Molecular Dynamics Simulation of Au Cluster Depositing on Au Surface in Cold Gas Spray

Cold gas spray is a relatively new coating technique by which coatings can be formed without significant heating of the sprayed powder. In contrast to the conventional thermal spray processes, such as flame, arc, and plasma spraying, in cold spraying there is no melting of particles prior to impact on the substrate. In cold spray, particles are accelerated to a very high velocity by a flowing gas with supersonic speed and the temperature of spray particles is much lower than its melting point. However, being accomplished in so short an interval, the impact and deposition processes are difficult to be observed by experimental ways. Using molecular dynamics simulation, the deposition of nano-scale Au clusters on Au (001) surface was studied. The many-body potential is used to simulate the interatomic force between the atoms. By taking “snapshot”, the impact, deposition process and the final appearances of the cluster and the substrate were observed directly. It is found that both the substrate and the cluster deform and lose the crystalline structure. But after reconstruction and relaxation, both of them recover the crystalline structure. By calculating the temperatures of the substrate and the local area influenced by impinging, it is found that the melt phenomenon occurs during impact and deposition, whereas the temperature of the rest region of the substrate is still below the melt point. In addition, the influence factors on deposition, such as incident velocity and the size of the cluster, are discussed in the paper. Simulation results show that the higher incident velocity or the larger size of the cluster could result in stronger interaction between the substrate and the cluster owing to the higher kinetic energy of the cluster.