Improved Deposit Performance by Tuning of Secondary Parameters in Cold Gas Spraying of Al6061

Abstract Systematic studies on optimizing deposit performance in cold spraying mainly concern the variation in primary process parameters such as gas pressure and temperature. However, energy densities of the spray jet exposed to the deposit surface might have similar influence as substrate heating. To provide further insights, this study systematically investigates the influence of secondary parameters by robot kinematics on deposit performance. As model material, an Al6061 powder in sizes of 20-45 μm was sprayed on Al6061-T6 substrates. Fixed primary process parameter sets were adjusted for sufficiently high particle impact to critical velocity ratios. Secondary parameters were varied with respect to the stand-off distance, the traverse or spray velocity of the cold spray gun, and the line spacing. In addition, the effects of variations in powder feed rate and powder injection distance were investigated. Deposit analyses concerned deposition efficiency, microstructure, porosity, hardness, electrical conductivity and for selected conditions also deposit strengths. The results show that lower spray velocities and to some extent shorter stand-off distances lead to better deposit performance. Similarly, lower feed rates also have beneficial effects, possibly due to reaching higher particle impact energy. Apart from individual contributions, the combination of these parameters could enhance improved deposit performance, revealing potential synergistic effects among the secondary parameters. With that, this study demonstrates potentials to use careful tuning of secondary parameters as an additional way for adjusting the needed performance in cold spray to reach thresholds given in applications.