Dan Kay's blog series about tight joint clearances for nickel brazing continues with part 3.

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.  

This concludes our step-by-step discussion that we began last time.

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?

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.  

Dan Kay's blog series on eliminating "holds" in brazing cycles continues.

Dan Kay's blog series on eliminating "holds" in brazing cycles continues.

I recently asked the production manager at an aerospace company, “Why do your brazing personnel have those temperature holds in their furnace brazing cycles?”

As shown in the last line of Table 2, the water that you use in your cleaning operations is very important.  I strongly recommend that you use deionized water in your shop and not well water or city water. City water can go bad on occasion, whereas having your own water deionizer in your shop is an excellent safety measure. Well water may be great for drinking, but it contains minerals (calcium oxide, magnesium oxides, etc.) that are strong braze-inhibitors.