 coatings

Cold spray (CS) deposition has potential applications in repair technology or additive manufacturing due to its ability to operate at low temperatures, achieve high deposition rates, and produce thick, dense coatings. For adoption of CS in repair applications, it is crucial to evaluate the influence of spray angles since geometry of repair zones are typically complex and non-flat. In this work, we investigated the influence of spray angles and particle velocities on the cold spray deposition of Inconel 718 (IN718) powder particles using N2 as propellant gas. Three oblique spray angles including 50, 60 and 70° were compared with the 90° normal spray angle for cold spray deposition of IN718 powders on Al6061 substrate. Three sets of cold spray parameters at each spray angle, giving particle velocities from 820 to 920 m/s were employed to study their effect on the coating properties. Particle velocity was found to have greater impact on coating porosity compared to spray angle. Coating with lowest porosity and lowest surface roughness but highest compressive surface residual stress was achieved with deposition at lowest spray angle (50°) and highest particle velocity (920 m/s). Changing the spray angle has greater influence on the deposition efficiency, with thickest coating observed at normal spray angle of 90° across all three cold spray conditions. Finite element method (FEM) simulations were also performed to understand the influence of powder and substrate temperatures on critical angles for bonding. The simulation results suggest that elevating the powder temperature is likely to cause a slight increase in the critical bonding angle.