The second precaution necessary when brazing aluminum to stainless is...

We want to use our vacuum furnace to braze a 6061 aluminum part to a 400-series stainless steel but are concerned about whether that can be done in our furnace, which only is used for aluminum brazing.

Please note, first of all, that the aluminum-oxide layer on the surface of the aluminum is very thin – only about 40-angstroms thick! That’s VERY thin, since an angstrom is only about one ten-billionth of a meter thick.

Aluminum brazing is a growing industry around the world today, and I teach a lot about this topic in each of my brazing training seminars.

SECO/WARWICK delivered and commissioned what it says is the first-ever vacuum-purging semi-continuous controlled-atmosphere brazing (CAB) furnace for a North American automotive aftermarket manufacturer. It is the company’s first furnace of any type and also its largest capital equipment investment. The furnace, equipped with vacuum purging in the loading and unloading chamber, allows for reduction of nitrogen consumption and cost. It also provides exceptional control of brazing atmosphere quality, which applies particularly to heat exchangers with joints brazed in a closed space. Vacuum purging allows for the removal of oxygen from these spaces before brazing, which cannot be achieved by traditional purging.

Atmosphere thermal processing improves the properties of fabricated metals. Operations include annealing, brazing, sintering (for powdered metals, metal injection molding and additive manufacturing) and glass or ceramic-to-metal sealing.

My recommendation is that you institute some QC tests on the plated parts that you receive back from your plater in order to evaluate the quality of that plating. The so-called “blister test” was the most important and valuable one we developed, and it should NEVER be done by the plating company but by YOU.

We plated the mating surfaces of our Inconel 738 components that were going to be nickel brazed, and the parts failed in service prematurely. An analysis showed that our brazing was OK, but the plating had peeled from the base metal causing the premature failure. How can we prevent this in the future?

People occasionally ask me for information about how to determine the strength of their brazed assemblies, which involve different types of base metals and different kinds of brazing filler metals (BFMs).

Vacuum aluminum brazing is a careful balance of time, temperature and vacuum level.