Microstructure And Mechanical Properties Of The Si₃N₄ Ceramic /42CrMo Steel Brazed With Ag-Cu Ti+WCp Composite Filler

Si₃N₄ ceramic was brazed to 42CrMo steel using Ag-Cu-Ti+WCp composite filler. Effects of brazing parameters, composite filler composition on the microstructure and mechanical properties of the joints were analyzed by means of SEM, EDS and XRD.The joint brazed using Ag-Cu-Ti+WCp composite filler is comprised by three regions: The TiN and Ti5Si3 double reaction layer of Si₃N₄/brazing alloy, layer of TiN close to Si₃N₄ ceramic, layer of Ti5Si3 close to brazing alloy; The Fe2Ti and FeTi double reaction layer of 42CrMo/brazing alloy, ayer of Fe2Ti close to 42CrMo steel, layer of FeTi close to brazing alloy; The Ag and Cu based solid solution in the mid of the joint together with WCp and Cu-Ti compound among them. The optimum brazing parameter is 1173K at 10min, the maximal bending strength of the joint brazed with (Ag72Cu28)96Ti4+15vol.%WCp composite filler was up to 361.2MPa in this situation.When the Si₃N₄ /42CrMo were brazed with (Ag72Cu28)96Ti4+5vol.%WCp composite filler, the thickness of the interfacial reaction increases with increasing brazing temperature. The maximal joint strength was reached when the brazing temperature was 1173K. The thickness of the interfacial reaction descends with prolonging holding time. The joint strength decreased with prolonging holding time. When the Si₃N₄ /42CrMo were brazed with (Ag72Cu28)96Ti4+[X]vol.%WCp composite filler, the maximal bending strength of the joint was up to 320.5MPa while X is 15vol.%, which is 215.5% higher than the average strength for the the case without WCp particles addtion. With increasing the percent of WCp in the composite filler, the joint strength increased firstly, then decreased. When the Si₃N₄ /42CrMo were brazed with (Ag₇₂Cu₂₈)_100-zTi_z+15vol.%WCp composite filler. The maximal bending strength of the joint was up to 320.5MPa when Z is 4wt.%.Using finite element method (FEM) analysis software ANSYS, the effects of WCp content on the residual stress between the ceramic and steel, and the numerical simulation was also validated by experimental results. According to the results of the mechanical properties tests, the effects of WCp content on residual stress in the ceramic were similar with the resualts of the numerical simulation.