case hardening, fresh charcoal vs. re-used charcoal

[taterbug]

Wanted to break this out to a separate new topic.

Just wondering how many have re-used charcoal for case hardening, and if anyone has noticed any differences compared to fresh charcoal?  Whether the differences were in color or hardening properties.

Also, any ideas for why there may be a differences?  I have a couple of ideas, but my high school chemistry from 50 years ago is failing me, and I'm too lazy to research it on the interwebs.

And besides, google-fu descriptions of the process wont include any nice pics of ML parts

[rich pierce]

Hoping to not derail. Do you use the bone charcoal because it helps carbon penetration or gives better colors or both?

[JPK]

I haven’t found the colors or hardness to be different with used charcoal. I only reuse it once on projects that are less critical. An import ( paying job) always gets fresh charcoal. The bone and wood charcoal releases carbon monoxide and carbon dioxide respectively and those that have better understanding of what they each contribute are not getting any arguments from me. I have noticed that more wood charcoal in the mix produces more blue and water quench temperature changes the color with the same mix. This is a piece done in the 4 wood to one bone but quenched in 90 degree water. In 50 degree water more blues and mottled colors would be expected.
AA0149F3-4E50-45BB-8CAC-B4D4D9909E96 by Oliver Sudden, on Flickr

[Carl Young]

Check this thread from Rolf on his case hardening. He saved the charcoal, but I am not sure he has tried reusing it yet.
https://americanlongrifles.org/forum/index.php?topic=79931.0;topicseen

I have reused charcoal for hardening and it seemed OK. I just tested for hardness with a new sharp file, but not depth of case. Good luck and keep it up.
Carl

[Rwnblack]

I have reused charcoal but have had troubles getting the charcoal completely dry.  I think if I lived in a hotter place, I could put the charcoal in the hot sun for a few weeks.  I have dried it in a gas bbq but it takes too much gas.  I have dried some in my muffle furnace and that seemed to work.  Lately I have been using fresh charcoal (2:1 ratio of wood to bone) and that seems to be more consistent for me.

I think this was used charcoal.


This one was fresh charcoal.






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