Dry Surface Preparation Using Supercritical Cryogenic Nitrogen Jet Improves the Adhesion Strength of Cold Gas Sprayed Coatings (SCNCS)

The adhesion performance of Cold Sprayed coatings depends on the quality of the substrate [1,2,4,8]. Before deposition, the surface of substrate must be prepared to a specific required quality, which promotes the anchoring of sprayed coating. Grit Blasting (Samson et al.) [1] is known as the conventional surface preparation before Cold Spraying. But such method causes issues: a) shallow roughness, which does not strengthen bonds between layer and substrate; b) embedment of particles in the substrate, which creates discontinuity of the material at the interface and causes cracks that degrade the layer. Recently, Laser [2] and Pulsed Water Jet (PWJ) [1] have been tested as substrate preparation methods. These methods have shown their ability to generate improved roughness without particle embedment. PWJ has particularly shown interest in Al substrate to generate crevices, which are anchors for the Cold Sprayed coatings. Nevertheless, Laser affects thermally the substrate and induces constraints that may disadvantage the coating quality. PWJ generates liquid effluents. Besides some substrates such as ferrous metals can react with oxygen of water leading to corrosion and coating adhesion weakness.