Pressureless Bonding of 3Y-TZP and Fe Using Ti Sheet

The pressureless bonding of 3Y-TZP and Fe using Ti sheets (thickness: 0.5mm, 0.02mm) and a bonding agent has been studied. A specimen consisting of 3Y-TZP and Fe between which an agent and Ti sheet is inserted is heat-treated at 900°-1100°C for a considerable length of time in an Ar stream. To reduce the residual stress upon the interface which is caused from the thermal expansion coefficient difference between 3Y-TZP (α=8.8×10-6/°C) and Fe (α=13×10-6/°C), the optimum Ti sheet thickness has been found to be 0.5mm. When bonding is made employing a 0.5mm-thick Ti, the bonding tensile strength of 20°C/min in Ar has become more than 140MPa. The mean bonding strength of the specimens has been 50MPa with the use of a 0.5mm-thick Ti sheet under quite the same conditions. The structure of the well bonded interface has been found to be as shown below. 3Y-TZP/Titanium oxides layer (TiO, Ti2O)/Ti-rich layer (Ti with scanty Cu)/Cu-Ti alloy layer (CuTi2)/diffusion layer (CuTi2 containing Fe)/Fe(α-Fe). Utilizing the same method, bonding of 3Y-TZP with Nb, Ta (purity: 99.9%) and SUS 304 has been carried out by the heat-treatment. With the 0.5mm-thick Ti sheet, the bonding strength of TZP and Nb/Ta specimen has become more than 105MPa and 120MPa, respectively. However, the bonding strength of the 3Y-TZP and the SUS 304 has been found to be just approximately 30MPa. Such bonding strength is expected to be furthermore increased in parallel with the raise of the heating rate (20°C/min).