Microstructural Evolution and Mechanical Properties of ZTA Composite Ceramic/GH3536 Nickel-Based Alloy Brazed Joints

Abstract:

Reliable zirconia-toughened alumina (ZTA) composite ceramic/GH3536 nickel-based alloy brazing joints were fabricated using AgCuAlTi filler. The effects of brazing temperature and holding time on the interfacial microstructure and shear strength of the brazing joints were investigated. The typical interfacial structure of the joint brazed at 980 ℃ for 10 min is ZTA/TiO+Ti₃(Cu,Al,Ni)₃O/Ag(s,s)+Cu(s,s)/AlNi₂Ti+Ti₂Ni/Fe-Cr+Ni-Fe-Cr/GH3536. The two components of Al₂O₃ and ZrO₂ in the ceramic matrix participate in the interfacial reactions together. Ti₃Cu₃O is formed by Al₂O₃ with Ti and Cu in the liquid filler and ZrO₂ reacts with Ti and Cu to form TiO and Ti₃Cu₃O. Ti₃(Cu,Al,Ni)₃O is formed through the solid-solution of Al and Ni into Ti₃Cu₃O. With the increase in brazing temperature (940–980 ℃) and holding time (1–10 min), TiO, Ti₃(Cu,Al,Ni)₃O and AlNi₂Ti layers are thickened, and the joint brazed at 980 ℃ for 10 min has the maximum shear strength of 123 MPa. When the brazing temperature exceeds 980 ℃ or holding time is longer than 10 min, TiO on the ceramic side is converted to Ti₃(Cu,Al,Ni)₃O. Meanwhile, a large amount of generated AlNi₂Ti excessively consumes Ti in the filler, thereby hindering the generation of Ti₃(Cu,Al,Ni)₃O. So the Ti₃(Cu,Al,Ni)₃O layer is no longer continuous, which ultimately degrades the shear strength of the joint.