A Study On Reactive Brazing Of Alumina Ceramics In Air

Because of the excellent heat resistance, wear resistance and corrosion resistance. Alumina ceramic has broad applications in manufacturing industries. It is well known that joining of alumina ceramics is difficult. However, it is one of the key technologies for many practical applications.With Ag72Cu28 as brazing material, this thesis the auxiliary effect of TiO2 and CuO in the brazing of alumina ceramics to alumina ceramics in an oxidizing atmosphere. Three aspects of the work have been done.Firstly, when TiO2 is used as auxiliary agent, the major process parameters are TiO2 content, brazing temperature and holding time, which are the most critical influences affecting the joint strength. The optimum parameters are: TiO2 content is 5 wt.%, brazing temperature is 1080℃and holding time is 10 min. The maximum joint shear strength is 24.91 MPa. The phases in the interface of the brazing seam are CuAl2O4, TiO, TiO2, CuO and Cu3TiO4.Secondly, when CuO is used as auxiliary agent the major parameters in affecting joint strength are CuO content, brazing temperature and holding time. The maximum shear strength is 39.04 MPa when brazing temperature is 1050℃, holding time is 10 min and CuO content is 10 wt.%. The major phases in the interface of the brazing seam are CuO, CuAl2O4 and CuAlO2.Finally, the wetting effect study shows that the infiltration ability of Ag72Cu28 metal filler to alumina ceramic increases significantly, when the oxide wetting agents(such as TiO2 and CuO) are used. Base on the results of SEM, EDS, XRD and thermodynamic principles, brazing mechanisms have been proposed with, TiO2 or CuO as wetting agent respectively.