Let’s finish the discussion we started last time. As shown in Table 1, it is important that you look at the surfaces that you want to braze together and decide if they meet the design criteria needed for brazing.

  • If the mating surfaces to be joined are to be butted up against each other for brazing, such as that shown at the top of Fig. 1, then those mating surfaces must be very flat, with square (non-chamfered) edges and parallel to each other. This creates a good, tight joint space between them, irrespective of whether the mating surfaces are narrow or wide.
  • Proper clearance. At brazing temp there should be about a 0.001-0.002 inch (0.025-0.05 mm) gap clearance for the molten brazing filler metal (BFM) to flow through. This BFM can be provided as a brazing paste (placed on the outside of the joint) or as a brazing foil placed inside the joint.
  • Fixturing. Be sure the two 3D-printed parts are held in proper alignment for the brazing process (e.g., in a vacuum furnace or in a vacuum-sealed bell-jar for induction brazing, etc.). Proper alignment can be achieved by the use of Inconel clips, ball-tacking or perhaps by light tack welding using a small hand-held capacitive-discharge resistance spot welder. Additionally, alignment might be achieved using some lightweight carbon-fiber reinforced carbon (C/C) fixturing.
  • Brazing process. Any brazing process acceptable to nickel-based superalloys can be used for this process (as just mentioned), such as furnace or induction.

Conclusions

The world of 3D printing is growing, and brazing can grow along with it. Brazing is an excellent joining process for 3D-printed parts. It can be an important part of the process for your 3D-printed parts until you are able to make larger 3D-printed assemblies that eliminate the need for joining subassembly parts together.