Influence of stand-off distance and pressure in copper coatings deposition efficiency and particle velocity

The effect of particle velocity on deposition efficiency and microstructure of copper powder on aluminum alloy substrates using Low Pressure Cold Spray (LPCS) is here reported. For this, experimental substrate-coating systems were fabricated varying powder feed rate, transverse speed, and air pressure keeping the compressed air, substrate temperature, and stand-off distance constant (600 degrees C, 100 degrees C, and 5 mm, respectively). From the combination of low feed rates and low transverse speed, deposition efficiency tends to increase. The maximum deposition efficiency of 34.8% was obtained for a feed rate of 0.2 g/s, 10 mm/s transverse speed, and 8 bar of air pressure. The pressure and stand-off distance effect on coatings was studied measuring the particle velocity with and without substrate. For this, spraying conditions were varied between 5-8 bar and 5-15 mm, respectively. Experimental measurements were compared with results from computational fluid dynamics simulation to understand the effect of the spraying parameters on the complete powder size distribution. The highest deposition efficiencies (36-37.5%) were obtained at 7 bar air pressure for spray distances between 5 and 12.5 mm. Increasing the pressure to 8 bar led to a decrease in the deposition efficiency (6-11%). The tendency of deposition efficiency seems to match with the in-flight particle velocity influenced by the presence of a substrate, which serves as evidence of the bounce-off effect. The reduction of the particle velocity, along with the low transverse speed seems to remove less attached particles by erosion through the peening effect.

Automated summary

The effect of particle velocity on the deposition efficiency and microstructure of copper powder on aluminum alloy substrates using Low Pressure Cold Spray (LPCS) was investigated in this study. It was found that low feed rates and low transverse speeds tend to increase deposition efficiency. Additionally, the pressure and stand-off distance also influenced the coating quality, with optimal deposition efficiency observed at specific air pressures and spray distances.