Cryogenic treatment of various automobile components has been a popular process lately, with even forum members proclaiming its magical results on gears, brake rotors, and other ferrous components.
This blurb was in the latest Air Products Quarterly:

"Do cryogenic treatments of steel really increase wear resistance and toughness? To help put he debate to rest, Zbigniew Zerucki, AP Research Associate, recently evaluated various heat treatment schedules, including a cryo-quenching step for processing of transformation-hardenable steels. Zurecki sought to determine if cryogenic treatments of tool steel increase wear resistance and toughness through the interplay of three effects: completing martensitic transformation(elimination of retained austenite); promoting precipitation of fine, nano-sized carbides; and imparting compressive, residual skin stresses.
His experiments demonstrated that liquid nitrogen as well as liquid helium cryogenic quenching did improve wear resistance as evidenced by pin-on-disk and by microscratch testing methods but, at the same time, reduced impact resistance. Interestingly, the work confirmed precipitation of what turned ut to be low-alloyed carbides at cryogenic temperatures with extended holding time. The feasibility of such a "cryogenic aging" has been the subject of a lively debate in the metallurgical community during the recent years.
Cryogenic quenching has traditionally been recommended for reducing the number of tempering steps required in heat-treating of tool steels and improving their wear resistance. Present results reinforce those recommendations and indicate that additional, optimizing studies are always required before applying cryogenic quench treatments to steel components subject to severe dynamic loading during service. To read more and find out how cryo-quenching can improve your steel properties, request a copy of the full article by calling us at 800-654-4567, code 337."

Air Products sells cryo consumables.

Note: brake rotors are not tool steel, they aren't even hardenable steel, they are cast iron. Production gears are not tool steel either. Nor are crankshafts, or rods. Some piston pins ARE.
So, before you spend your money on a one-size-fits-all, do-everything process of questionable value, ask the cryo vendor some hard questions. At the very least you should get before and after hardness testing performed on your expensive parts to verify if the cryo process has indeed wrought the desired changes.

Caveat emptor

Larry
code5coupe

 

Interesting commentary. Thanks for taking the time
to transcribe that here.

It was my understanding that a benefit of cryo-thermal
treatment is the effect this has on grain structure. If
so, I don't imagine that hardness testing is going to
reveal any change.

Wouldn't this require destructive testing on the part
itself or on surrogate sample pieces that had been
included in the batch?

.

 

good find

and great phrase

 

 

I certainly concur with the note about cryo treatment being ineffective for brake rotors. My cryo treated rotors cracked in about the same duration of use as a cheapo rotor after track usage. They were properly bedded in. Excellent article.

 

The article seemed to be focused on tool steel, as you point out some items that aren't. That doesn't automatically mean that they can't benefit from the cryo treatment. I am not starting an argument, because I admit I don't know. Just food for thought and a word to the wise, etc. The best advice, is in the next sentence:Always

RACE ON!!!

 

i have read it does help hard street driven rotors

 

Brake rotors on the track spend extended time at high temperatures, this will most likely eliminate any of the microstructural phase transformation benefits that result from the initial cry treatment. If you re-cryo after every track day, that might help to extend the life of a rotor.

Cheers,

Lawrence

 

Yeah, I'm thinking this is what is actually going on.. Your making your money with cryo-treatment by going from marsinite to arsenite... Which can be reversed with heat.

I think this article is misleading because not only can you go from marsinite to arsenite but you can also use cryo treating to remove internal stresses. I know DCT can be used on titanium alloys and aluminum pieces.


Admittingly my old engineering books have nothing on this subject.. My guess is its still relatively new. Its hard to find good info that isn't clouded by a sales pitch.

 

Makes perfect sense it increases hardness but decreases flexability.Just like freezing water...... now I wonder about the trade off.Do rear end gears need any flexability?Will they shatter easier?

 

Makes perfect sense it increases hardness but decreases flexability.Just like freezing water...... now I wonder about the trade off.Do rear end gears need any flexability?Will they shatter easier?


Do we have any actual experience comments about cryo treatment of D36 parts rather than going to D44?????? I have been considering doing it to my D36. And I am way in over my head on whether this is worthwhile or not. (Purely a cost issue)

 

I just cyroed my D-36. I got a killer deal on it and couldn't pass it up. As for testing, i don't have low 10's in the plan for next year ( no more without a roll bar), but i will be running some high 10's with high 1.4 60' and low 1.5's. Of course i have already done this with my current D-36 and have had no problems...so far. I'll keep you posted when summer finally gets here.

Mike

 

 

So what was your best ET with the stock D36?

 

Somewhere around 10 years ago, Popular Mechanics send some typical home tools for cryo treatment and then tested them for wear against the same tool that wasn't treated. The treated drill bits I recall lasted no longer than the untreated tool steel bits and most of the tools did not benefit from the treatment.
I know an avid varmint hunter that goes to Wyoming for a week each summer to shoot at prarie dogs and uses an accurized AR-15 and shoots 300 to 500 rounds a day. One problem he has is the advancement of the throat of the firing chamber (gas cutting erodes the barrel just ahead of the case mouth). For highest accuracy he (and so do I) seats bullets in his cases to about .015 inches from the lede (the start of the rifling). Throat erosion advances the lede and harms accuracy. He had a new barrel cryo treated and measured the barrel hardness on a Rockwell machine before and after and his barrel (not tool steel) gained about 5 points on the C scale. Also he was amazed that he measured no difference in throat dimensions after a week and thousands of rounds of shooting in Wyoming. It takes a lot of expensive testing to determine if cryo treated metal parts had any benificial effect!

 

10.26@126 1.46 60'

 

Yes, it would.

Generally, increased resistance to wear comes from increased hardness. This is particularly true of the steel alloys. Grain structure changes can have many effects, not all of them desireable.

Larry
code5coupe

 

Gears subjected to heavy loads (e.g. differential gears; spiders, ring, and pinion gears) are one of the most difficult heat-treating subjects. They must be hard...to minimize wear...yet tough, to withstand tremendous shock loadings. "Flexibility" is part of toughness. Most gear makers have spent much effort at arriving at a heat treatment that will yield acceptable amounts of both wear-resistance and toughness.

If I were considering an aftermarket treatment of new gears, I would have to look at the new ion coatings...titanium nitride being the most common...that have been demonstrated to reduce wear. These coatings would reduce wear without affecting the already-proven toughness of the manufacturer's heat treatment.

Cryo as a stress-relief process has been claimed, but never proven.
I would be somewhat skeptical, since proven stress relief processes involve putting energy INTO the metallic part, whereas cryo involves the opposite; REMOVING (heat) energy....at least temporarily.

Speaking of temporary; if re-cryo'ing brake rotors is required after every track session, it would make more sense (hassle- and money-wise) to just buy new rotors each time.

As far as cryo being effective for titanium, 80% of my company's products are titanium. Heat treating is among the processes we use. We've found no evidence that cyro is a valid process on this material, at least not in the more common titanium alloys that we use. (6Al-4V, and 6-2-4-2) For sure, none of our customer's specs (including GE, Pratt&Whitney, Rolls-Royce, Allison, Boeing, Lockheed, and others) allow cryo in our manufacturing. At least, not yet.

Be interesting to see what future cryo has in the aftermarket. So far, it seems to have limited application, mostly on aluminum alloys and specialized tool steels.

Larry
code5coupe

 

Actually cryogenic treatment RARELY increases hardness as evidenced by Rockwell testing with the lone exception being cast iron (particularly graphitic cast-iron). That's one of the reasons we see increases in brake rotor life. I do understand that some people have failed to see results, but I have enough business from fleet agencies and racing teams that testifies it does indeed help with longevity. Perhaps it depends upon the alloying content in the iron, I can't say but the majority of our finding indeed backs up the claims that cryo-treated rotors last longer...As do cryo-treated engine blocks and nodular crankshafts. Perhaps what a majority of people forget about cryogenic processing is that it does indeed have other benefits besides simply making something more wear resistant...One of its chief attributes is stress-relieving. I actually first learned of cryogenic processing in the mid-80 when I was shooting on a junior benchrest rifle team. Our rifles were seldom more than 1/4 MOA (minute of angle) which equates to .25" 5-shot groups at 100 yards... Most would shoot markedly better than that...And they were usually cryo-treated barrels. The stress relief caused a positive change in harmonics and some barrels have increased by better than 30% after treatment. A side benefit in this case is a slight increase in muzzle velocity (due to friction modification I assume) AND the requisite increase in wear resistance which was pretty extreme in the throat area of these hyper velocity benchrest rifles. That was 20 years ago... I actually process barrels for a lot of these guys now, shotgunners as well, and my crowning achievement here is having my cryo-processing used on .50 sniper rifles that are shooting terrorists in Afghanistan and Iraq!

But, back on the context of vehicles, stress-relieving is key in nodular iron. As anyone familar with cast iron knows, it is not heat treated but work-hardened after casting. And, cast iron wears relatively well for that. But the problem is that part of the heat treating process is tempering for stress relief. Since there is no heat treatment of cast iron there is no stress relief and ANY TIME a material is cast, forged, welded, machined, or otherwise any invasive action performed upon it residual stresses are created. The number one cause of death for a nodular iron crankshaft is stress fracturing! The cryo-treatment eliminates this largely; I've got customers from NHRA Stock Eliminator racers (who like iron because it's lighter than forged but hate it b/c it's weak) that run 9000 rpm to Turbo Buick guys and LS1 guys that are making 1000 hp on stock cryo-treated cranks.

Another benefit is dimensional stabilizations...You can find guage manufacturers like Browne & Sharpe, Mitutyo, Starret, and others on cryo-processor's client roles. They process guage blocks and mic anvils in order to ensure their stability. Once the grain is refined and set through the cryo process they are ensured of an accurate guage. Additionally they use it for the more mundane purposes of lengthening their tool lives as well. But this can cross over to automotive by looking at the relationship between an aluiminum piston and a cast iron cylinder bore (or liner). Aluminum grows faster than cast iron and eventually you start to have eccentric wear which causes the loss of ring seal. This is greatly reduced on cryogenically treated components due to a more stabilized growth between the two. One of my customers has a 2200 hp diesel tractor-puller that runs just shy of 80 psi of boost. He tore the motor down twice a year up until three years ago. He was one of my first customers and the motor has had the pan pulled off and a main cap the last three seasons, an inspection performed, and then buttoned back up... Eccentric bore wear was hardly measurable whereas in the past it would have new liners/pistons installed every year. Eccentric wear on the turbocharger shaft/bushings was also virtually eliminated.

Truthfully there have been countless studies done by universities, and metallurgical societies; the majority of which are incredibly favorable. However, the funny thing is NOBODY, from the most brilliant metallurgists and engineers to the layman using an end-treated product can explain EXACTLY HOW or WHY it works on so many different materials (from ferrous and non-ferrous metals to some composites and even electrical carrying components), but most conclude it does indeed work. I'm in the middle of a research project in the timber industry with one of our colleges on the benefits of cryo-treated chipper knives in the chip mill industry; so far the results have averaged a 221% increase in lifespan and a 400% increase in chip quality on 400-series stainless chipper knives.

The majority of my business is focused on motorsports because that's what I'm the most heavily involved in and that's what I concentrate...Much to the chagrin of my banker who believe (and probably rightly so) that I need to be after the industrial segment. That's slowly coming to fruition but coincidentally it's in processing the tooling of motorsports manufacturers!! Anyway, there are always detractors and the FACT is, it doesn't always work and it's not a cure-all for crappy materials...
-Jeb

 

Jeb, if you'd simply said "I have many satisfied customers of my cryogenic service." I could not possibly argue. But, some of the statements in your post are not supported by modern metallurgy.

The lesson here: Some of the people/processes promise things they cannot deliver. Some of them can deliver, and do. Just be aware that it may be difficult to differentiate between the two....and keep your eyes open.

Larry
code5coupe