The Research Of Laser Welding Process Of Titanium,Steel And Ceramic Dissimilar Materials

Titanium(Ti)alloy has high specific strength,high temperature resistance,low density and good corrosion resistance,but its higher price,processing and welding properties are poor,so that the development of Ti alloy is greatly restricted.Stainless steel(SS)is the most commonly used structural material,with good mechanical properties,welding properties,processing properties,and cheap,but its specific gravity is larger,corrosion resistance is not as good as Ti alloys.High hardness,good wear resistance,outstanding resistance to rust,high thermal and chemical resilience in ceramics,while ceramics have the characteristics of brittleness,ductility and poor processability,which are prone to fracture during use,and it is difficult to prepare vast sizes of complex materials,limiting the engineering applications of ceramics.The use of composite structures of diverse materials should supplement one another,with broad application perspectives and research importance,to achieve the economic and performance benefits of both materials.To this end,this paper carried out a study of laser welding process of titanium,steel and ceramic heterogeneous materials.This paper presents a new welding process for heterogeneous materials.First,the effect of the microstructure of the laser welded joints of TC4 alloy and 304 SS by various intermediate layers was investigated.When Sn Pb brazing material was used,the main organization of the brazed welds was Fe₃Sn+Fe₃Sn₂,(?Sn,Pb),(?Sn)+Sn₂Fe and(?Sn)+Sn₃Ti₂.The joints fractured at the brazed welds with a maximum tensile strength of 108 MPa.When Cu Zn Sn Si brazing material was used,the formation of(Fe,Zn)+Fe₃Zn₇,?-Cu Zn and?-Cu Zn+Ti₂Zn₃ as the main organization of the brazed welds.The joints fractured at the brazed welds with a maximum tensile strength of 210 MPa.when a pure Ni interlayer was used,the welds contained mainly(?Fe,Ni),?-Ti+Ni Ti₂+Fe₂Ti,and Ni₃Ti+Fe₂Ti phases.The brittle and hard intermetallic Ti-Fe is generated in a joint,with a tensile strength of 178 MPa in the joint.The joint output thus depends principally on the properties of the interlayer material and the compound layer organization in the weld.In order to further improve the mechanical properties of laser welded joints of Ti/steel dissimilar materials,the effect of laser power on laser welded joints of TC4 alloy and 304 SS was studied.When the laser is focused on SS,with the increase in laser power,the width of the melt weld gradually increases,the width of the unmelted SS gradually decreases,the peak temperature on both sides of the intermediate layer interface increases linearly,the equivalent force of the joint generally shows a trend of first decreasing and then increasing,and the tensile strength of the joint first increases and then decreases.The performance of the joint changes more obvious.Therefore,the optimization of laser welding process parameters to improve the weldability and mechanical properties of Ti/SS joints is feasible.Second,the study of different welding structures of Ti/SS laser welding.When the Cu transition layer was laser welded with Cu Zn brazing material,the main organization of the fusion weld was?-Fe and Cu(s,s)phase,and the main microstructure of the brazed weld was?-Cu Zn,?-Cu Zn+?-Cu,Cu Ti+Ti₂Zn phase,and the joint's strength came to 108MPa.For the welding of the structure a mechanical screw was used with the Cu transition layer.It was found that the presence of the screws had little effect on the joints'microstructure.The joint's tensile strength reached 199 MPa,which improved some of the mechanical properties of the joint.The welding capacity and mechanical properties of the Ti/SS joint are therefore improved by optimizing the structure of the solder.Finally,the welding process was attempted to connect titanium,steel with ceramics,and an effective connection between TC4 alloy,304 SS and Al₂O₃ ceramics was successfully achieved,and the connection mechanisms were all diffusion welding.The method was able to avoid as much as possible the damage to the ceramics from heat sources and reduce the possibility of thermal cracking inside the ceramics,which is key to the control of heat input.Therefore,this welding process has special advantages in the field of joining metals to ceramics.