Chris,Make your own mixture by chopping up an old leather shoe and some charcoal. Place in a metal box and get it hot and soak for a while and then tip staright into some salty water. You will get some discoloration. but it will be surface hard. No doubt others will come in with ideas. Kasenit is good if you can find some.

Chris, Kasenit has long gone but there are some other alternative compounds available form some of our usual suppliers if you dig around.

However it depends on what you want to harden, how big, how many, how thick a case to do you want/need ? If you want to go ahead and without getting into too much detail you need a suitable heat source that can sustain the temperature at 750 deg C for a lengthy period – a small furnace is best. A container to pack the work in, an old tin will work but a thicker walled one is better, you need to be able to seal the top while its "cooking"

Yes BBQ charcoal will work but better if you can get bone charcoal or as Clive suggests some leather charcoal or mix of both. Carbon penetration is generally assumed to be 3-5 thou per hour depending on the compound and temperature.

If your items are small and you go for the kasenit type compound you can use a large gas torch and a makeshift hearth, the case is thin but will offer a fair degree of wear resistance and protection from dings.

Hope this helps a little

John

For the kasenit process holding it at red hart for several minutes will do the job, the longer the better but 2 or 3 mins will usually suffice 

Edited By JohnF on 04/12/2019 20:15:59

Early American firearms such as the Sharps rifles have mottled colour patterns due to their being case hardened using bonemeal….the parts were packed in the bonemeal, leaving no air spaces, inside iron tubes and brought to red heat.

Blackgates, EKP and a number of others sell case hardening compounds. They are probably all a mixture of ground charcoal, sodium ferrocyanide and barium carbonate. Which is pretty much what Kasenit was. Quicker than pack carburizing and they produce a good case.

I have very good results with that same stuff from ebay.

I really wouldn't bother making my own!

Jim

Wikipedia has a reasonable description of the case-hardening process and mentions in passing the similar processes of nitriding and boriding amongst other similar surface treatments for low carbon steels.

John

My dad was a master weighing machine maker and repairer. Weighing machines have steel knife-edge bearings that rotate on either hardened steel or agate V-blocks. He mostly used agates.

He would use cast steel blanks and file them to the required sized knife-edge before hardening them. This was an apparently primitive process where he would hold the bearing with spring pliers, knife-edge down and horizontal, in the flame of a Bunsen burner, until it was red hot. He then dipped it in Kasenit, shovelled are little more onto the edge, and returned it to the flame to get it red hot again. This was repeated 2 or 3 times when he then plunged it into cold water and stirred it around until cold. When tested with a file it was always glass hard, and lasted many years in service.

Ron, quenching in oil (or brine or water) will only harden a metal if it has a high enough carbon content such as silver steel or gauge plate. If you did it with normal EN1A or EN3 then it would do nothing except make the part dirty.

Case hardening increases the carbon content of the metals surface which can then be hardened but it is only the surface so ideal for wear surfaces and as the core will retain the properties of the original metal it will have been easier to machine and won't be as brittle as a fully hardened item. Once you have increased the carbon content then you heat and quench as you would the higher carbon steels so oil, brine or water will all work

That’s interesting, thanks Andrew

MichaelG.

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Incidentally: It’s too many years ago for me to remember what material was used, but I recall when I worked at Kodak we had a batch of small steel levers [camera mechanisms for the use of] which failed rather dramatically at a 90° bend … it turned out that the nitride hardening had penetrated into micro-cracks in the bend and formed ‘textbook’ stress-raisers.