Study On The Joint Of TC4Alloy And Si₃N₄Ceramic With Brazing And Laser

In recent years, the joining of metals and ceramics has become a hot topic. TC4alloy has been widely used in the aerospace field because of its excellent performance.With excellent high temperature performance, Si3N4ceramics has an important statusamong ceramic construction materials. The joining of TC4alloy and Si3N4ceramic,can not only exhibit excellent high temperature performance, but also has excellentprocessing performance of metal. The joining of metals and ceramics has widepractical value in many industrial areas.The main difficulties of the joining of TC4alloy and Si3N4ceramic are thewetting of Si3N4ceramic and the relief of the residual stress between the surface ofTC4alloy and Si3N4ceramic. This study selected Ag-Cu-Ti alloy as the filler, whichhas good ductility and high thermal expansion coefficient and successfully weldedTC4alloy and Si3N4ceramic. With the help of SEM, the morphology and structure ofthe joint were analyzed. With methods of XRD, EDS and four-point bending strengthanalytical testing, the composition, organization and structure of the joint werestudied. Thus the connection mechanism was investigated initially, and the suitableparameters of welded joints were determined. The feasibility of laser beam weldingTC4alloy and Si3N4ceramics was also explored, mainly to study the effect of thefactors, including laser power, laser scanning speed, combined with the way thesample, the middle layer.The results show that the joint of TC4alloy and Si3N4ceramic with Ag-Cu-Tifiller is influenced mainly by temperature and time. By changing the temperature andtime can control the morphology and intensity of the joint. Four-point bendingstrength of the joint at850℃for15min reaches the maximum strength of33.7MPa.The reason of the successful joint is that titanium of the filler alloy, as active elements,can wet the surface of ceramics and react with Si3N4, which forms a layer of reactionproducts at joints of both sides. Under the current experimental condition, laser beamwelding haven’t effectively achieved the joint of TC4alloy and Si3N4ceramic.