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cryogenic stress relieving

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Posted by: KXaggerator---------------------

Does anybody have any experience with cryogenic stress relieving with motorcycle parts such as pistons? I had a rifle barrel treated a few years back and I found an improvement in accuracy, though it could have been a caused by a number of variables such as better mating with the beading material or action when I reinstalled it. I know NASCAR and other racing groups are now using this process. Could this cut down on the number of heat cycles a piston needs for proper break-in or lead to longer piston/cylinder life?

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A Californian trying not to hug a tree!

'98 KX250
'90 KX500


Posted by: spanky250---------------------

I read an article on this a couple of years ago that was very interesting. They were comparing treated tools with untreated ones. The edges on the treated tools were much stronger and resisted dulling much better, and the metal was supposedly more resistant to fatigue and breakage than the untreated tools. I would assume the removal of pent-up stresses in the metal would result in a shorter break-in and longer life for engine parts. I am not a NASCAR fan, but I am sure they would not be doing this expensive procedure if there was no proof of benefits. I do remember seeing adds in the back of popsci (or popmech, not sure which) from companies that you could send parts to for this treatment.

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1992 KDX 250-FMF porting,two-stage power reeds, Fatty pipe, Power Core silencer,titanium rod,Wiseco Ultra-lite, Pro-Action suspension...Why didn't I take the blue pill???


Posted by: KXaggerator---------------------

Hey Spanky,
I am new to this group, so I do not want people to get the wrong impression. I hate NASCAR, I was just using them as an example. Now touring car and GT on the other hand are the shiznid. In fact, I am 10 minutes from Laguana Seca and I doubt Jeff Gordon could hang. I was just wondering if anybody in the group had used this process and felt it worth while. http://dirtrider.net/ubb2/redface.gif

------------------
A Californian trying not to hug a tree!

'98 KX250
'90 KX500


Posted by: spanky250---------------------

Don't worry KXagerrator, I took no offense, nor did I mean any to anybody else here that may like NASCAR, and I am sure there must be some fans here as popular as NASCAR is. I was simply stating that I am not a big fan of it, so I don't really follow the news or developments in that community. And I do like GT racing, as well as Formula One.


Posted by: dual-sporter---------------------

does anyone know where I can find info on the specifics of the process? i'm curious at what points is it used. i know it involved an ultra- low temperature quench (w/ say liquid nitrogen) to freeze grain growth, but if its on a piston that constantly sees temperatures above 600 degrees, what's the point???? grain growth will continue at that temperature anyway.... i'm going to e-mail a prof to see if they know anything about it....



Posted by: Mr Gadget---------------------

Check this site out:
http://www.onecryo.com/onecryo/motorsport-brochure2.htm

Just one site that I found which some data. Cryogenic stress relieving is a valid process.....I have no personal experience with it for engine components however.


Posted by: spanky250---------------------

I went to that site. Very impressive sounding. I also like how the link for pricing info conveniently doesn't work... http://dirtrider.net/ubb2/tongue.gif


Posted by: Boit---------------------

Not to be a naysayer, but I'm wondering if this process makes metals more brittle? Chain breaker pins are extremely hard, but they are also very brittle. If they are subjected to the least amount of side load, they splinter. If the cyrogenic process is beneficial for our engines, then, I would like to know.

[This message has been edited by Boit (edited 02-07-2001).]


Posted by: Mr Gadget---------------------

I would not worry about the cryogenic stress relieved parts becoming brittle. What you discribed is a part that has been hardened and lacks ductility. This process reduces stresses in the the material and improves the grain structure of the metal, but it is not a hardening process). It does work! Greatly improved stability in rifle barrels give better accuracy - and reports of greatly barrel life.


Posted by: spanky250---------------------

Wanna know something funny? Either the people at tha cryo company track people that visit their website, or an employee reads these posts, because they just sent me an email to give them a call and discuss their process. http://dirtrider.net/ubb2/confused.gif


Posted by: Rich Rohrich---------------------

Here's what Eric posted on this subject a few months back

Quote:
Cryogenic treatment is the process of lowering the temperature of a material and then raising back up at a controlled rate in order to align the molecules in a martensitic fashion. This supposed to reduce stress. Its an excellent process for things like gun barrels, or clutch plates.
One university researcher that I know sent a cylinder, piston, and clutch plate to a poular vendor advertising in the motorsports market. They then used an electron microscope to examine the structure of the material. The conclusion was that for simple shapes its effective. For complex ones like pistons and cylinders, it does'nt work.
So the advertisng claim of 3 times the life pretty much goes along with an old law school saying; "Paper accepts all ink in advertsing and litigation".
Stress in a part can be relieved or reduced in a number of ways. On a cylinder that is freshly plated, chamfering the ports and turning the top and bottom perpendicular to the bore can do a hell of a lot more than cryogenic treatment.
I find the whole cryo-motorsports industry laughable because how can a guy verify that any work was actually performed? The part doesn't look any different. Its isn't perpetually cold. It doesn't glow in the dark. Regarding the claim of 3 times the part life, how do you verify that? You'd have to have a very good dyno cell and at least 10 identical engines to get a statistical average to back it up.
Personally I'll save my money for Hagen Daas swiss almond ice cream bars. At $2 each they might be a waste of money but at least my taste buds can justify the expense!



Posted by: Norm---------------------

I'm a materials guy, and this cryogenic tempering thing peaked my curiosity. So I did some research on the process.

Here's the short version. There is a valid basis to the process, which appears to work for a very limited class of materials (hardened steels). IMO, it doesn't have a useful application to engine parts (piston, cylinder, etc.) because these parts aren't made from such materials. I personally don't believe the claims of what it can do to engine performance.

Grab a cup of coffee and read on if you're interested in details. Doing a search on cryongenic tempering, I only found one journal article - suggesting it's not exactly a hot topic. This appears to be the same work that spanky250 mentioned about the effects on tool steels. Tool steels are made from martensitic steels - this is a very hard, wear resistantm, and somewhat brittle material that is made by rapidly cooling steel from a high temperature (>727¡C). In this process, a phase transformation occurs, but it usually does not go to completion (~85% completion). By cooling the steel to cryogenic temperatures, the reaction can be completed. This is the basic idea, and it seems to match up with Eric's comments that Rich posted. The thing is, martensite is only used in limited applications - like cutting tools where high hardness is needed at the expense of toughness. It's NOT used extensively in engines (with the exception of bearings). From my understanding, this incomplete reaction is only seen in martensitic steels, not steels that are cooled at slow or intermediate rates (pearlitic or bainitic steels) - these other steels are more common in engineering applications because they are quite tough even though they are not as strong and hard as martensite. Furthermore, martensitic transformations aren't found in aluminum, which is the other major material in our engines. So I fail to see where these increases in properties are coming from. In all fairness, I can imagine that a case could be made for some stress relief in metals based on the changes in equilibrium defects (i.e. vacancies) that would disappear and reappear upon cooling and then heating, but I don't think this would have the profound effect on properties that is being claimed. Another couple of things that bugged me about the website mentioned above is they do not say what parts are being treated to get the performance increases they are claiming. They also don't give a sufficient explanation of the effects of the process on the materials microstructure/properties or even mention what types of materials it works for. This makes it seem like this is some magic process that will improve the properties of any material you throw in the freezer!

I apologize for the longwinded response. I'm a dork, and I find this type of thing interesting http://dirtrider.net/ubb2/smile.gif

Norm


Posted by: Rich Rohrich---------------------

Don't apologize Norm. Going in-depth on a topic is the whole point of this forum http://dirtrider.net/ubb2/smile.gif

Thanks for the great info.



------------------
Rich Rohrich
==

"Wisdom is not a product of schooling but of the life-long attempt to acquire it."
- Albert Einstein


Posted by: spanky250---------------------

That was some great information, Norm. That is what makes this site so great, the variety of skills and knowledge of the participants, the willingness to share this knowledge, and the common thread of the love of motorcycles and all related technologies. Your explanation was not long winded at all. It was a complex subject with a complex explanation, and you boiled it down to the fact that, for our purposes, this is just snake oil.


Posted by: dual-sporter---------------------

the aspect of aluminums not having validity also has to do with the fact that alloying elements are used for precipitation hardening. they place alloying atoms of diffrent size in teh crystal lattice, it puts the lattice under stress. by placing the crystal lattice of the aluminum under stress, it prevents the movement of the atoms, making it harder. (do i make any sense?)

the process to do this is heating the alloy to a temperature above 2/3 the melting temperature to promote the distribution of the alloying atoms in the lattice & following it with a fast quench (to freeze them there) to room temperature. then the alloy is aged at a temperature close to 1/2 its melting temperature, which in most cases hardens the alloy more, but only to an extent, it begins to soften again if let age too long (called overaging) but it will not soften back to the annealed (softest) state. overaging is sometimes used to prevent corrosion. aging states on aluminums are usually referred to as the 'T#'(T-0...T7)after the alloy designation #(1000's, 2000's, 7000's, etc). T-0 is an un-aged, t-4 is naturally aged, T-6 is peak hardness aged, and T-7 is over-aged, theera are some odd ones i.e. T-63, T-42 but generally the first # designated the basic age condition of the alloy.

with an aluminum, i can see this process actually doing some good, (if the part will not see extended periods of high temperature) by using the sub-zero quench instead of a room temperature quench in the process. doing so would appear that it would significantly increase the stress on the xrystal lattice. the problem is: with complex parts, the ultra fast quench to very low temperatures may cause problems because of cooling one area of the part much faster than another.... & could cause warpage.
other than that, i see no real results that would make an aluminum part better, or real proof that it makes much difference in the microstructure other than additional aging in the high temperature part of the process.... only leading to an overaged part, if made of aluminum.




Posted by: Norm---------------------

Dual-sporter,

Considering precipitation hardened aluminum alloys is a good idea in this context because these materials undergo similar heat treatments to hardened steels, but I don't believe that the cryogenic process will have an advantage for these materials because of the differences between the materials. As you talked about in your post, the initial heating step is to create a solid solution, and then this is quenched to lock this structure in a metastable condition. Then the reheating at a relatively low temperature is to create a fine dispersion of second phase particles (because low temp aids nucleation but retards growth of the second phase). It's this fine dispersion that creates the strengthening effect. Since the quench doesn't have as much of an effect on microstructure/properties as the subsequent heat treatment for these materials, cooling it down should have little effect. Steels happen to get something out of this treatment because the completion of martensitic transformation depends on the end temperature. By cooling to low temperatures, the retained austenite can finish the transformation to martensite.

Norm



Posted by: Boit---------------------

You guys know your stuff! Just wish I knew more so that I could follow you.


Posted by: SFO---------------------

one of my compadres, who btw built the pace singles champions husaberg motor, sent an entire motor to be cryo treated.
He has a dyno jet dyno and he said the before and after netted him 2 hp...
He said the only way to get 883 production racer rods to live was the treatment.
WTF?


Posted by: ssuperbike---------------------

If you believe in a somthing enough, you can bet you can show some kind of difference. 2hp maybe the motor was set up better after it was put back together? If you spent the big bucks to have this done, most people would find an improvment http://dirtrider.net/ubb2/confused.gif? espeacialy spending a customers money. On the other hand, 883 rod steel? simple shape? Harleys need all the help they can get. Just thought I'd stir the pot a bit!


Posted by: SFO---------------------

Quote:
Originally posted by ssuperbike:
If you believe in a somthing enough, you can bet you can show some kind of difference. 2hp maybe the motor was set up better after it was put back together? If you spent the big bucks to have this done, most people would find an improvment http://dirtrider.net/ubb2/confused.gif? espeacialy spending a customers money. On the other hand, 883 rod steel? simple shape? Harleys need all the help they can get. Just thought I'd stir the pot a bit!



There is a place local that performs this service quite cheaply for us...
BTW, The whole motor was dipped in one shot,
negating the reassembly differences.
I guess heat treating is a wives tale as well...



Posted by: Ghostrider---------------------

Ok... steel maybe, but I don't see how this can do anything with aluminum. It is stable at low temperatures and has now ductile/brittle transition. I'd have to see some solid data to believe that this process could do anything for an aluminum piston. I'd like to see any before/after material data if anyone knows where to get it. Good thread, keep the gears turning.


Posted by: motopuffs---------------------

Hello! I am going to make some fairly general statements regarding metals and cryo, and if anyone would like me to expand upon any of these points, I would be happy to. Otherwise this post will get too long, and I don’t have enough beer or fingertips or patience at this point to type more than 753 words, especially after getting booted off America Offline after having most of this typed the first time.

My background is mainly in heat treat, metallurgy, and steels, but I think some of my comments can be applied to aluminum and other materials.

By the way, great post on aluminum alloys.

1.Most, if not all, cryo companies profit off of the fact that it is very difficult for most people to prove that their treatment didn’t improve the part.

2.Cryo companies lose much credibility when they try to apply this process to a sweeping range of materials. Any metallurgist will tell you that there are huge differences just between different grades of steel, let alone going from steel, to aluminum , to cast iron, to plastic, etc.

3.Technically, cryo can be considered “heat treatment”, or more accurately “thermal treatment”. It is the removal of heat energy from a part.

4.Cryo IS effective on steels with retained austenite. This is most likely going to be a tool steel, 400 grade martensitic stainless steel, etc. which have a high alloy content. Close attention to heat treatment can greatly minimize, if not eliminate retained austenite, taking with it the major benefit of cryo.

5.Most common “martensitic grade” steels, 10-12 (AISI) series, chrome-moly, etc. will produce virtually 100% martensite with even the most basic heat and quench. I’m talking about something you could do in your garage with a torch and a bucket of water on a test part.

6.Cryo is not a stress relieving treatment. Actually, if you have a structure consisting of mostly tempered martensite with the remainder being retained austenite, you will create A MORE HIGHLY STRESSED (BRITTLE) STRUCTURE WITH CRYO, this is actually one of the selling points of cryo. Are you confused yet? Austenite, under normal circumstances, is not metastable at room temp, so if you don’t use cryo, the austenite will transform over time to more brittle untempered martensite. With cryo, you can perform this transformation in a controlled environment, then re-temper the parts at 300 plus F to remove some of this brittleness.

7.Cryogenic treatment should never be performed on steel without a subsequent tempering at a minimum of 300 degrees F, and preferably higher.

8.Dipping a complete engine? In nitrogen? Uh, I wouldn’t recommend this! In steels, this is one of the “secrets” to the process, that is the workpiece must be cooled slowly to prevent intergranular cracking. I’m not sure on aluminum, but I would be scared. There are steel parts in your engine, right? We process parts for GE aerospace, and they are vary concerned if there is any intergranular cracking. You should be too.

9.Racing guys will spend cubic dollars on any process if they think it will give an advantage over their competition. Don’t assume that the process works. That’s like assuming that Bridgestone tires are better than Dunlops because Jeremy uses them…uh, let’s save that for another time.


10.In steels, cryo transforms retained austenite to untempered martensite, and also supposedly precipitates beta-carbides. The beta-carbides thing is only visible with a very expensive electron microscope. I used to have one of those darn things out in my garage, but the wife got tired of having to park her car in the driveway, so I sold it at a garage sale. Aw, shucks. In steels, I am pretty sure that cryo does not “freeze the structure”, but rather transforms and precipitates. But aluminum may be a whole nuther ball of wax. Or a ball of aluminum (foil), for that matter.

11.As stated in another post, many steel parts such as clutch plates are probably made of a low carbon, low alloy steel. There is very little chance cryo would benefit these parts. Save your money and buy new tires (or beer).

12.If there is an employee or owner from a cryo company reading this, I have probably started a heated discussion. I speak the truth, brothers!!!





[This message has been edited by kookooformotopuffs (edited 03-19-2001).]


Posted by: SFO---------------------

I wanted to be a cryo zealot, I wanted to believe that there was something to be gained...
so I talked to one of my customers who specializes in cryo nitinol rings(this stuff is pure hell to machine), a freaky engineer type, and had him read this thread...
He said...


Hey Bill,

I agree with most of the guys. I would not expect cryogenic treatment of
aluminum to do anything good, but might cause warping if the cooling rate is
too rapid.

Tom

I stand in awe of the awesome knowledge of my edified teachers...
Your humble syncophant, Bill


Posted by: Rich Rohrich---------------------

This is a good thread and is worth bringing back up to the top.


Posted by: Jaybird---------------------

With my limited knowledge of "thermal treats" I probably have no business involving myself in this post, but I do think there are advantages to cryo-treating of some items. One in particular are guitar strings. Strings that have been cryo treated seems to be able to withstand stretching much better that those that have not. From my experience they tend to not have as good of sound (a bit twangy) but they can be stretched during normal play far more without breakage. :silly:


Posted by: motometal---------------------

I would be interested to know if the length of the guitar string changes from before to after the process.

I think strings are drawn, and have a very highly stressed lattice. Actually, somewhat the same theory as the process used to make 1144 "stressproof" steel. Wouln't be surprised if a good old fashoned tempering would provide the properties you mentioned, and this is commonly done in conjunction with cryo...

also, a few comments in response to Norm's excellent post from earlier:
we all seem to agree that the main (if not only) advantage of cryo is when it is applied to a steel part, the result of completion of the transformation from retained austentite to martensite.

when it comes to tool steels, the 85% transformation mentioned was a good example, but actually you could have a very wide range when it comes to transformation. More transfromation, higher hardness, as martensite is a much harder phase than austenite. Nickel tends to stabilize austenite, note that 300 series SS, which is almost 100% austenite, has a high nickel content. Other alloying elements have an effect one way or the other, nickel is just one example of many. While i'm at it, i'll start a list:

Variables which can effect % of retained austenite (and effectiveness of cryo):
1. specific chemistry of the steel
2. temperature from which part is quenched
3. temperature of quenching medium (end temp of part)
4. alloy depletion on the surface (see also #1)
5. cross sectional area or part geometry (actually not as critical as most of the above)

There can be a big difference in % between two almost identical parts and/or materials, even from one area of a part to the other.

Retained austenite can easilly be viewed on a polished and etched sample at 100-400x magnification.

On carburized or carbonitrided parts, the surface is normally where the retained ausenite shows itself. A post heat treat grind or machine sometimes removes the offending area, actually providing a harder surface.

austenite, schmostenite, you say!




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