Study on sand erosion resistance of modified silicon carbide/polyurethane composite coatings based on selective laser melting fabricated 7075 alloy

Abstract 7075 is widely used in various fields, such as aerospace. It is often affected by sand erosion in its service environment, causing irreversible damage to parts with complex shapes. Therefore, this paper uses 7075 alloy prepared by selective laser melting as the substrate to fabricate a sand erosion-resistant coating. Silicon carbide (SiC), a material with high strength and hardness, can effectively increase the hardness and strength of polyurethane materials when added to them, thereby enhancing their resistance to wind-sand erosion. Silane coupling agents can enable the combination of polyurethane materials and their modified materials. 1-3 mm SiC powder was modified with a silane coupling agent KH-550 to improve its bonding strength with polyurethane materials, and magnetic stirring combined with ultrasonic oscillation was used to achieve uniform dispersion of SiC. The sand used in the tests has a particle size of 40-70 mesh, and the tests are carried out under an air pressure of 0.3 MPa with erosion angles of 0°, 30°, 45°, 60°, and 90°, respectively. Meanwhile, a microscope was used to observe the micromorphology and analyze the erosion mechanism. The results show that under low-angle (30°) erosion, the coating erosion is mainly caused by cutting. As the erosion angle increases, the erosion mode gradually transforms into impact and chiseling. The maximum weight loss of the SiC-reinforced coating is 0.014 g, while that of the coating without SiC reinforcement is 0.016 g. Additionally, the peak of weight loss shifts to the left, which proves that SiC improves the wind-sand erosion resistance of the coating.