Schematic of the superalloy fixture and sample construction stage.
AutoCAD design and the actual Superfixture.
Superfixture
Diffusion bonding is a solid-state joining process that is based on the atomic diffusion of elements at the joining interface. The applied pressure plays an important role in joining the surfaces in diffusion bonding method. Therefore the pressure tools should have relaxation and creep resistance at the operating temperature which is 1000 Celsius in the NiTi bi-layer composite manufacturing.
The only available option which also has good mechanical properties among other materials was Superalloy. Therefore a fixture was designed by AutoCAD software. Superalloy nickel-based Inconel 738 was prepared by alloying using Vacuum Induction Melting (VIM) furnace. Then Inconel ingot was cut with the wire cut machine and drilled with the spark erosion drilling machine. The Nuts and bolts of the fixture also were made of the superalloy Nimonic 80A. The applying pressure to the samples was adjusted by the torque meter and following screw equation:
