Formation and microstructure analysis of titanium/steel composite layer with copper transition layer by blue laser coaxial cladding

During the welding repair of titanium-steel composite plates, it is difficult to effectively form the copper transition layer. To address this issue, the use of a blue laser to increase copper’s absorptivity was proposed. The effects of laser power, powder feeding rate, and scanning speed on copper powder melting and copper layer formation parameters were investigated. The influence of different process parameter combinations on the diffusion behavior of iron elements at the Fe-Cu interface was analyzed using an energy dispersive spectrometer (EDS) area scanning. During coaxial cladding of a titanium layer onto the copper surface, the melting behavior of the copper layer under blue laser irradiation was analyzed. Subsequently, the microstructure and mechanical properties of the Fe-Cu-Ti joint were investigated. The results show that blue laser irradiation enables efficient melting of copper powder. As laser power increases, the melting width, weld reinforcement, melting depth, and dilution rate of the copper layer all increase. As the powder feeding rate increases, the melting width and weld reinforcement of the copper layer increase, while the melting depth and dilution rate significantly decrease. As scanning speed increases, both the formation parameters and dilution rate of the copper layer exhibit decreasing trends. EDS area scanning of Fe-Cu joints demonstrates that controlling copper layer thickness significantly reduces iron element content in the upper surface region, avoiding the formation of brittle Fe-Ti intermetallic compounds. The formed joint is mainly composed of TiCu and Ti₃Cu₄ intermetallic compounds. Fe-Ti intermetallic compounds that have not formed brittleness. The average hardness of the copper titanium mixed zone is 326HV0.2.