Preventing Decarb during HT?

billyO

billyO

Well-Known Member
Hello all. I hope everyone is still staying safe and healthy.
I was about to order some ATP-641 to help prevent/minimize decarb during HT so that I don't have to sand as much of my pattern welded steel away after HT, and came across a few mentions of using Blaster(TM) graphite dry lubricant that does the same thing.
Does anyone have any info on if this true? (It would save time and shipping $ if so.)
 
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I just came across this thread and it seems like this is the answer...

Graphite spray...

Anyone here ever tried graphite spray on high carbon blades prior to heat treating to prevent decarb-scaling ? I've been reading a little bit about it and might try it.
knifedogs.com
Moderators, feel free to delete this thread. Sorry about that.
 
BillyO, if you do try the graphite spray be sure to post a follow up with your comments on graphite use for anti scale.
 
KenH said:
BillyO, if you do try the graphite spray be sure to post a follow up with your comments on graphite use for anti scale.
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Hi Ken. From the above link I posted, it looks like Steve Miller (@bladegrinder) already did the experiment and found that while effective for anti-scale use, it did not prevent the decarb.
 
I have mentioned on a couple of posts that the ATP-641 does prevent decarb. I've done a couple of knives now and went straight to hand sanding on everything but the bevels.
 
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As an update, earlier this week I heat treated 2 knives using the ATP-641 and it looks like it works to prevent decarb during the quench. I've only worked on one, but was able to go straight to 220 grit hand sanding out of the temper and the only decarb I noticed was on a small spot where the coating popped off during the quench.
Thanks for the help and info, all.
Onward...
 
The stuff I have applies like paint. Not too thick, but also I wouldn't call it thin. It took quite a bit of stirring and shaking to get it well mixed intitially, I think you can thin it down with water if necessary. The instructions (I think that's where I read this) suggest using an airbrush for a thin, uniform coat, so I guess that means you can thin it quite a bit.
Dry time was about 20 minutes when I applied it using a soft paintbrush (IIRC) but the directions say you can preheat the blade to 200 before applying. I'm guessing that not only will that speed up dry time, but also perhaps allow a thinner coating?
One thing I could perhaps save others from doing. I'm in the habit of doing one final stress relieving/thermal cycle (~1200F) after grinding and before doing the final quench. I painted the blades before this, and a lot of the clay flaked the blades after the 1200F cycle, so had to clean them and re-paint before quenching.
But, now that I type this, I'm wondering if this is going to have to be SOP, because if I don't coat them before the final 1200F cycle, I'll get some decarb and scale, won't I?
 
I wouldn't expect much scaling or decarb at 1200F.

I'm pondering, however, if foil might be the way to go for normalizing and thermal cycling. Though my goal is a little different than yours, the issue is similar when I do 52100, for example. The decarb isn't so bad at 1475-1500 austenitizing, but the 3 cycles before that, especially normalizing, really make it cruddy. So I've been pondering in investing in foil to do the first 3 cycles, then just the one HT and quench isn't so bad to deal with. Perhaps a similar process would benefit you, but adding the ATP-641 before your final heat and quench?
 
Thanks for the idea, tkroenlein. I've actually thought about using foil, but not sure if I want to add that extra step (and cost) to my process yet. Definitely filing that away for future reference, but want to play around with just the ATP-641 for a few blades first.
 
Just as an update to this thread. I've done a couple of knives now where I have still gotten a very thin layer of decarb on the knife while using the anti-scale. You literally can tell from the appearance after quenching. I still think it's thin enough that you can hand sand it away. I'm only putting on one layer of the anti-scale, so maybe I need to add another coat.
 
I worked with 01 for over 10/12 years, and used the ATP 641. I took my blades to finished dimensions ready to give an edge to. I stress relieved at 1200° for an hour with no coating, then I single coated the day before HT and added a second coat the following day that I dried with a hair drier. I would then add a third layer on the edge and about 1/8" up from the edge of the blade. I soaked at 1475° for 20 minutes in an Evenheat oven. I would run 3 at a time, so the last 2 got more than 20 minutes. The ATP always held up if I was careful to be sure there were no bare spots in the coating. If ever I found decarb at the edge, it was so shallow as to be of no concern. I did find that with 01, I could file check as soon as it cooled to hand handling heat and the file might make a very, very slight bite, but could retest 20 minutes later and the file would fully skate. I also found early on, you can hand straighten minor warpage in 01 for as long as 10 minutes out of quench. That works for 01, not so much with 10xx types.
 
Casey Brown said:
Just as an update to this thread. I've done a couple of knives now where I have still gotten a very thin layer of decarb on the knife while using the anti-scale. You literally can tell from the appearance after quenching. I still think it's thin enough that you can hand sand it away. I'm only putting on one layer of the anti-scale, so maybe I need to add another coat.
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01 and A2 steel. I do one coat, let dry over night, then another coat, dry with hair dryer, then a third coat along the edge, which is .010/.015, dried with hairdryer. Then do the HT. I get no detectable decarb unless I miss a spot.
 
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