Low-pressure Cold Spraying Aluminum-based Composite Coating On The Surface Of AZ31B Magnesium Alloy And Its Performance

In this paper,Al-Al₂O₃ and Al-Ti-Al₂O₃ aluminum substrate composite coatings were prepared on the surface of AZ31B magnesium alloy by low pressure cold spraying technology,using different content of Al₂O₃ powder,Ti powder and Al powder as mixed powder,and Al-Ti-Al₂O₃ coating was heat treated with different process parameters,and the morphology,composition,mechanical properties and corrosion resistance of the coating were characterized.It provides theoretical support for the low-pressure cold spraying heterogeneous material repair technology on the surface of AZ31B magnesium alloy.The morphology,composition and microstructure of Al-Al₂O₃ coating were observed by SEM,EDS and XRD.The bonding between Al-Al₂O₃ coating and substrate is good.The addition of Al₂O₃ can significantly reduce the porosity of the coating,There is no large gap and powder agglomeration.The residual stress on the coating surface increases with the increase of Al₂O₃.The mechanical properties test of the coating will improve the hardness of the coating,the wear rate of Al-Al₂O₃ coating can reach 1/7 of the substrate,and the addition of Al₂O₃ will increase the bonding strength of the coating to 40.85MPa.The addition of Al₂O₃ will improve the corrosion resistance of the coating,and the protection rate of the coating to the substrate can reach up to 89.05%.The Al-Al₂O₃ coating can still produce good protective effect on the substrate after soaking for 720h.By characterizing the morphology,composition,residual stress and microstructure of Al-Ti-Al₂O₃ coating,the deformation of Ti particles in the coating is small,and the residual stress of the coating increases with the increase of Ti content,and the residual stress is compressive stress.The addition of Ti will improve the hardness of the coating and reduce the friction coefficient of the coating.The existence of Ti particles in the coating will improve the corrosion resistance of the coating.When the mass fraction of Ti is 28%,the protection rate of the prepared coating to the substrate can reach 96.75%.The surface porosity of Al-Ti-Al₂O₃ coating decreased significantly after heating,and the residual stress of the coating decreased to the lowest after holding at 400℃for 4h.The mechanical property test results show that the bonding strength of the coating increases to50.12MPa after heating,and the wear resistance of the coating is significantly improved.The self-corrosion current density of the coating can reach 6.71E-6A/cm² after holding at400℃for 4h,and the protection rate to the substrate can reach 98.95%.