Effect of the Compressed Layer on Final Impacting Velocity of Submicron Size Particles in Cold Spraying by Computational Methods

To overcome the deceleration effect of compressed layer, a needle shape barrier is placed before the substrate to change the structure of compressed layer, subsequently make this region suitable for accelerating submicron particles. And computational simulation method was used to examine the gas solid two phase flow around the needle. A compressed layer before the substrate can decelerate the impacting velocity to nearly 80 m/s for submicron particles with diameter less than 0.5 um. A sharp needle barrier can destroy the compressed layer before the substrate, it can change the thickness of compressed layer and direction of the gas flow ahead of the substrate, subsequently elevate the final impacting velocity. The results obtained from the computational simulation indicate that it is applicable to deposit submicron (larger than 0.5 um) copper particles directly using cold spraying, but further experiment should be done to verify these results.