Ablation laser and heating laser combined to cold spraying

Cold spraying is particularly suitable for the elaboration of coatings sensitive to heat and oxidation. As spraying particles are not subjected to melting, the adhesion and formation of the coating is due to the kinetic energy transmitted to the particles by accelerating gas. Bonding mechanisms are not only strongly dependent on the particle velocity but also on the state of the substrate surface. The presence of surface pollutants inhibits the coating elaboration. Surface modifications are necessary to reach a high adhesion between the coating and the substrate. A laser ablation and a laser heat treatment are proposed to prepare the substrate prior to cold spraying. Ablation laser is used to eliminate adsorbed pollutant molecules and heating laser is employed to improve the contact between substrate and particles and coating substrate adherence. The bonding of aluminium coating on aluminium 2017 alloy was evaluated by tensile adhesion tests and demonstrated the strong influence of the laser treatments in comparison with conventional processes (grit blasting and degreasing).