Notice in Table 2 that there are strict requirements for the amount of oversized and undersized powder particles in each mesh size group. For example, to be classified as a -140C powder (“C” stands for “course”), the screened powder can only have a maximum of 20% -325 mesh powder. Thus, 80% of powder classified as -140C-mesh must be -140 mesh/+325 mesh, meaning it should all go through the 140-mesh screen, but 80% or more must sit on top of, and not go through, a 325-mesh screen.
Figure 3 shows a laboratory wire-mesh sieve screen used for 140-mesh powder. If atomized powder is not able to go through this screen because the openings in the screen are smaller than the size of those powder particles, then those large particles will remain on top of the 140-mesh screen and would be called “plus (+)” sized powders because they sit on top of the screen and cannot go through. Powder particles that can go through the screen are given a “minus (-)” particle-size designation, indicating that they can go through that screen.
A common way to create brazing filler metal (BFM) powder is by melting the raw metallic ingredients for the BFM in a large melting pot using induction heating and then pouring that alloyed liquid metal through a specialized atomization nozzle.
Unfortunately, as mentioned earlier, all of these temperature-lowering, eutectic-forming elements in nickel-based BFMs are also hardeners; that is, the phase structures resulting from solidification of these elements have virtually zero ductility. Thus, the last phases to solidify (in the center of the joint) will be hard and non-ductile.
Nickel brazing is unique in the brazing world in that each of the nickel-based brazing filler metals (BFMs) available for use today depends on the use of temperature-lowering ingredients (i.e., temperature-depressants) such as boron, phosphorus and/or silicon to enable the BFM’s usefulness for joining stainless steels and many other superalloys for critical aerospace applications.
Question: What is a good method to attach a large sheet of honeycomb material around the entire outside diameter (OD) of a large 304L stainless steel cylinder so that it can be effectively brazed in place around that OD?