This paper aims at improving the adhesive strength of SS 316L coating by substrate preheating (400, 600 and 700°C). The relationships between the adhesive strength of coating/substrate interface and the substrate preheating temperature are discussed. It was found that stronger adhesion is able to occur despite the presence of a thick oxide film on the substrate surface. The preheated substrate surface undergoes a stronger plastic deformation that disrupts the oxide films for obtaining an intimate contact between particle and substrate material. In addition, the oxide films on the substrate surface can prevent the generation of material jet of the substrate. The effects of substrate preheating on the microstructure and hardness were also investigated.

In the present investigation, Al5056 alloy-based metal matrix composites having SiC particles of different sizes were prepared by cold spraying. The average particle sizes of the used SiC feedstock varied from 66.94 µm to 1.64 µm. The calculated results by the FLUENT software show that the velocity of SiC particle decreases with the increase of the particle size, while the kinetic energy is greatly increased with increasing the particle size. The addition of SiC particles effectively reduces the porosity of the composite coatings. Furthermore, the porosity of the composite coatings increases with the decrease of SiC particle size, while the content of SiC in the coatings decreases with the decrease of SiC size. In addition, two effects of SiC particles determine the coating properties, i.e., the advantageous peening effect and the disadvantageous effect that reduces the effective contact between the coating and substrate.