Effect of particle shape on mechanics of impact in the deposition of titanium nanoparticles on a titanium substrate

We report large scale molecular dynamics simulations of the cold spray process, where the impact of single titanium nanoparticle on a titanium substrate has been studied, and the effects of particle shape are determined at the nanoscale. We simulated conical, cubic, cylindrical and spherical particles of the same mass impacting with the substrate at 800 m/s. The mechanics of impact, including stresses, strain, strain rate, flattening ratio and temperature, are determined for each particle shape. We show apparent Young's modulus dependence on particle shape. We show that the deformation, stress and temperature also depend on the particle shape. The local temperature and stress and structural changes experienced by the substrate also depended significantly on the particle shape. We found that cubic and spherical particles lead to similar behaviour, showing higher plastic deformation and flattening ratio. However, conical particles impacting with their sharp tip lead to entirely different behaviour. The conical particle undergoes lower deformation and stress, however, leaves the highest localized temperature and stresses on shallow regions near the surface of the substrate. In contrast, deeper regions of the substrate are not affected by the conical particle. A cylindrical particle with a larger width to the height aspect ratio and lower surface to volume ratio is shown to have a higher apparent Young's modulus and deforms the least. However, it leads to much deeper structural changes on the substrate, due to larger stiffness.