Aluminum powder particles were deposited on medium carbon steel substrate by cold spraying process. High resolution observation showed that the particles were severely deformed in solid state, whereas the substrate was hardly deformed. Furthermore, the particles were not bonded intimately to the substrate, and most of all, oxygen as well as thin gap were clearly detected along the interface of particle/substrate. Based on the observations, the impacting behavior of a particle on a substrate as well as the influence of the oxide film was modeled. The oxides covering the surface of metallic powder particles and the substrate significantly affect the impact and deformation behaviors of particle and substrate, and consequently the values of strain, stress, and temperature at the interface in the numerical simulation. (C) 2015 Elsevier B.V. All rights reserved.