52100 (Aldo's) alternate heat treat= Epic Fail !!!!!!

Willie71

Willie71

Warren J. Krywko
Joined
Feb 23, 2013
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There have been a few posts on 52100 heat treat, and many have used a series of decreasing temps from 1650f down. I thought I would give an alternate a try after discussing heat treat with Nick. I soaked the 52100 blade in my new Evenheat kiln at 1475 for 45 minutes, then quenched it in Maxim Dt48. Snap temper at 300f, and it tested at rc64. I used 1475 because of the fast oil, as per manufacturers recommendation. Medium oil works better with 1500f. While proving little, at least I know I can get it to harden without all of the thermal cycling. Previous tests with a 10 min soak were a supreme failure.

Btw, the kiln is such a step up from the forge it's unbelievable.
 
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I went from 1525F down to 1500F with a 15 min soak and got higher hardness.

52100 is a hypereutectoid steel. It can have up to .30% more carbon so you have to be able to deal with it. Part of managing it means knowing what you start with. I don't think you can avoid the "pre-heat treat" regime and truly know what you have. You have to put all those carbides into solution with a high initial heat(1625F) and let them cool quickly enough to keep them from getting bored and wandering into the grain boundaries. I would think that shooting for a majority structure of fine pearlite or small spheroids.(maybe some upper bainite, but I haven't looked into that too much) is the goal. For the final quench, I think if you went to the high end(1550F) you'd put too much back into solution... and 1475F is close to an undersoak. Seems to me that 1500F is the happy place for the average home heat treater.

I try to leave as few unknown variables as I can.
 
How's the grain looks? it sure would simplify 52100 ht if it performs well.

My cautious head - thinking out loud: given a long soak at 1475F, enough C dissolved from initial (FeCr)3C (spheriodized carbide) 14% by volume. C is a fast diffuser, where Cr need higher temperature to distribution in solution. After quench, how much spheroidized carbide (primary) remain? carbide formed&precipitated? hardness uniformity? etc?
 
Bluntcut said everything I'm not smart enough to remember... I think... :confused:

In my opinion, you are at the mercy of any previous treatments, good or bad. If you want to be sure of consistency, you need to start at the beginning(which is around 1625).
 
Just for discussion, I'm learning as I go, I noted Nick's heat treat had a 1200 or so soak prior to heat treat. Aldo's 52100 is very spheroidal anneal, which causes much of the problem we have heat treating it. From the little I know, we can accelerate the process of getting everything into solution by using higher heat, then cycling down to refine grain, or using longer soaks at lower temp. Please correct me if I'm wrong. If the steel was forged, the cycling temps would be necessary, but I did a stock removal blade here. The 1475 is lower than most recommend for 52100, but I used the manufacturer's recommendation for temp with a fast oil.

Bluntcut, I was wondering about the elements other than carbon with this method. I may have a blade that is not anything more than 1095 performance with unused alloying elements because of the heat treat.
 
So no triple quench, just a 45 minute soak at 1475? How fine is the grain after this...have you checked a broken piece yet?
 
I haven't broken a piece. I'll do that tonight. The grain "should" be fine, as the temp was too low for grain growth. there was a fair bit of decarb, a bit more than a 10 minute soak in a forge. If the steel wasn't spheroid annealed, I don't think this would have been a good option. If I understand correctly, the triple quench is to accelerate getting everything into solution, then to refine grain. It is the only option you have in a forge as decarb becomes an issue. In a kiln, longer soaks are possible. I will be doing some more Verhoeven reading today to see the effect of the 1475 on the chromium, if it simply is too low to get the chromium into solution. The amount of chromium has an effect on this, and 52100 has no where near the chromium of a stainless. In simple terms, I treated it like a higher alloy O1 to see what would happen. I am not suggesting this is the way to go, but posting an option that requires more testing to see where it leads. I tested three areas of the blade, and the hardness was exactly the same in all three areas.
 
Willie71 said:
I haven't broken a piece. I'll do that tonight. The grain "should" be fine, as the temp was too low for grain growth. there was a fair bit of decarb, a bit more than a 10 minute soak in a forge. If the steel wasn't spheroid annealed, I don't think this would have been a good option. If I understand correctly, the triple quench is to accelerate getting everything into solution, then to refine grain. It is the only option you have in a forge as decarb becomes an issue. In a kiln, longer soaks are possible. I will be doing some more Verhoeven reading today to see the effect of the 1475 on the chromium, if it simply is too low to get the chromium into solution. The amount of chromium has an effect on this, and 52100 has no where near the chromium of a stainless. In simple terms, I treated it like a higher alloy O1 to see what would happen. I am not suggesting this is the way to go, but posting an option that requires more testing to see where it leads. I tested three areas of the blade, and the hardness was exactly the same in all three areas.
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The only question I answered is that the blade fully hardened, and is evenly hard along the full length of the blade. The rest is still a question. I wish I had Kevin Cashen's equipment about now. I have a colleague with microscopes, so I might be buying one of their older ones.

I'll do an experiment tonight, three pieces from the same stock. One will be just the 1475 soak, one will be triple quench with final HT at 1500, and the other will be triple quench with 1475 heat treat. I will test right out of quench, and then after 400f temper. Maybe I'll do a piece with dry ice as well to see what happens. That will have to wait until Saturday. I will Rc test the pieces, and break them to see grain. (I thought grain was too fine for us to see with the naked eye???)
 
Why are folks doing a triple quench? You will get the same result with a triple normalize(with maybe one quench) without the added stresses

1625F - cool to magnetic
1525F - cool to magnetic
1475F - oil quench here if you want
1300-1350F - (2-3x) before drilling, working

Final quench
1300F stress relieve(optional)
1500F hold 15 mins, oil quench
 
Willie71 said:
(I thought grain was too fine for us to see with the naked eye???)
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Not always. You can tell if the grain is large because the grain will be about the size of sand, whereas a fine grain will look solid and smooth.
 
Rick Marchand said:
Why are folks doing a triple quench? You will get the same result with a triple normalize(with maybe one quench) without the added stresses

1625F - cool to magnetic
1525F - cool to magnetic
1475F - oil quench here if you want
1300-1350F - (2-3x) before drilling, working

Final quench
1300F stress relieve(optional)
1500F hold 15 mins, oil quench
Click to expand...

I refer to the cycling as triple quench. Stacy had a post on this a while back where metalurgists are split on the need for quenching or just cooling to black. I haven't quenched 52100 as I have fast oil and haven't bought commercial medium oil yet. I didn't want to ad the stress from the oil I have. I'll pick up 5 gallons of canola for this experiment and see where it leads me.

Warren
 
Carbon plays a central role in what the final structure going to be. I was wondered if there enough C aus-dissolved by your method for a C rich martensite matrix(MM). During temper, Cr alloying and cementite precip (FeC) with C from MM, which could lead to C lean MM. At the same time retained spheriodized carbide is quite large (0.5um) to support keen & stable edge. CrC & FeC are more desirable form of carbide because of small size and placement.

According to research data (yeah those with cool SEM & TEM toys), Si serves as grain nucleation & growth preventer. Other elements play their usual known role depend on micro structure at point in time.

1625F mentioned by Rick is a good/safe temperature for aust-dissolution of spheriodized carbides. However at this temp, big grain growth occurred, hence need to refine it by stair step grain nucleation (via Si, martensite, carbides, pearlite, tight spacing inter-lamellar, ...)

Regardless of forging or stock-removal, I think for good perf 52100, normalization & grain refinement are necessary, albeit time consuming.

I recently get beyond the thought/belief that high perf highly correlated to hardness. Simplifying my 52100 tinker to just molecular type/bond, inter-molecular, C accounting. I actually enjoy hand-waving metallurgy, since formality would expose my blissful ignorant on subject matter ;)

Willie71 said:
Bluntcut, I was wondering about the elements other than carbon with this method. I may have a blade that is not anything more than 1095 performance with unused alloying elements because of the heat treat.
Click to expand...
 
Willie71 said:
I refer to the cycling as triple quench. Stacy had a post on this a while back where metalurgists are split on the need for quenching or just cooling to black.
Click to expand...
I used to quench on every normalizing cycle, except the first high temperature one. I have since switched to using a magnet while normalizing. All you need the steel to do is form another structure after austenitizing. As soon as it gets back to magnetic, you're there... start you next cycle! It's about the most accurate use of a magnet that I've come across. lol.
 
Rick Marchand said:
I used to quench on every normalizing cycle, except the first high temperature one. I have since switched to using a magnet while normalizing. All you need the steel to do is form another structure after austenitizing. As soon as it gets back to magnetic, you're there... start you next cycle! It's about the most accurate use of a magnet that I've come across. lol.
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Thanks for that! Should help me this weekend.
 
IMO - based on my crude experimental data (EvenHeat oven + dry-ice and then LN2 later on) - i.e. ymmv

Pearlite (no quench) vs Martensite (quench).

Obviously both will refine grain but the question is 1. how fine? 2. Si and Cr distribution (ultimately CrC)?

P grain nucleation via pearlite structure + Cr & Si. Hopefully uniformly distribute non-Fe between P structure getting smaller as temp decreased. Then lock in place by final hardening M structure.

M grain nucleation via Martensite + Cr + CrC + Si. Cr & Si are isolated by M structures. I internalize this as honey-comb divide and divide, possibly avoid large Cr & Si aggregation. When ht completed, ideally we want CrC be well distributed and as small as possible.

Willie71 said:
I refer to the cycling as triple quench. Stacy had a post on this a while back where metalurgists are split on the need for quenching or just cooling to black. I haven't quenched 52100 as I have fast oil and haven't bought commercial medium oil yet. I didn't want to ad the stress from the oil I have. I'll pick up 5 gallons of canola for this experiment and see where it leads me.

Warren
Click to expand...
 
I've received 52100 from different vendors lately, all of it is spheroidized. At least the stuff I've gotten. My understanding, as was mentioned, in order to get the carbides into solution, you have to perform the grain cycling steps (at least the first high heat), and the higher initial heat of 1650 or so is very critical. Of course, this causes grain growth, especially if left to soak for a while, so we grain cycle a few more times to reduce the grain size (introduce more nucleation boundaries). I believe this initial high heat puts all of the carbides into solution, so we can utilize a lower temp (1475 vs 1500 or 1525) to reduce RA. Most of what I have read concerning 52100 has been from Kevin, and 1475 with a good soak has been giving superb results, provided the steel is set up properly prior to hardening. Funny, I just HT a 52100 blade (copy of a Kephart Classic) last night. 1650F, 10 minutes soak, cool to black, quench. 1500F, cool to black, quench. 1400F cool to black, quench. (scale removed every cycle). 1475 for 15 minutes, quench in 120F canola oil. Temper 1.5 hours at 350. Clean scale off to bare steel again. 1.5 hours at 400. I would LOVE to have a hardness tester. There was a decent amount of decarb. I left the edge about .025, and sanding off the decarb has left an super hard edge about .005.

It would be really interesting to see tests done on triple quenching during grain cycling vs air cooling. As far as real world application, I don't think anyone would be able to tell the difference without microscopes and what have you. If the line is that fine, I tend to go with only air cooling in between thermal cycles, to reduce any chances of micro cracks that might happen during quenching, especially quenching from 1650.
 
bluntcut said:
IMO - based on my crude experimental data (EvenHeat oven + dry-ice and then LN2 later on) - i.e. ymmv

Pearlite (no quench) vs Martensite (quench).

Obviously both will refine grain but the question is 1. how fine? 2. Si and Cr distribution (ultimately CrC)?

P grain nucleation via pearlite structure + Cr & Si. Hopefully uniformly distribute non-Fe between P structure getting smaller as temp decreased. Then lock in place by final hardening M structure.

M grain nucleation via Martensite + Cr + CrC + Si. Cr & Si are isolated by M structures. I internalize this as honey-comb divide and divide, possibly avoid large Cr & Si aggregation. When ht completed, ideally we want CrC be well distributed and as small as possible.
Click to expand...

I'm guessing this debate would require tools that measure beyond a user's perceptual abilities to discern differences. While I am rarely one to suggest "good enough" is good enough, at a certain point are we improving performance, or just messing with variables that don't impact performance? (I'm wondering out loud, I don't know) What I mean is, will the difference be noted on a skinner sharpened to 1200x, or a kitchen knife at 8000x? Do we need to go to 20,000x to find the difference?
 
samuraistuart said:
I've received 52100 from different vendors lately, all of it is spheroidized. At least the stuff I've gotten. My understanding, as was mentioned, in order to get the carbides into solution, you have to perform the grain cycling steps (at least the first high heat), and the higher initial heat of 1650 or so is very critical. Of course, this causes grain growth, especially if left to soak for a while, so we grain cycle a few more times to reduce the grain size (introduce more nucleation boundaries). I believe this initial high heat puts all of the carbides into solution, so we can utilize a lower temp (1475 vs 1500 or 1525) to reduce RA. Most of what I have read concerning 52100 has been from Kevin, and 1475 with a good soak has been giving superb results, provided the steel is set up properly prior to hardening. Funny, I just HT a 52100 blade (copy of a Kephart Classic) last night. 1650F, 10 minutes soak, cool to black, quench. 1500F, cool to black, quench. 1400F cool to black, quench. (scale removed every cycle). 1475 for 15 minutes, quench in 120F canola oil. Temper 1.5 hours at 350. Clean scale off to bare steel again. 1.5 hours at 400. I would LOVE to have a hardness tester. There was a decent amount of decarb. I left the edge about .025, and sanding off the decarb has left an super hard edge about .005.
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I am not disagreeing with this method at all. I know it works, and you should be around Rc 60 based on my previous results. The think that got me thinking about this was when Nick asked me why I was cycling when I was already spheroidized? If I remember what he was getting at is the end result of his heat treat prior to quench is a spheroid structure, then the austentize and quench. From what I have learned, Aldo's 52100 is something like 99% spheroidized, where others are in a 80-90% state. This is why the cycling, but soaking long enough should get everything into solution as well (???????.- the point of my experiment. I am not trying to convince anyone this is the way to do it, but I am exploring an alternate path that MAY work.) I may have misunderstood completely, but that is what I took from the discussion. There are a lot of alloys in 52100, and they take some time to dissolve, or we can normalize (1625f) and go from there.
 
You're right, perception + bias + geometry can skew what performance mean.

My performance test is straight forward: Clean dry facial stubble shave -> 2-5 minutes whittle dry pine or seasoned oak -> 2-5 minutes of various cardboard. Great perf, if it still shaves hair and cleanly slice newsprint. Basically I seek fine-grain and a well balanced strength; toughness and wear resistance. Perf diff should be easily detected from all grit (ok, say 120 & higher). Also I usually side-to-side test my 52100 with knives with steel: cpm-m4, k390, s30v, s90v, 20cv/m390, cpm154 - all these knives were either commercial or used ht params recommended by mfg/vendor. At time, I get quite discourage chasing k390 perf :(

Willie71 said:
I'm guessing this debate would require tools that measure beyond a user's perceptual abilities to discern differences. While I am rarely one to suggest "good enough" is good enough, at a certain point are we improving performance, or just messing with variables that don't impact performance? (I'm wondering out loud, I don't know) What I mean is, will the difference be noted on a skinner sharpened to 1200x, or a kitchen knife at 8000x? Do we need to go to 20,000x to find the difference?
Click to expand...
 
Epic Fail!!!!! I tempered a second time at 400fr, and the blade came out at Rc50! I'm going to redo it tomorrow with the thermal cycling that has been the standard. Thanx for the discussion.

:grumpy: :grumpy: :thumbdn: :foot: :jerkit: :confused: :p
 
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