Structural Characteristics And Wear Behavior Of Laser Cladding Zirconium Based Coating On Titanium Alloy Surface

TC4 titanium alloy has been widely used in aerospace,Marine ships,petrochemical and other important fields due to its low density,light weight,high specific strength and strength ratio,good corrosion resistance and other excellent properties.However,due to the inherent defects of low hardness and high wear coefficient of titanium alloy,its further application is limited.The results show that it is an effective method to prepare a composite coating with high hardness and wear resistance on the surface of titanium alloy by laser cladding.Zr-base alloy has high hardness,high wear resistance and other excellent properties due to its unique structure.Therefore,the preparation of Zr-based composite coating on the surface of TC4 titanium alloy by laser cladding technology is expected to improve the surface hardness and friction and wear properties of titanium alloy.In this thesis,based on Zr₅₅Cu₃₀Al₁₀Ni₅ alloy system,Si C,Ti C,Si₃N₄ particles reinforcing phase and B elements were added,and Zr matrix composite coating with good performance was prepared on the surface of TC4 titanium alloy by laser cladding technology.The microstructure and phase composition of Zr matrix composite coating were characterized by XRD,OM,SEM and EDS.The solidification characteristics and formation mechanism of the coating were studied.The microhardness and tribological properties of the coating were tested by microhardness tester and friction tester,and the mechanism of improving the coating's tribological properties was analyzed.The following conclusions are drawn:There is good metallurgical bonding between the cladding coating and TC4 matrix without obvious cracks and pores.Zr-based composite coating is mainly composed of Cu₁₀Zr₇,Ni₁₀Zr₇,Cu Zr₂,Al₂Zr₃ and other Zr intermetallic compounds,?-Zr and Zr,Al oxide phase.The microstructure at the bottom of the coating was columnar grains grown epitaxically,and the top of the coating had dispersed petal-like microstructure.The microstructure of the coating was obviously changed by adding particle reinforcing phase.The microhardness of the coating increased obviously by adding particle reinforcing phase.The maximum hardness of Zr₅₅Cu₃₀Al₁₀Ni₅ composite coating is 969 HV_0.1.After the addition of element B,the hardness of the coating reaches the maximum value of 1280 HV_0.1,which is 3.5times of the hardness of titanium alloy matrix.Average wear coefficient of Zr₅₅Cu₃₀Al₁₀Ni₅composite coating and cladding coating doped Si C,Ti C,Si₃N₄,B particle reinforced phase is0.6533,0.7122,0.4963,0.6566,0.6092,0.6583,0.5631,respectively.The main wear mechanism of the coating is abrasive wear and adhesive wear.