Cryogenic(sp) treatment

You are making mountains out of mole hills . " transformed with cold working during use of the blade" I'd like you to demonstrate that one. Maybe you ought to make knives out of Hadfield steels.
 
I would like to see it demonstrated as well, or even just more precise explanations given. The problem of conversion of retained austenite is frequently mentioned as well as it being enhanced by stressing the steel, however I have yet to see time frames for either.

-Cliff
 
The papers at the ASM conference are available but as archived.
I'll see when the exact date was so they can be referenced.

The Eta carbide debate comes from the lack of conclusion as to what actually helps the steels, getting rid of retained austenite or precipating extremely small volumes of carbide that are so small you need an electron microscope to find them.
 
Cliff,

Thanks. That Mr. Wilson and that Mr. Johnson seem like people who make blades I want. Now if others can reproduce >61 Rc cryo-quenching S30V, that'd be a lot more fun, still.
 
Can someone provide a reference to or explanation of "dimensional stabilization" and what is going on during cryogenic quenching that would improve same?

I've seen it referenced in a couple of posts and don't have a clue.
 
Originally posted by Ed Severson
The Eta carbide debate comes from the lack of conclusion as to what actually helps the steels, getting rid of retained austenite or precipating extremely small volumes of carbide that are so small you need an electron microscope to find them.
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This kinda gets to the nub of the issue... research is necessary and useful, but ultimately we must get the researchers to translate their findings into useable, actionable information and then on and into products with noticeable performance improvements.

Reminds me of the way I feel when I hear Ed Fowler saying they've pushed 52100 to new limits ... "perhaps doubling again the performance". Ok, in what measureable way? Finer grain microstructure is a good indicator, but what does that translate into for the user? And compared to what?

* Improved abrasion resistance and ergo edge retention at a given hardness? (maybe, but I'd guess not, in absence of data)
* Improved ease of sharpening? (dubious value)
* Improved toughness? (maybe... how much exactly, and in terms I can understand like Charpy or other repeatable test. Toughness improved enough so 52100 can be run harder to improve strength and edge retention (resistance to edge rolling)?

Anyway... hopefully Ed will follow up at some point.
 
There are 2 interesitng points I came away with in regards to this thread: first, that as always, Cliff will *never* admit that he's wrong, even in the face of irrefutable evidence. Second, just why does he have such a stiffy for cryo treating? Could it be that this is a new bit of the tempering process for Busse knives, Cliff's one true love? I seem to remember a while back reading that the Swamp Rat knives were cryo treated. I have no idea if this is the case with Busses, as I try to stay far away from Busse-mania. But if Busse *does* use cryo as part of their tempering process, it sure would exlain why Cliff is so high on the stuff, despite being proven wrong about its supposed benefits. After all, don't use logic or facts to try to dissuade a Bussephile; it just won't sink in.
 
Gaben, some of the points brought up on this forum are absolutely meaningless when it comes to knives ,for example eta carbides and dimensional stability. If I am making precision tooling I am interested in dimensional changes in heat treating and use. It would be nice to be able to grind a die before heat treating and not have changes due to HT. Something like A 10 will do this, most will change and even change a different amount depending on rolling direction. Retained austenite in the HT piece can in time change to martensite which will change dimensions .This problem can be minimized by reducing or stabilizing the retained austenite. BTW, comments on retained austenite on the forum - I would like to say again that retained austenite is not all bad sometimes it is beneficial.
 
Originally posted by V Shrake
But if Busse *does* use cryo as part of their tempering process, it sure would exlain why Cliff is so high on the stuff, despite being proven wrong about its supposed benefits.
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You have over-generalized. Only some of the supposed benefits of cryo, from literature, are in question. And the benefits must be kept in context of usage (e.g. precision tooling vs. improving knife blades).

Numerous reputable people use Cryo, and not just for marketing. It has it's place, depending on heat treat method and the material in question.

Two prominent examples kinda illustrate:

1. Dozier does good work with D2, and doesn't find his heat treat method benefits much from cryo, per earlier in this thread).

2. However, it's well known that, for example, Paul Bos does use cryo. To point, here's a thread where Paul Bos indicates part of his method. And of course, like any good practicioner, Bos says
Cryo. has been around for many years, But there is still alot to learn about it. Keep on testing and good luck. Paul.
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http://www.bladeforums.com/forums/showthread.php?s=&threadid=247951&highlight=paul+bos+cryogenic

Somehow, I don't think Paul Bos would do cryo if he didn't think his particular heat treat methodology/approach benefitted from the process... it's expensive and time consuming.
 
V Shrake :

if Busse *does* use cryo as part of their tempering process ...
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They do, as do many other makers and heat treaters, even Cold Steel is doing it for example. This isn't part of any arguement I have used however, which is based on the published articles, ASM and other journals which were referenced in the above. These cite multiple benefits to cryogenics and specifically deep cryo (liquid N2) as opposed to shallow (dry ice).

Ed :

The Eta carbide debate comes from the lack of conclusion as to what actually helps the steels, getting rid of retained austenite or precipating extremely small volumes of carbide
Click to expand...

So you accept the fact that the gains promoted to increasing the wear resistance by cryo are true, but would argue that it isn't because of eta-carbide formation. How can an increase of 500% in wear resistance be explained by a 10-20% transformation of retained austenite? Doesn't carbide content swamp out the martensite matrix influence on wear resistance? Or would you argue that the increase in wear resistance is not as large as presented in the ASM and other works?

As for small carbides, and a volume correlation, most of the high alloy carbides precipitated in secondary hardening are very small, nm in size, compared to 10-20 microns for the large segregated Cr carbides (a thousand times larger), however the very small ones like V4C3 can still dominate wear resistance, crucible even lists this in the "orange book".

What about the effect of the nature of the crystal structure on wear resistance and the fact that the eta carbides form at different points in the matrix which would then seem obvious to alloy the possibility of different materials properties. It is clear that some carbides (epsilon carbide) are known to be directly inferior to others (cementite). Or would you argue against this as well?

-Cliff
 
I did some more reading to try and get some quantitative information on the extent of eta carbide formation. Studies at the Jassy Institute in Romania found an increase of over 140% of small countable carbides, from 33 000 per square mm to 80 000 per square mm.

"Tool Steels", by Roberts, Krauss and Kennedy, also describe several forms of carbides in steels and note that eta carbides are extremely wear resistant, much more so than several other types.

The National Bureau of Standards has also stated that cryogenics induces gains in wear resistance due to the precipitation of fine carbides, and that this precipitation reduces the stress in the martensite and thereby reduces the susceptibility to cracking on a microscopic scale.

Further in regards to retained austenite, in "Melallury of Tool Steels", by Payson, several steels are noted in which tempering does little to transform austenite (O1 and L6), however it does condition it by lowering the solutes so that it will transform after tempering to then untempered martensite.

The untempered martensite induces an obviously brittle structure which is stated to be a common form of tool failure. Colder quenching is listed as a way to solve this problem. It seems obvious here though that multiple tempers would also deal with the problem though indirectly.

Note, Pete Paulin CEO of 300 Below Inc. has posted regarding cryo in the shop talk forum :

http://www.bladeforums.com/forums/showthread.php?s=&threadid=219930

-Cliff
 
Accurate Plating said:
Ceraguard is the newest Accurate Plating and Weaponry Firearm Coating offering excellent corrosion protection, outstanding abrasion resistance, hardness and durability…
The 'H series two component ceramic hybrid Gun Coatings were designed to provide a high quality, long lasting finish. After a full cure they have excellent resistance to most solvents and chemicals. At Accurate we oven cure the parts for maximum durability.
That's "WEAR" the similarity ends. Tests have shown almost a 60% gain in wear resistance according to tests by an independent lab...
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Mete & Ed

wondering about this...would like to know from any metallurgist, and wonder if can be applied (to knife/blades) after all heat treats/hardening/cryo etc... already done??
 
I am about to send a five D2 blades to Texas Knifemaker Supplies for heat treating. The cost will be $5.50 per blade. I can get the cryo for an additional $4.00. The steel was expensive, and the handle material I plan to use was even more so. By the time I am finally finished I will have many many hours invested into these knives. Three of these knives will be gifts. Two of them will be for me. I plan to carry at least one of these knives with me every day for a long time. So--considering all the work and money I'm investing in this, do I spend a mere $4 on a process that might help and can't hurt?

Scott
 
Scott, go ahead with your plan sending them to TKS. Before I started HTing myself, I had them do all my D2 blades with cryo and they do a very good job.
Scott
 
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