Foil or ATP-641 440c heat treating

[squigly1965]

I am making some knives from 440c. I have previously sent them out for heat treatment. but have decided to try my hand at it. I have a heat treat oven able to hold temp +- 2degrees F.

After some research I’ve come up with 2 possibilities.
Wrap in 309/321(not sure which) foil or coat in ATP-641.

ATP-641 Seems like it can be used but only found a couple instances of it being recommended. As it would be the cheapest option I would prefer it. I did see somewhere the Brownells antiscale product could cause pitting at temps above 1600F.

If anyone has good/bad experience with ATP-641 on 440c I would appreciate your insight

Thank you for your time
Chris

[jimmontg]

I was appointed the heat treater at a machine shop because I made knives (really, no other reason), but had only ever used O1, D2 and 440C. They had a product for coating carbon steels mostly is what I was told. Apparently the ATP-641 doesn't hold up to long high temp soak times very well. I tried it on a piece of 440C at 1900 degrees and it cracked and it didn't look very good at all on the test piece. Worked great for O1, but not stainless or even A2. I had to use it for machined parts I couldn't wrap and the results were mixed until I set our oven up to take an argon atmosphere. The machinists worried about some of their parts or we sent the parts out, but on some parts some pitting was allowed as cosmetics were not important.

Believe me, if there was a coating material that consistently worked well for stainless heat treaters would be using it instead of the foil wrap which is expensive and labor intensive.

[Bob Hatfield]

Yes the heat treat SS foil is expensive for the initial buy. It comes in a 25 foot roll and you can heat treat up to 50 knives with that roll. when you spread the cost over 50 knives, the cost is very reasonable. I use a 6 inch section for one hunting knife, or you can use a 10 inch section for two knives and be able to heat treat over 50 knives.