Microstructure and improved anti-corrosion properties of cold-sprayed Zn coatings fabricated by post shot-peening process

Abstract To improve the corrosion resistance of Mg alloy, Zn coating was formed by cold spraying technology followed by post shot-peening processing. The phase structure, microstructure, and corrosion properties of the cold-sprayed Zn coatings before and after shot peening process were all investigated. The cold-sprayed Zn coating presented a porous and roughness structure. However, the Zn coatings after shot peening illustrated densifications with flattened and elongated Zn particles on the top layer. The mass and thickness losses of Zn coatings after shot peening both increased with the impact pressure owing to the competition between the densification and the erosion of Zn coatings. The microhardness of Zn coatings after shot peening increased from 40 HV0.025 to 64 HV0.025 due to factors like densification structure, work hardening, and grain refinement. It also displayed decreasing profiles from the surface to the inner bulk. The anti-corrosion properties of Zn coatings after shot-peening were improved by about one fold when compared to the cold-sprayed Zn coating owing to the presence of compact top layers. The corrosion changes in behaviors of Zn coatings before and after shot peening were clarified by comparing the morphologies and phase structures after immersion in stimulated body fluid. In sum, the proposed simple post-processing strategy looks promising for improving the corrosion resistance of cold-sprayed Zn coatings modified Mg alloy substrates, which might be useful for future use in bone implants.