Abstract
The wetting behavior and mechanical strength of silver/copper oxide and silver/vanadium oxide braze alloys were investigated for both magnesia‐stabilized and yttria‐stabilized (Mg‐PSZ and Y‐TZP) transformation toughened zirconia substrates. The temperatures investigated were 1000–1100 °C, with oxide additions of 1–10 wt% V2O5 or CuO, and hold times of 0.9–3.6 ks. Increasing either the isothermal hold temperature or time had a distinctly negative effect on the joint strength. The maximum strengths for both braze alloys were obtained for 5 wt% oxide additions at 1050 °C with a hold time of 0.9 ks. The Mg‐PSZ/Ag‐CuO system exhibited a average fracture strength of 255 MPa (45% of the reported monolithic strength), and the Y‐TZP/Ag‐CuO system had an average fracture strength of 540 MPa (35% of the reported monolithic strength). The fracture strengths were lower for the Ag‐V2O5 braze alloys, with fracture strengths of approximately 180 MPa (30% of the monolithic strength) for Mg‐PSZ versus approximately 160 MPa (10% of the monolithic strength) for Y‐TZP. The fracture always occurred at the braze–ceramic interface. No interfacial products were observed in low magnification SEM analysis for the brazing alloys containing V2O5 additions, while there were interfacial products present for brazes prepared with CuO additions in the braze alloy.
A variation in Y‐TZP/Ag‐MexOy braze joint fracture strength with varying hold times plays an important role along with the braze chemistry and composition, the brazing temperature, and the wetting angle and the interfacial products formed.