Joining of C_f/SiBCN composite with two Ni-based brazing fillers and interfacial reactions

G/SiBCN ceramic composite was joined using Ni-19Cr-10Si （BNi5） and Ni-33Cr-24Pd-3.5Si-0.5B filler alloys at 1170 ℃ for 10 min. Two kinds of Ni-based filler alloys exhibited good wettability on the CdSiBCN com- posite, with a contact angle of 13° and 4°, respectively, The microstructures of the brazed joints were investigated by electron-probe microanalysis （EPMA）, and three-point bend test was conducted for the joints at room temperature. When being brazed with BNi5 filler alloy, no evident reaction layer was ob- served at the surface of the joined composite, and the joint microstructure was characterized by Ni2Si matrix with scatteringly distributing mixture compounds of Cr23C6, Ni2Si and CrB. While Ni-Cr-Pd（Si,B） brazing alloy was used, a Cr23C6 reaction layer with a thickness of 11 μm was formed at the surface of the base composite. In the central part of the brazed joint, the phases were composed of Ni（Cr, Si） solid solution and complex compounds including Pd2Si, （Ni,Pd）2Si and Ni-B. The strength of Cf/SiBCN joint brazed with BNi5 filler alloy was 62.9 MPa at room temperature, whereas that with Ni-Cr-Pd（Si,B） filler alloy was at the same level.

Microstructure and Property of AlN Joint Brazed with Au–Pd–Co–Ni–V Brazing Filler

An Au-Pd-Co-Ni-V brazing alloy was designed for AIN ceramic joining. Its wettability on AIN was studied with the sessile drop method. The results showed that the contact angle was decreased gradu- ally with increasing temperature and the prolonging of holding time. Sound AIN/AIN joints were achieved with the brazing alloy at 1170 ℃ for 10 min. The microstructure of the AIN/AIN joints was examined by scanning electron microscopy （SEM）. It was found that element V played the active role in the interfacial reaction between the ceramic and the brazing alloy, V reacted with N decomposed from AIN, resulted in the formation of V-N compound. Based on the energy-dispersive spectroscopy （EDS） and X-ray diffraction （XRD） analysis results, the V-N reaction product was verified as V2N. The overall reaction during the brazing process can be described by the following equation： 2V ＋ AIN ＋ 2Pd = V2N ＋ Pd2AI. The AIN/AIN joints brazed with the Au-Pd-Co-Ni-V brazing alloy exhibited three-point bend strength of 162.7 MPa at room temperature, and under the bend test the fracture of the joint occurred at the AIN ceramic substrate.