Decarb….

[jarhead jim]

Hey all, making Damascus knives using 1084 and 15n20. Using ATP 641 I believe and swear I get more Decarb using it than not….. Do the 1600, 1450, 1250 normalize and 1475 hardening with a coat of this crap on the blade. Stays on till after the hardening sequence where it comes off at the quench. Temper for two sets at 375 with no coating on the blades as they say Decarb isn’t likely at that low heat. What gives? Is there a better gunk to put on the blades to keep it from Decarbing? I’m doing the heat treat in an Even Heat kiln and the tempering in a toaster oven. Surface grind the blades to 120 and do a preheat treat bevel.

 

[Karl B. Andersen]

How are you determining decarb? (Don't confuse that with forging scale/iron oxide)
And..........you have an Evenheat, but you're tempering in a toaster oven??

 

[Nate’s Knives]

Also I would grind to a higher grit before heat treat. The lower the grit, the harder to clean up post heat treat. At least 220-320

 

[Ken H>]

I will normally do the normalizing steps before grinding for HT, then apply the anti-scale to HT at 1475°F. If the anti-scale is still coating the blade after HT, but falling off during quench there shouldn't be much decarb on blade.

I've never used ATP 641 but have used borax to coat the blade, and for the last while I've used "Blaster Graphite Dry Lubricant", just do a search on that and several sources around $8 will show up. Grind blade to around 400 grit, spray a couple of light coats allowing to dry a few minutes between coats and it works pretty good.

 

[SBuzek]

I use a thin coat of satinite on all my carbon steel blades and get very little to no decarb.

 

[Stuart Davenport Knives]

I use ATP-641 and there is never a decarb layer. Maybe 0.001", if that. Also, I always will grind a little bit into the edge post heat treat to make sure there is no decarb where it actually matters.....where the edge apex will be.

 

[Taz]

I use a foil pouch for the normalizing and DET anneal/Thermocycles, then ATP641 for the quench itself. I didn't think ATP641 would last through all of the cycles? Or are you coating with ATP641 at each cycle? It can come off as it cools, so if you are air cooling between the cycles, it may be loosening from the blade and not protecting as much?

 

[Jesse Latham]

I use a foil pouch for the normalizing and DET anneal/Thermocycles, then ATP641 for the quench itself. I didn't think ATP641 would last through all of the cycles? Or are you coating with ATP641 at each cycle? It can come off as it cools, so if you are air cooling between the cycles, it may be loosening from the blade and not protecting as much?

I do this also.

 

[Stuart Davenport Knives]

Same. ATP-641 ony for the quench cycle.

 

[jarhead jim]

How are you determining decarb? (Don't confuse that with forging scale/iron oxide)
And..........you have an Evenheat, but you're tempering in a toaster oven??

My Evenheat doesn’t go down to 375 so I use a toaster oven with a thermocouple and digital readout for the temperature cycle. I should say I’ve never tried the Evenheat to temper because the guy at Evenheat told me it wouldn’t hold that low of heat. LB22.5. Am I wrong?

 

[jarhead jim]

I use a foil pouch for the normalizing and DET anneal/Thermocycles, then ATP641 for the quench itself. I didn't think ATP641 would last through all of the cycles? Or are you coating with ATP641 at each cycle? It can come off as it cools, so if you are air cooling between the cycles, it may be loosening from the blade and not protecting as much?

The ATP stays on my blades through the normalizing steps just fine, even after stamping my name on the blade for the most part. After the hardening it all comes off.

 

[jarhead jim]

I use ATP-641 and there is never a decarb layer. Maybe 0.001", if that. Also, I always will grind a little bit into the edge post heat treat to make sure there is no decarb where it actually matters.....where the edge apex will be.

I never get Decarb on the edge or bevel, just the flat part of the blade.

 

[Seedy Lot]

I never get Decarb on the edge or bevel, just the flat part of the blade.

If you have decarb on the flats than you have decarb on the edge. Decarb is just not going to happen in one spot, that is like saying heat in room only leaves through the ceiling.

Check out this article...

Coatings vs Foil - Heat Treating Steel - Knife Steel Nerds

What are scale and decarb and why do you need to avoid them? Are heat treat coatings or foil better for protecting the surface?

knifesteelnerds.com

And I have tested the graphite spray and it did zero for me to limit decarb, just another maker's lore in my experience.

 

[Hella Bread]

My Evenheat doesn’t go down to 375 so I use a toaster oven with a thermocouple and digital readout for the temperature cycle. I should say I’ve never tried the Evenheat to temper because the guy at Evenheat told me it wouldn’t hold that low of heat. LB22.5. Am I wrong?

The main question that hasn’t been answered yet is how are you determining decarb and if you’re possibly confusing it with scale. Decarb layer is hard/almost impossible to see with your eye unless you etch after the scale is removed and other than that can be revealed after hardening if a file or something hard bites into it.

Scale = dark iron oxide layer coating the steel, can come off in flakes

Decarb = surface layer of steel that has lost carbon and will stay soft, still looks like normal steel unless etched

You can have steel that has seemingly rough scale (whether it’s actually scale or just the burnt remains of the coating or a mix i’m not 100% sure) and no decarb, and the opposite can also be true of steel with no scale but still has a tiny bit of decarb

 

[ScarFoot]

If you’re not re-coating I suspect the 641 might be “on there” but has essentially lost its integrity. When I use it for normalizing cycles it always flakes off while air cooling. Yours might be developing cracks while it’s hot and letting air get to the blade. I’ve never had any trouble with it when I use it other than on 1095 and W2. I’ve had hardening issues using it on those two steels.

 

[jarhead jim]

The main question that hasn’t been answered yet is how are you determining decarb and if you’re possibly confusing it with scale. Decarb layer is hard/almost impossible to see with your eye unless you etch after the scale is removed and other than that can be revealed after hardening if a file or something hard bites into it.

Scale = dark iron oxide layer coating the steel, can come off in flakes

Decarb = surface layer of steel that has lost carbon and will stay soft, still looks like normal steel unless etched

You can have steel that has seemingly rough scale (whether it’s actually scale or just the burnt remains of the coating or a mix i’m not 100% sure) and no decarb, and the opposite can also be true of steel with no scale but still has a tiny bit of decarb

It’s Decarb, not scale. It has a hazy finish in certain areas. I can see it when I’m hand sanding and really see it when etching the blade.