Preparation And Research Of Low-Pressure Cold Sprayed Copper-Based Composite Coating On Aluminum Alloy Surface

7075 aluminum alloy is widely used in the aerospace field because of its good performance,but its service conditions are harsh and it is easy to fail due to corrosion,wear and other reasons.The failed aluminum alloy parts are repaired and remanufactured to restore their service performance and reduce resource waste.Therefore,this paper uses supersonic low-pressure cold spraying to deposit Cu-Ni composite coating and Cu-Ni-Al₂O₃composite coating on 7075 aluminum alloy surface to improve its mechanical properties and corrosion resistance,and to extend its service time.In this paper,Cu-Ni composite coating is prepared by changing nickel content.The coating has good compactness and no obvious defects such as holes.EDS and XRD tests show that the sprayed powder did not oxidize or form Cu-Ni alloy;With the increase of nickel content,the microhardness and adhesion of Cu-Ni composite coating gradually increased,and the microhardness of Cu-40%Ni is 130.94HV_0.1.The binding force is lower than 10MPa;The wear mechanism of Cu-Ni composite coating is fretting wear,and the wear resistance of Cu-Ni composite coating increases with the increase of nickel content;The corrosion resistance of Cu-30%Ni coating reaches the best state.After soaking for 30days,the self corrosion current density can reach 3.34×10^-8A/cm²。In this paper,Cu-Ni-Al₂O₃ composite coating is prepared by doping Al₂O₃ with different mass fraction in Cu-30%Ni coating,and the compactness of the coating is improved.EDS and XRD tests show that the actual alumina content in Cu-Ni-Al₂O₃composite coating is much lower than that in spraying mixed powder,and the alumina content in Cu-Ni-40%Al₂O₃ coating is only 6.07%;With the increase of alumina content,the microhardness of Cu-Ni-Al₂O₃ composite coating increases first and then decreases,and the adhesion of Cu-Ni-40%Al₂O₃ coating increases.The maximum wear resistance of Cu-Ni-40%Al₂O₃ coating is 28.74MPa,and the wear mechanism is still fretting wear;The corrosion resistance of Cu-Ni-30%Al₂O₃ coating is the best,but the coating will crack due to stress corrosion after soaking for 60 days,resulting in coating failure.In this paper,Cu-Ni-30%Al₂O₃ coating is heat treated by changing temperature.The residual stress test shows that the doping of hard phase Al₂O₃ increases the residual stress of the coating,and the residual stress of the coating can be significantly reduced by heating;With the increase of heating temperature,the microhardness of Cu-Ni-30%Al₂O₃ coating surface gradually decreases and the coating adhesion gradually increases.It reaches the maximum value of 30.98MPa at 450℃,and the wear resistance first decreases and then increases.At 350℃,the wear resistance of the coating reaches the best,and its volume wear rate is 3.34×10^-9m³/m,the wear mechanism is fretting wear.It is found that the hardness of the coating decreases with the increase of the distance from the interface between the coating and the substrate to one side of the coating;Appropriate heat treating temperature is conducive to improve the corrosion resistance of Cu-Ni-30%Al₂O₃ coating.The corrosion resistance of the coating reaches the best at 350℃.After soaking for 60 days,the heat-treated Cu-Ni-30%Al₂O₃ coating does not produce stress corrosion cracks,and the corrosion products of the coating are more uniform and compact at 350℃,the corrosion morphology is more uniform and flat,showing good corrosion resistance.