cryo-treating parts

[jpnovak]

I know that people cryo-treat many steel parts. I know some of the metalurgy of how it works to covert austenite into martensite. I know its used on brake parts to reduce wear and increas life.

Is this process good for other parts in an engine? What about cranks, rods, crank gears, cams, rockers, pistion wrist pins, rings etc? Charles Navarro from LN Engineering recommended to do this to steel cylinders for increased life.

Anyone have any direct feedback to doing this? Anyone know the cycle times? I have read the gas method is best and its an 8 hour cool, 12 hour hold, 8 hour warm cycle.

I have access to LN2 and am not afraid to use it...

[camgrinder]

Keep the camshafts out of the cold stuff. The camshafts I have seen which have been frozen bend like crazy.

[350HP930]

As John states, one of the known downsides to cryo treatment is the possibility of the object distorting.

If you do a set of rotors or cylinders its best to do so before final machining so the item can be trued after the treatment.

You are also limited to homogeneous materials. cyrotreatment could destroy a set of nikasil cylinders due to the different coefficients of contraction.

[strokher racing]

I had my billet cylinders cryod. Cast aluminum seems to benefit the most from cryo. There is no reason to cryo a cam that is not a place of issue or concern like John states.

Eric Hood

[snowman]

My MB has cyro treated cams. How did they do it???

[cnavarro]

I've never had any parts distort from the process. The benefits of the process are most noticeable with cast pieces, steel the greatest, then aluminum and magnesium (great for 2.7 cases as well as vw as21 and as41 blocks). The improvements are then lesser for forged and the least for billet (from extrusion), due to the inherent grain structure through the manufactuing process for the material. Where it does help however in forgings and billets is in the area of fatigue life, not strength. I like to cryo our billet cylinders for turbo guys since it's not that expensive, although it's really not needed.

I have used 300 below in IL and Performance Cryogenics in Cleveland, GA, both with excellent results. I know that Air Power Racing (performance 356/912) also cryo their engines and all internals, as does Aircooled Technology (performance 914).

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[jpnovak]

Interesting feedback. Thanks to all who responded.

Charles, it sounds like you have tried many materials processing steps in your research. From the Cryo-treatment in this thread to responding about my previous questions about Thermal and lubricant coatings. are there any other processing steps you have tried with good or bad results?

[cnavarro]

Thermal dispersant coatings were a total wash other than keeping cast iron from rusting. Other than that, I can't complain about the multitude of coatings I've tried from Calico Coatings and Casidium ($$$), they all were very valuable in the performance or improved reliability each coating provided. I probably would steer clear of any coatings on the valve stems with exception of Casidium, a nano-diamond like carbon coating, which is also applied to the tulip portion of the valve. Originally the stuff was designed for coating Ti to help it last longer.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[David]

I remember learning in an alloys class about how sub cooling steel will convert some retained austenite to martensite, but what's it supposed to do to aluminum?

[cnavarro]

For aluminum, it's supposed to improve fatigue life and in castings, improve the grain structure as well.

Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance

[350HP930]

In addition to improving grain structure cryo treatment will also get rid of latent material stresses like annealing does.

[cnavarro]

I'm glad you pointed that out. We had a batch of aluminum a few years ago accidentially come in un-stress relieved and we used the cryo process to get rid of the material stresses build in during the extrusion process. Otherwise, all our aluminum extrusion comes stress relieved, which helps to provide a more dimensionally stable part both during and after machining and placement in service.

[jpnovak]

Interesting how aluminum will relieve stress under cold temps. I would have thought a high temp anneal was the only way. Basically input energy to overcome the reorganization of the lattice and cool slowly to lock in a particular grain structure. As a chemist that is how you isolate molecular confirmations. I guess materials behave differently.

This has been very informative. Thanks.

[cnavarro]

I always recommend cryoing used cylinders at time of reconditioning if new cylinders are out of the customer's allotted budget. It's a safe insurance policy, whether cast iron or aluminum.

[70SWT]

Originally posted by jpnovak
Interesting how aluminum will relieve stress under cold temps. I would have thought a high temp anneal was the only way. Basically input energy to overcome the reorganization of the lattice and cool slowly to lock in a particular grain structure. As a chemist that is how you isolate molecular confirmations. I guess materials behave differently.

This has been very informative. Thanks.

As someone trained in physical sciences as well, I am also amazed this process works. (Always sounded like snake oil in the past to me.) Not doubting anyone's word, just inquisitive...does anyone have links to good data/studies on this? Maybe micrographs showing before and after effects or other hard evidence of the benefits.

[cnavarro]

There is a pretty good collection of articles concerning cryogenic treatment on 300 Below's site at http://www.300below.com/site/press.html. Good reading.

[350HP930]

What I learned in my materials class was that approaching absolute zero eliminates latent streses via packing the molecular lattices as tightly as possible.