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This question is one being asked in many brazing shops today, and the answer is a resounding “Yes!” — carbon-fiber reinforced carbon (C/C) fixtures are being used more and more frequently in brazing shops around the world due to their lightweight, high strength, and dimensional stability over a wide temperature range as compared to similar fixtures made from steel.

As shown in Fig. 1, carbon-fibers are long filaments made of carbon, that when blended/woven in a matrix of carbon, creates a reinforced carbon structure that is very strong, lightweight, and has some flexibility. When woven into a carbon-fiber reinforced carbon structure, the material looks like that shown in Fig. 2, where the visible “weave” resulting from reinforcing carbon fibers is clearly evident. When such structures are stacked into a fixture for use in a brazing furnace, it would look similar to that shown in Fig. 3.

In my last two articles, we explored the definitions of the words “brazing”, “passivation” and “defect”. Each of these words has also been mentioned and discussed in this column in years past, but I am bringing them out again to help a new generation of brazing personnel to understand them correctly. Another word that needs to be explored once again, because of its misuse by many brazing personnel today, is the word “brittle”.

Brittle: Particularly when referring to parts that have been brazed with a nickel-based brazing filler metal (BFM), I still hear some people say that those nickel-brazed joints are “brittle” joints, and thus are probably not suitable for certain applications. Be careful! This is not true! Early in my metallurgical training (I am a graduate Metallurgical Engineer from Rensselaer Polytechnic Institute) I learned that “brittle” is not a word describing “a state of being”, but instead, is used to describe a mode of failure, as in the words: “…that joint failed in a brittle manner”.

In last month’s column we explored the definition of the word “brazing”, so that the meaning of that important term could be more fully understood and differentiated from the terms “soldering” and “welding”. In this month’s column, I would like to take a look at some additional words that are often misused in the world of brazing, namely, the words passivation and defect. These words have been mentioned and discussed in this column in years past, but it’s time to bring them out again for a new generation of brazing personnel. I still hear people use these metallurgical terms improperly when they are describing certain criteria related to braze-prep or braze-inspection; so let’s look at them again to understand them more correctly.

Passivation vs. Pickling: In a number of brazing shops I visit there still seems to be some confusion regarding the correct use of the term “passivation” (when “pickling” is actually meant) when it comes to preparing metal surfaces for brazing. The two terms, “passivation” and “pickling”, illustrated in Fig. 1, have completely opposite meanings, and thus, these two terms need to be clarified so that brazing personnel can use these two metallurgical terms correctly.

  As we start out this new year, I think it would be good to review the definition of the word “brazing”, since it is somewhat complex, and some aspects of the definition are still being misused by a number of people in the brazing industry, not only in their speech but also in their writing. So, it’s time to take a fresh look at the word, especially for those who are somewhat new to brazing, and perhaps for some older persons who never really understood what that definition meant in the first place!