| Vacuum Brazing of 3YSZ and CP-Ti using Ag-Cu-Pd Filler
Alloy: Interfacial Microstructure, Phase Evolution and
Hermeticity |
Abhishek Upadhyay,a, b Sandeep Kumar,a Anubhaw Kumar Singh,a Pal Dinesh Kumara and Neha Sardanab,*
Pages : 257-264
DOI:10.1080/0371750X.2026.2712333 |
| Abstract |
| Reliable and hermetic joining of ceramics to metals remains challenging due to
interfacial incompatibility and thermo-mechanical mismatch effects. In this study, yttria-
stabilized zirconia (3YSZ) was brazed to commercially pure (CP) titanium (Grade 2)
using a nominally non-active Ag-Cu-Pd filler alloy (Palcusil), under high-vacuum
conditions (~10–5/ mbar). The joint interface was systematically examined to determine
the role of interfacial reactions in achieving effective bonding without active brazing
elements. Scanning electron microscopy revealed a continuous, defect-free interface,
while energy-dispersive spectroscopy confirmed redistribution of constituent elements
across the joint. X-ray diffraction identified the formation of Ti3O, Ti2Y2O7
, Cu2TiO3
,
Cu3Ti2
, Pd3.5O4
, along with Ag-rich and Cu-rich solid solutions, highlighting controlled
phase evolution. Microhardness profiling showed the lowest hardness within the filler
region relative to both parent materials, suggesting a compliant interlayer that may
assist in accommodating processing-induced mismatch strains. Helium leak testing
showed hermetic integrity with leak rates of the order of 10–9 mbar.l.s–
1, demonstrating
suitability of the joints for vacuum-tight applications. The results demonstrate that
the controlled interfacial phase formation enables the fabrication of hermetic 3YSZ-Ti
joints using an active-element-free brazing alloy. |
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