Ive read up on the basics but after hours of searching I cant find an answer. Can you do both shot peening and cryo treating to say a tranny gear set?

 

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I don't see y not. They are both used to strengthen parst, however according to a lot of people cryo treating is not for gears. The link provided has some good info as to y its not a good idea for gears

http://forums.nasioc.com/forums/showthread.php?t=64227

 

cryo treating i thought was more for cranks and rods? for gearset they do the rem isf process witch helps alot with reducing friction on the gears. i had my ring and pinion done when it was out i did not get to hold the finish product up close but from pics you could diff see a difference. but they have come out with so many coating and process and some will say it works while others say never use them. in the end i just got with what the builder wants to do.

 

REM ISF process hands down, tranny shifts like butter.

There is a place in Georgia that is really good at it, they do much of aviation and automotive

 

you can do both. cryo should be last treatment.
dont bother with subi tech on the cryo subject. their gears are so weak they would never notice a 10% increase in strength.

I have very good first hand info that cryo helps stop breakage. many years ago the first 9 second FWD dsm was breaking axles every 2-3 passes. after the axles were cryoed they lasted 20-30 passes. drill bits and knives stay sharp way longer. brakes and clutches last way longer as well.

 

Ok, well sense you can do both would you get the full added strenght from both? TRE says shot peening adds 20-25% strength and cryo treating ands 10% so would the gears actualy be 30-35% stronger?

 

percentages dont add like that i think

100

120-125

132-132.5

 

Shot peening adds substantial strength against fatigue. Cryo is also a benefit. I'm not sure why you want exact numbers, but it really does not matter. Both help longevity.

TRE is the only tranny manufacturer in the Evo world that has the proper equipment to shot peen parts right.

 

Im not looking for eact numbers, I was wondering if you have both done would it actualy be much stronger than just shot peening. If the processes over lapped and cryo treatin after shot peening only added 1% then its not worth it, money wise.

 

I'm not going to say if any of them work or not, just going to give a little information on the processes.

Shot peening adds surface fatigue strength by inducing compressive loads that close up surface defects that can propagate deeper into the part as cracks. It actually induces a tensile stress under the surface though which can lead to sub-surface fatigue where cracks can form under the surface that can not be seen with normal NDI methods. The reason it is beneficial for gears in this case though is the compressive pre-stress on the surface reduces the tension stresses induced at the edges of the contact zone as the gears mesh which reduces the stress amplitude seen during operation. Reducing stress amplitude increases the total number of cycles (on average) the part can undergo before failure.

As far as TRE doing it correctly, that is pretty hard to state since gears are extremely difficult to do properly because of the curved surface of the gear face will change the shot intensity greatly as the part is processed. Not only can you under process and do little to improve strength, you can over process when shot peening and create very large tensile stresses under the surface of the part. This will lead to local plastic deformation and sub-surface failure.


The success of cryo treating is HIGHLY dependent on the material. Some materials will gain a huge amount of strength AND toughness with cryo treating as it will complete the austinite to martinsite phase transformation process. On some materials, it can cause volumetric phase changes during processing which can reduce internal stresses at room temperature. On other materials, it won't do ****.

ISF removes surface microstruture defects through a polishing process. The benefit here is to reduce the number of initial defects that can grow into future cracks. It won't change how the cracks grow once they nucleate, but it gives you a "clean sheet" for fatigue cracks to randomly start from instead of having pre-existing defects like tooling marks that are cracks to start with before operational loads are ever carried by the component.


To summarize, shot peening is about closing up pre-existing surface defects and preventing future crack nucleation by inducing residual stresses at the surface. Cryo treating is about material phase changes to improve material strength and reducing residual stresses to reduce crack nucleation. ISF is about removing pre-existing crack nucleation sites.

 

You stated cryo treating depends on the materail, so will it work good on the tranny gears, shafts, forks, etc?

If you were only going to do shot peening or cryo treating which one would you do?

 

I have no idea if the EVO gears would benefit from cryo treatment. It all depends on the alloy of the metal.

I've always doubted cryo-treatment simply because as you reduce temperatures, atomic diffusion drops like a rock and the likely hood of cold temperatures changing the material is slim. There is solid science behind it FOR CERTAIN ALLOYS and I've just never tried it out to see how it works. You have to watch out though because there are lots of companies that will sell you their treatment enough though it may do absolutely nothing for your particular alloy.

Shot peening is actually kind of "black magic" too as you can definitely "over peen" a part and cause more harm then good. You are physically deforming the metal surface as well which with my experience with gears, the clearances on gears are pretty particular and you need to know what you are doing or the gearset will eat itself.

My personal opinion when it comes to gears, I send the parts to somebody I trust and I follow their recommendation for my application. I'll jump into just about anything except for gear sets...

 

As far as a gear treatment goes I'm of the opinion that the gear case on the evo has more issues than the physical gears themselves. I think a friction reduction is the best gear saving process out there for big power cars as that is the only way to really stop gears from wearing out.

 

Spoken like a true mechanical engineer lol

Thanks for the info . I had been wondering for a while about how cryo treating/shot-peening gears would actually help strengthen them, but its been awhile since I took a materials class