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Case Hardening Experiments Mod-Up

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For this Mod-Up the goal is to come up with useful case hardening materials and methods for the hobbyist workshop. A method that uses commonly available, safe materials that produce repeatable results, in a reasonable time, is the hoped for goal. Actual experimentation, and results, rather than theoretical arguments, opinion, and hearsay (of which there seems to be a great quantity online) are the purposes of this Mod-Up.

Anyone can join, but I hope that there will be contributions results (and pics if useful) of actually testing rather than just procedural theories. And for any experimenter no matter if those ideas don't work, or do work out, either result is equally welcome!  Thank you, thank you! :bow: :bow: :beer:

Since this is a Mod-up, to put some very slight urgency to the matter, this thread will be closed, June 9, 2015.

Finally one stong caution. Some of the commonly used commercial or DIY suggested ingredients, the ferri and ferro cyanides can under certain conditions of heat or acidity produce cyanide gas, which is deadly. Online discussions disagree on what those conditions are, just as online discussions seem to disagree on most points re. case hardening. I personally intend to steer clear of them in this Mod-Up. In fact the desired result is a usable case, using commony avaiable materials that are reasonably safe.

Anyone want to join me trying out smelly concoctions and setting them on fire for the greater good? Thanks in advance if you do!  :beer:

I have seen this method used but a now passed over model engineer but not used it as we do not have a coal fire

He used to wrap the part in question in old cotton rags seal them in a tin ( small parts in a Bruno baccy tin) put them in the fire before going to bed this gave them a long hot cook in the embers , these were retrieved next day befor his boss slung them of with the ashes, he then heated them up to red heat and quenched in water .

Now I think that this method gave a shallow case but as it was for the motion work on loco,s it was ok , his reason to harden them was it gave a fine finish when polished up and a small amount of corrosion resistance

If it's not the info you want then delete this post
My self I used a kasenite but dip the part in water then into the compound then heat to red and quench, a point often missed is that a heat up to red and a slow cool will soften the case ,but reheat and quench will restore it

Stuart, not a problem, that's good info to try if someone wants to.  :beer:

I've got a similar direction I'd like to try in conjunction with charcoal making. One of the oft-stated theories is that cabon monoxide, rather than just carbon itself is the causative agent in closed vessel case hardening. Some say that pure carbon in the form of charcoal is not very effective in comparison with hooves, horns, leather scraps, etc. My guess is that these (and perhaps rags) may pyrolise to carbon, and the pyrolisis itself is important.

During wood pyrolysis, lots of carbon monoxide is evolved. So I thought I'd try putting those two things, charcoal making and hardening case together to see what happens.

One of the interesting questions to me is just how much oxygen is needed to produce the (supposedly) necessary carbon monoxide. Is an absolutely sealed container with nearly pure carbon perhaps too poor in oxygen to produce enough carbon monoxide for a case? Or is the carbon monoxide not the right transfer agent -- perhaps something other in say hooves, or rags is responsible. Anyway, trying things out is the real way to solve these kinds of puzzles.

I also would like to try Andrew's sugar suggestion.

Crushed bone and charcoal has been used also historically for case hardening, packed in an iron box and left sometimes for days, in a furnace.

I once read somewhere that they used to wrap it in leather inside a sealed metal box and then heated it to red heat.


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