In cold spraying, for successful bonding powder particles have to exceed a critical velocity upon impact, which is dependent on properties of the particular material. So far a detailed physical explanation of the underlying mechanisms of bonding is still lacking. In the present study, computational materials science and high resolution microscopical methods are used to investigate the microstructural development at the particle-substrate interface. The modelling can show that the critical velocity is related to a transition in the flow-behaviour on the particle or substrate surfaces. The presence of microstructural features predicted by modelling in detail could be confirmed by SEM and TEM analyses of internal interfaces of cold sprayed coatings. By describing the mechanisms of bonding, the calculations could also demonstrate the influence of material properties or microstructural defects on the conditions for successful impacts. With respect to particular powder properties, the results should promote the development of optimum process parameters in cold spraying.