Study On Laser Cladding Technology Of Accompanying Protection For TC4 Titanium Alloy

Titanium alloy has the advantages of small density and high specific strength,which is widely used in medical and aerospace fields.However,the large friction coefficient and poor wear resistance of titanium alloy limit its application.Laser cladding is a kind of green remanufacturing technology.Coating and substrate can realize metallurgical combination,which has become an important way of surface modification of titanium alloy.The main problems in laser cladding of titanium alloy are oxidation,hydrogenation and cracks.Based on the hardware and materials,the oxidation and hydrogenation in the cladding process are effectively restrained,the formation of cracks is avoided,and the wear resistance of the cladding layer is improved.The traveling protection device designed in this paper is mainly composed of three circular air channels,the inner circular air channel is mainly used to bind the powder and protect the molten pool,the middle air channel is used to protect the area above 600℃,and the outer air channel is used to isolate the air.The surface quality of the cladding layer is the best when the accompanying protective air pressure is 0.3MPa.The advantage of the accompanying protection device is that it consumes less protective gas and can repair and protect the parts that are difficult to disassemble on site.The accompanying protective device designed in this paper is mainly composed of three circular air flows:the inner circular air flow is used to bind the powder and protect the molten pool;the middle air flow is used to protect the area above 600℃ and inhibit oxidation;the outer air flow is used to remove air.The results show that the gas consumption of the traveling protection device is small,and it can be used for laser cladding and remanufacturing of titanium alloy parts in an open environment.Based on the traveling protection device,this paper designs and optimizes the titanium alloy powder for laser cladding.The results show that when the laser power is 1750W,the scanning speed is 6mm/s,the powder feeding rate is 8g/min,the preheating temperature is 400℃,and the cladding powder Al2O3-SiC-Ag-Ti ratio is 2.5:0.5:10:87,the cladding layer with good quality can be obtained.Through the analysis of microstructure,microhardness and wear resistance of the cladding layer,it is found that nano-Al2O3 particles can effectively prevent grain growth,refine grains and play a role of dispersion strengthening during the solidification process of the molten pool;Ag and SiC can effectively reduce the β phase transition temperature and expand the β phase area,and the cladding layer is mainly composed of β strip structure and β sheet layered structure,which can effectively improve the strength of the cladding layer.