Tamping effect during additive manufacturing of copper coating by cold spray: A comprehensive molecular dynamics study
The tamping effect is of great importance for the microstructure evolution, surface roughness, and mechanical performance of additively manufactured coatings by cold spray. A good understanding of the advantages and disadvantages of the tamping effect is therefore crucial for producing high-quality coatings, unfortunately, very few studies along this direction have been conducted. In this study, a multi-particle impact model was proposed to investigate the tamping effect on the deformation behavior and morphology of Cu particles in cold spray. It was found that the tamping effect could induce a traceable change in the flattening ratio of the first coating layer, which served as a reliable indicator for identifying the critical velocity. By continuously flattening the particles, the tamping effect led to a denser microstructure of the under-layer coating, although such a densification effect would become weaker with the increase of coating thickness. At a high impact velocity, the obstruction and extrusion of surrounding particles were not ignorable, as these interactions could significantly affect the thickness and shape of the central coating and thus affect the overview surface quality of additively manufactured copper coatings. In addition, the particles with a higher impact velocity exhibited a stronger tamping effect during cold spray, which resulted in a higher risk to penetrate the coating with potential damage to the substrate.
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