Structure and Wear Resistance of CuZn35 Coating Prepared by Cold Spraying

CuZn35 brass has high strength and toughness, excellent thermal conductivity, electrical conductivity and corrosion resistance, so it is widely used as a protective coating in thin-walled tubes and turbine blades. At present, CuZn35 coatings are usually prepared by arc spraying, which has high porosity and poor wear resistance. Cold spraying is a promising coating deposition technique for fabricating anti-wear composite coatings. However, up to now, there are few studies on the preparation of CuZn35 coatings by cold spraying method. Cu/Zn mixed powder was often used in the preparation of CuZn coatings, and the composition uniformity and wear resistance of the coatings were poor. During the cold spraying process, the particle temperature before deposition was one of the most important parameters for achieving high-quality coatings. In the present study, by using CuZn35 alloy powder instead of mixed Cu/Zn powder, non-oxidized, density and anti-wear CuZn35 coatings were prepared by high pressure cold spraying. Further, the effect of accelerated gas temperature used during cold spraying on the microstructure and properties of CuZn35 coatings was explored. The CuZn35 coating was deposited on the 100 mm × 100 mm × 5 mm aluminum plate by high pressure cold spraying system. By changing the gas temperature parameters during the cold spraying process, the effect of accelerated gas temperature on the microstructure and wear resistance of the cold sprayed CuZn35 coating was investigated. Three kinds of CuZn35 coatings were prepared by cold spraying under the conditions of pressure of 5 MPa and accelerated gas temperature of 400, 600 and 800 ℃. Compared with as-cast CuZn35 material, the wear resistance of these coatings was evaluated by rotary friction and wear test under a load of 2 N. The cross-section microstructure of the coatings was analyzed by optical microscope (OM). Scanning electron microscope (SEM) and 3D Profiler were used to analyze the coating microstructure and wear surface morphology. The results of this study showed that the CuZn35 coating could be directly deposited on the surface of aluminum substrate by cold spraying with CuZn35 alloy powder. The particles inside the coating were fully deformed and tightly bonded. The accelerated gas temperature in the cold spraying process had a great effect on the structure and mechanical properties of the coating. With the increase of cold spraying accelerating gas temperature, the deformation of particles in CuZn35 coating increased, and the bonding between particles was better. As a result, the porosity of CuZn35 coating decreased from 2.67% to less than 0.5% with the acceleration gas temperature of cold spraying increasing from 400 ℃ to 800 ℃. Accordingly, the hardness increased from 200HV0.3 to 242HV0.3 with the increase of gas temperature. The wear resistance of the cold sprayed CuZn35 coating increased significantly with the increase of accelerated gas temperature during the deposition process. With the increase of gas temperature from 400 ℃ to 800 ℃, the wear rate of the coating decreased from 3.67 mm3/(N·mm) to 1.80 mm3/(N·mm). The wear resistance of the CuZn35 coating prepared by cold spraying at 800 ℃ can reach the level of as-cast CuZn35 material. With the increase of accelerated gas temperature during cold spraying, the defects such as pores and microcracks of CuZn35 coating are significantly reduced, the bonding between coating particles is enhanced, and the hardness of the coating is gradually increased. In the friction and wear experiment, the wear resistance of the coating is significantly enhanced with the increase of accelerated gas temperature during preparation. © 2023 Chongqing Wujiu Periodicals Press. All rights reserved.