Microstructure and Properties of 7075/Al2O3 Composite Coatings Prepared by Supersonic Laser Deposition

Supersonic laser deposition is an innovative surface treatment technology, which combines supersonic cold spray technology and laser irradiation heating technology. It has the advantages of preparing hard metal composite coating with high deposition efficiency. In this work, composite coatings of hard 7075 Al alloy and Al2O3 ceramic particles were prepared on 7B04 Al alloy substrate by supersonic laser deposition technology. The effect of laser power on the deposition characteristics and mechanical properties of coatings was systematically studied. The microstructure, phase composition and microhardness of the coating were characterized and analyzed by field emission electron microscope (SEM), energy dispersive analyzer (EDS), X-ray diffractometer (XRD) and microhardness tester. The results show that with the increase of laser power, the thickness, density, deposition efficiency, hardness and the dispersion uniformity and deposited amount of Al2O3 particles in the coating increase. When the laser power is 600 W, the coating thickness reaches to 1543 mu m, the coating porosity is only 0.05%, the relative deposition efficiency of Al2O3 particles is 65%, and the coating HV hardness rises to 1911 MPa. However, when the laser power is enhanced to 900 W, the thickness and deposition efficiency of the coating slow down, and the porosity increases significantly. The oxidation of coating materials is found, and the relative deposition efficiency of Al2O3 particles and the coating hardness decrease significantly. In summary, the appropriate amount of laser input is beneficial to improve the plastic deformation of aluminum alloy particles, resulting in significant enhancement of coating quality, while the excessive laser input leads to softening of aluminum alloy particles and even oxidation of powder materials, which deteriorate the quality of deposited coatings.