Importance of thermocycling vs austenitizing in 52100?

Badlands Rifleman said:
So I’m hardening more coupons tonight and grinding them way deeper. I’m actually looking at the sparks being thrown while I’m grinding them. It goes from no sparks to lots of sparks the more I grind. The best thing is that these are all getting hard and they all were DET annealed. What a rookie mistake thinking that the clay would stop all decarb. The more I thought about what you said the more it was making sense. So far it’s looking like 1500 austenitize for 15 minutes is the hardest quench.
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At least using cryo, it seemed like i didnt hit the peak hardness until 1600. Going from an annealed state.

That said. I don't think i recommend actually using that temp, i ended up scrapping the actual blade i austenitized there. I ended up with issues. I need to rule out some things, and try again in the future.

Specifically i want to try this out with completely stock removal. The blade i did the high austenitize on was forged by hand down from some decently sized round stock. So i can't rule out issues with the forging rather than the ht.

Now that I'm thinking about this. I might make some little fixed blades with 52100, and mess with a few temps and see what happens. After I'm done with this big batch of kitchen knives I'm doing.
 
Another update. I did three coupons tonight. All three were processed using the DET anneal recommended by Larrin at the end of the above linked article. They all were coated with NuScale 2000 each time they were put in the kiln. (I’m definitely going to try the sheet metal envelope in the future) I did one at 1500, 1515, and 1530. Each had a thin layer of decarb after quenching. One way I could tell this was by trying to drill into them with an HSS drill bit on my drill press. The softer outer layer would get drilled through and then I would hit hard steel. This would create a divot about 1/8” in diameter. This softer layer was no thicker than 1/64”, if that. I’m pretty sure I can also tell this softer layer by the sparks as I ground them. I’d start with a 120 grit belt and the first second or so of grinding I wouldn’t have many sparks, then it would take off like a sparkler. Then I’d clean that up with a 220 grit belt and test it at the drill press again. This time I would have a much smaller divot, less than 1/16” in diameter. I’d also check it with my 65 hrc hardness file and it skates like a dream. Of the three coupons I can’t say for certain which is hardest, all three are very similar, but I think the 1530 is a tad harder than the other two. I’m not sure there’s enough difference between them to tell functionally though in actual use. I I think for my knives I will go with the 1515 since I’m looking for a balance of harness and toughness for the bushcraft style knives I make. I appreciate everyone’s input so far and if anyone else has more thoughts I’d love to hear them.
 
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Natlek said:
This is the fourth or fifth piece of 52100 steel that has gone through thermal cycling in the same envelope, ordinary sheet metal with a thickness of 0.4 mm . Stainless heat treatment foil would cost me more then 52100 steel cost :)

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This looks like a very good idea, thank you for sharing it.
 
One tip. Idk if i would call it 100% full proof. Is generally if i dip the blade in ferric chloride. I can see areas with decarb, and areas that are down to good steel. The decarb tends to look much lighter than the normal steel after an etch.

Also, just make sure you arent quenching the blade in the packet if you do that. Depending on what the blade is, what kind of cycling I'm doing etc. You can possibly even get away with just not grinding the blade before cycling, then do your grinding, then coat it before the austenitize and quench. And be left with not a ton of decarb (of course there will still be some).

But yeah. Foil packets (or sheet metal i suppose) > coatings Ime. Maybe i just haven't prepped well enough or something. But any high alloy steel after i put atp antiscale had a decarb, and every time I use foil, the blade comes out with no decarb at all from what I can tell. Plus when I plate quench with antiscale on it gives me other issues.
 
Badlands Rifleman said:
That’s awesome! Do you mind if I ask what your austenitizing temperature and temper were?
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I austenetize 52100 at 1525 F with a 15 minute soak. Quenched in 4 gallons of Parks 50 equivalent for a count of 10 then into chilled quench plates. The plates are clamped and then dunked into a 5 gallon bucket of ice water, then the blanks are removed and moved into kitchen freezer.

Tempered at 300F to get 63 Rc and 350F to get 61 Rc.

This was with AKS sourced steel.
 
Seedy Lot said:
I austenetize 52100 at 1525 F with a 15 minute soak. Quenched in 4 gallons of Parks 50 equivalent for a count of 10 then into chilled quench plates. The plates are clamped and then dunked into a 5 gallon bucket of ice water, then the blanks are removed and moved into kitchen freezer.

Tempered at 300F to get 63 Rc and 350F to get 61 Rc.

This was with AKS sourced steel.
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Thank you, that’s an interesting method. I’ll give it a shot when I get my quenching plates set up.
 
Blankblank said:
One tip. Idk if i would call it 100% full proof. Is generally if i dip the blade in ferric chloride. I can see areas with decarb, and areas that are down to good steel. The decarb tends to look much lighter than the normal steel after an etch.

Also, just make sure you arent quenching the blade in the packet if you do that. Depending on what the blade is, what kind of cycling I'm doing etc. You can possibly even get away with just not grinding the blade before cycling, then do your grinding, then coat it before the austenitize and quench. And be left with not a ton of decarb (of course there will still be some).

But yeah. Foil packets (or sheet metal i suppose) > coatings Ime. Maybe i just haven't prepped well enough or something. But any high alloy steel after i put atp antiscale had a decarb, and every time I use foil, the blade comes out with no decarb at all from what I can tell. Plus when I plate quench with antiscale on it gives me other issues.
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I will give the acid a try as well, I appreciate the info!
 
I did my first 52100 HT batch this past week! I used some 321 foil to make a pouch for 3 52100 blades, 1700 for 30 min, air cool. 1460 for 30, air cool. 1460, 30 min, slow cool to 1260 (DET), then air cool. When this was done, I removed from the foil pouch and applied ATP 641. Then 1525 for 15 minutes and quench. I used AAA at 110 degrees for the quench. Taking the blades from the quench after being fully cooled, they showed 66-67 on my rockwell tester with no grinding done. 350 temper in the oven 3 times for around 90 min each time shows 62 HRC on the rockwell tester. Hoping to grind and play with one of these soon! May drop them down to 60-61 hrc for hunting knife use for more toughness?

It was my first time using the foil or ATP 641 and my first time using 52100 with all of the cycling done from KSN. The ATP 641 is nice, but a pain to do for each cycle, so I was glad I used the pouch for the prep cycles and the ATP for the quenching process.
 
Taz said:
I did my first 52100 HT batch this past week! I used some 321 foil to make a pouch for 3 52100 blades, 1700 for 30 min, air cool. 1460 for 30, air cool. 1460, 30 min, slow cool to 1260 (DET), then air cool. When this was done, I removed from the foil pouch and applied ATP 641. Then 1525 for 15 minutes and quench. I used AAA at 110 degrees for the quench. Taking the blades from the quench after being fully cooled, they showed 66-67 on my rockwell tester with no grinding done. 350 temper in the oven 3 times for around 90 min each time shows 62 HRC on the rockwell tester. Hoping to grind and play with one of these soon! May drop them down to 60-61 hrc for hunting knife use for more toughness?

It was my first time using the foil or ATP 641 and my first time using 52100 with all of the cycling done from KSN. The ATP 641 is nice, but a pain to do for each cycle, so I was glad I used the pouch for the prep cycles and the ATP for the quenching process.
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62 hrc is fine for 52100.

Hoss
 
Is decarb that much of a concern? I've never used an electric furnace and I know decarb is worse in them because there's no gas to eat up the oxygen in the atmosphere, but I've always been able to grind right through any decarb I incur in the heat treating process.
 
I lost around .035"-.40" from 80crv2 from decarb on 1/8" stock recently. Basically went from 1/8 to 3/32" after grinding the decarb off. 52100 isn't as bad, but I didnt want to lose any thickness if I didnt have to. Stainless steels need to be protected due to the higher temps.
 
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