Nitriding in house

Anybody here have salt bath heat treating on site?

We have an idea for wear items that includes salt bath nitriding, my partner found some process equipment and has been considering setting up a heat treat department.

Our building is actually several buildings joined together and we have a 40x100 area that could be dedicated to heat treat.

The bath we found is gas fired and has plenty of capacity for our needs it is 5x8x4 feet deep. I am aware of the toxic aspects of the salts used and we have no prior experience in these processes. Reading through past threads only touch on not doing this at home. This is an industrial facility on 2 acres in a heavy industrial site, it was actually a foundry at one point.

Please add some meaningful content to the discussion, we are not looking to do this as a hobby or on a whim, cost to operate and logistics of operation are of primary importance.

Steve

My employer has a salt bath nitride line on site. I don't know everything about it and don't claim to know a lot about the process, but can share the bits I know.

I know our line was grandfatherd in by the EPA long before I started with the company in '85 and it cannot be transfered or moved from our plant. I haven't heard of any new salt bath lines going in in the US since I started. Everyone uses gas nitride except for the few holdouts like us that can use salt bath.

I'm guessing you haven't looked into it too far because with the sianide I would never see CALy allowing it. This is some really nasty stuff.

Now as far as results go, if you perfect this it is better than gas nitride, but at a huge cost to the enviroment. I'm no greeny or anything but this results in so much nasty waste it's not worth getting into. With the wide range of alloys and very controled heat treatments avalable today nitriding isn't as necessary as it once was. We do not allow any new product to require salt bath nitriding, only gas these days.

We only nitride our own product but I was told by an outside metalirgest in the late '80s that our line was the best in the world, beating a close second in Germany. If that's the truth I would RUN not walk away from this process. We have since bought companies that have gas nitride lines and have designed our newer products to preform within the condfines of what gas nitride will offer.

Hate to rain on your parade but I'll bet you will find something much better to do with this space.

Tank

I have not looked into the regulatory aspects of a salt bath process and we had considered gas but, the bath offers advantages for our product. I know enough to understand that the vapor is deadly, I was not aware of other toxins involved or the residual waste considerations.

The absents of these on the market is a good indication they are no longer accepted. My partner has a fascination with molten salts and this was an off shoot of that interest. Could you elaborate on the gas process and how it would perform on low carbon alloys.

Steve

I don't know a lot about it either, but have had to send parts out for it due to customer specifications. It is getting less and less popular, in favor of gas nitride or ion nitride. Much cleaner processes.

Nitriding - Wikipedia, the free encyclopedia

In addition to the workplace hazards (cyanide vapors, etc) the spent bath contains cyanide and is hazardous waste.

There are cyanide-free baths now. You might contact this company which makes cyanide-free salts:

Salt Bath Nitriding - Delamin

I have worked around cyanide and am now sensitive to it, the shop I used to work in used it for stripping gold. He kept a hot plate with a beaker of the stuff cooking and the fumes would go out the fume hood but sitting there for years caused a problem. The stuff is nasty it rusts everything.

Regarding the salt chemistry we are looking at non cyanide baths, particularly the process is liquid ferritic nitrocarburizing.

This process uses cyanates not cyanide to deliver the nitrogen.

Steve

Steve in SoCal said:

The absents of these on the market is a good indication they are no longer accepted. My partner has a fascination with molten salts and this was an off shoot of that interest. Could you elaborate on the gas process and how it would perform on low carbon alloys.

Steve

Click to expand...

I'm not able to help with that. We nitride 400 series stainless and some tool steels. Also the gas line I spoke of is at a differnt plant and division and I have not been there. I did see monthly reports on the project when we were moving parts from the salt bath to the gas line and it took quite a bit of testing and tweeking of the gas process to get acceptable results on our parts. Much of these reports were over my head but I can understand the case thickness, micro cracking, ect.

We still use our salt bath process, but like you said about the avalibility of this process on the market, we needed to develope an option if something would ever happen to our line.

Now, I have a stupid question for you folks on this topic. It seems to me that even though we have a documented process and recipe for our salt bath and gas it seem like this "process" is filled with black magic and tribal knowlage. At least on our prints I don't see "nitride per MIL SPEC XXX" or any other governing body spec. on this. I don't know of these recipes to be standard processes like a precipitation hardening or something like that. I guess my question is how do you develope your process once you would have a new line?

Now before everyone jumps on me for my ignorance, I only know what goes on at our plant and I don't know much about what the rest of the world does with their nitrideing.

New Link to Delamin

mark thomas said:

In addition to the workplace hazards (cyanide vapors, etc) the spent bath contains cyanide and is hazardous waste.

There are cyanide-free baths now. You might contact this company which makes cyanide-free salts:

Salt Bath Nitriding - Delamin

Click to expand...

New link:
Delamin - Del-Gen™ Premium

If it was me I would go to the city and see if they would even issue you a permit to run an HT'ing line before I wasted any time thinking about installing a line. I would think there's a good chance their going to not allow you to install a line.