Wetting of AgCu-Ti filler on porous Si3N4 ceramic and brazing of the ceramic to TiAl alloy

The effect of Ti content on the wettability of AgCu-Ti filler on porous Si3N4 ceramic was studied by the sessile drop method. AgCu-2 wt% Ti filler alloy showed a minimum contact angle of 14.6° on porous Si3N4 ceramic during the isothermal wetting process. The mechanism of AgCu-Ti filler wetting on porous Si3N4 ceramic is clarified in this paper. Porous Si3N4 ceramic was brazed to TiAl alloy using AgCu-xTi (x = 0, 2 wt%, 4 wt%, 6 wt%, 8 wt%) filler alloy at 880 °C for 10 min. The effect of Ti content on the interfacial microstructure and mechanical properties of porous-Si3N4/AgCu-xTi/TiAl joints are studied. The typical interfacial microstructure of p-Si3N4/AgCu-Ti/TiAl joint is p-Si3N4/penetration layer (Ag(s,s)+Si3N4+TiN+Ti5Si3)/Ag(s,s)+Cu(s,s)+TiCu/AlCu2Ti/TiAl. The maximum shearing strength of the brazed joint was 14.17 MPa and fracture that occurred during the shearing test propagated in the porous Si3N4 ceramic substrate for the formation of the penetration layer.