Particles may rebound from a substrate surface during cold spraying, which affects the quality of the coating. In this paper, the rebound phenomenon and its consequences on deposition behavior have been analyzed using the finite element analysis software ANSYS/LS-DYNA version 970. In a range of particle velocities of 50-1000 m/s, increases of the impact velocity caused a rapid decline of the rebound coefficient R to a low point Rmin. After that, R began to rise slowly. Then the effect of the impact velocities and material properties on the rebound phenomenon were analyzed. Both the material strength and density influenced this rebound phenomenon. Four stages of the impact process and a model of strain distribution were proposed in detail to explain the rebound phenomenon.
Xianglin ZHOU Xiangkun WU Jianguo WANG Jishan ZHANG
Cold spray technology,originated from the Institute of Theoretical and Applied Mechanics Siberian branch of the Russian Academy of Sciences,is a rapidly emerging industrial coating technology.Cold sprayed particles with high-velocity impact onto a substrate so as to induce severe plastic deformation and then create a deposit.For its low temperature and high velocity compared with thermal spraying,the cold spraying process is increasingly used in the industries for protective coating.The deposition characteristics of the particles,coating formation and bonding mechanism of the cold spraying process are different from thermal spraying.Many theory investigations of the cold spraying process contribute to the development of the high performance coatings,which makes the cold spraying process as a popular research field.Presently,the deposition characteristics,bonding mechanism,process optimization as well as classical applications of the cold spraying technology in the past are reviewed,and the interesting points for the further development,optimization and applications of this technology are also recommended.
In the practical cold-spraying process, a number of particles impact onto a substrate and then form a coating. To study the deformation behavior and multi-particle interactions, single-particle, two-particle, and three-particle impacts were simulated using the ANSYS/LS-DYNA version 970. A copper coating was prepared and scanning electron microscopy （SEM） was employed to analyze the microstructures of the powders and the coating. Numerical results reveal that the critical deposition velocity is 600 m/s for a copper particle/copper substrate. The particles deform more fully due to multi-particle interactions, such as tamping, interlocking, and extrusion effects. The compression ratio increases from 40% to 70% as a result of the tamping effect. This is beneficial for achieving the cold-sprayed coating. The multi-particle morphology and compression ratio in the experiment are consistent with those of simulation results. Based on these results, the coating of high performance can be prepared through selecting appropriate parameters and suitable pre-treatment processes.
Xiang-lin Zhou Xiang-kun Wu Hui-hua Guo Jian-guo Wang Ji-shan Zhang
