Numerical simulation of deformation behavior of Al particles impacting on Al substrate and effect of surface oxide films on interfacial bonding in cold spraying Wen-Ya Li a, * , Hanlin Liao a , Chang-Jiu Li b , Hee-Seon Bang c , C. Coddet a a LERMPS, Universite ´ de Technologie de Belfort-Montbe ´liard, Site de Se ´venans, 90010 Belfort Cedex, France b State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi’an Jiaotong University, Xi’an 710049, PR China c Department of Naval Architecture and Ocean Engineering, Chosun University, Gwangju 501-759, Republic of Korea Received 20 October 2006; received in revised form 13 November 2006; accepted 13 November 2006 Available online 11 December 2006 Abstract In this study, a comprehensive examination of the deformation behavior of Al particles impacting on Al substrate was conducted by using the Arbitrary Lagrangian Eulerian (ALE) method to clarify the deposition characteristics of Al powder and the effect of surface oxide films in cold spraying. It was found that the deformation behavior of Al particles is different from that of Cu particles under the same impact conditions owing to its lower density and thus less kinetic energy upon impact. The results indicated that a higher velocity was required for Al particles to reach the same compression ratio as that of Cu particles. On the other hand, the numerical results showed that the oxide films at particle surfaces influenced the deformation and bonding condition between the particle and substrate. The inclusions of the crushed oxide films at the interfaces between the depostied particles inhibit the deformation. # 2006 Elsevier B.V. All rights reserved. Keywords: Cold spraying; Numerical simulation; Aluminum; Oxide film; Deformation behavior 1. Introduction A wide variety of impact phenomena is observed in many cases both in micro-and macro-scales when an object impinges on another, such as erosion of particles colliding with a solid surface at relatively low velocity, ballistic impact and penetration of a macro-body at a higher velocity causing a destruction of the impacted surface [1,2]. However, for the metallic particles of intermediate velocities, typically 300– 1200 m/s, they can adhere to the impacted surface and form a coating. This phenomenon has been discovered in the middle of 1980 s at the Institute for Theoretical and Applied Mechanics of the Siberian Division of the Russian Academy of Science in Novosibirsk and firstly reported by the Russian scientists [3]. It is now the so-called cold spraying technique. In this process, spray particles (typically 5–45 mm) are accelerated to a high velocity by a supersonic gas jet generated through a converging–diverging Laval type nozzle. A coating is formed through the intensive plastic deformation of particles impacting on a substrate at a temperature well below the melting point of the spray material. Therefore, cold spraying was endowed with some unique characteristics compared to the conventional thermal spraying processes, such as almost no oxidation and phase transformation [3]. Cold spraying has attracted world- wide interest due to its high deposition efficiency and volume production of many metallic coatings and composites [3–21], and even cermets [4,5] and nanostructured coatings [5,6]. Although the impact phenomena have been studied for a long time by both numerical and experimental methods [1,2], the actual bonding mechanism for cold spray particles is still not well understood under the recent focus of investigations [3– 21]. The most prevailing hypothesis is that plastic deformation may disrupt thin surface films, such as oxides, and provide intimate conformal contact under high local pressure, thus www.elsevier.com/locate/apsusc Applied Surface Science 253 (2007) 5084–5091 * Corresponding author. Tel.: +33 3 84583160; fax: +33 3 84583286. E-mail address: wenyali_cn@hotmail.com (W.-Y. Li). 0169-4332/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2006.11.020