Gearbox Heat treat, Audi 016

Well,,

Given, I'll be taking apart my audi 016 transaxle for at least an inspection. I may as well think about hardening up the gear set, shafts and shift forks while am at it. The local place for me is:
http://www.garnerheattreatinc.com/capabilities.html

Not sure what is what with the hardness of the current steel in the gearbox. I guess I will have to get my rockwell tester out and find out.

any thoughts would be welcome, it cannot be that expensive to heat treat parts in bulk.. steel is steel to the heat treat folks,,, LOL I have yet to speak with garner about what they may think is best. I think surface hardening maybe the way to go. The Deep Cryogenic Processing appears interesting...


best

Heat treat

capaci,

Don’t do it!!!!! What the Cryogenic Process does is it changes all the retained austenite into martensite. Austenite crystal structure is soft and by changing it into martensite it makes it harder. This seems like a good thing, but there are 2 problems:
1) 1) Austenite that has been phase changed is now un-tempered martensite so it needs to be tempered back in a furnace to keep it from being brittle, which will most definitely cause distortions.
2) 2) The company I work for, Eaton Corporation builds a lot of differential gears at one of our plants. They've found through testing that gears tend to be tougher if they have a small level of retained austenite left in them after the casehardening heat treat process. This testing was done on gears made out of 8620 material, which used to be the preferred material do to it's high nickel content, which adds toughness. In theory the lack of any austenite should make a better gear, but we believe that having some soft material seems to helps the harder martensite crystals move slightly under severe conditions without having stress cracks start.

The main shaft and gears in the 016 are most likely 8620, which the above will apply to.

Even if they weren't you'll never make it through temper without distortion.


Good luck,

Thanks Jim

No issue

I just was thinking about it. I will call the folks and find out what is what. I may want to surface harden the gears and shafts and forks then temper. It would seem like galling and chipping maybe a problem under loading with the gears, maybe not with the proper lube.

I will ask them about distortation and the like with what I'm doing, They appear to know what is what.

Eaton has made steel parts for a long period of time in heavy duty apps. Thanks for the input. I will post what garner has to say.

Got any Idea on the 8620 hardness as audi has it OTS maybe numbers from eaton could be helpful ??

Not sure what they will say about the alumimum case.. most likely nothing! maybe something...steel plate install seems like it!

I saw the picture of the spider gears in the diff fractured from shock.. what will help this steel be more resilient ?? there has to be a process to help rather the go to a new material or fab process for the parts.
Add more steel always helps in mechanical loading... The factory did what was best for their application, It may not be able to be improved without replacement, TBD.
Best

Here what they say

Cryogenic Treatment

Cooling to a low (cryogenic) temperature, usually -100 to -320 F, to stabilize microstructure and dimensions; typically for high alloy (tool) steel parts. The treatment is carried out after quenching, or more appropriately after the first temper, to transform Retained Austenite to Martensite which is then tempered.
Garner Heat Treat, Inc. utilizes the latest in Computerized Vacuum Technology. This assures precision in heat processing by providing distortional and dimensional stability. The 5-Bar Vacuum Furnace offers unparalleled control in heating and quenching operations. The 5-Bar's ability to perform interrupted quenching minimizes the potential for distortion and cracking. Skilled operators using advanced tools and methods, evaluate each part and setup loads to minimize distortion and optimize dimensional stability.

Deep Cryogenic Process
Garner Heat Treat, Inc. offers deep cryogenic processing of products to -320oF. Cryogenic processing increases dimensional stability, wear resistance, and the performance of most alloys through conversion of retained austenite to martensite and through precipitation of finer carbides.

GHT's -320oF deep cryogenic process improves performance and increases the life of most products provided to customers.

GHT's deep cryogenic process is completely computer controlled. Products are slowly cooled to -320oF at a predetermined rate based on the material size, type, and hardness. After soaking for the specified time interval, the products are slowly ramped-up to room temperature then tempered at the appropiate tempering temperature.

Garner Heat Treat, Inc., offers deep cryogenic processing of products to -320oF. Cryogenic processing increases dimensional stability, wear resistance, and the performance of most alloys through conversion of retained austenite to martensite.


Wear Improvement of Shallow Cryogenic (-120) vs Deep Cryogenic (-320) Cycle
-320oF deep cryogenic processing allows GHT to offer customers improved performance and increased life of metal tools and parts. Other deep-freeze methods reach only -120oF. Our innovative cryoprocessing takes metals beyond deep freeze to cryogenic levels transforming almost all soft retained austenite to hard martensite. This creates a significantly denser molecular structure resulting in a larger contact surface area that reduces friction, heat, and wear. The computer controlled ramps virtually eliminate thermal shock.

Benefits of Deep Cryogenic Processing
Conversion of most retained austenite to martensite. Stabilizes alloys without changing shape or size of product. Cryogenically treating welds returns the metal to its original state. Increased durability and wear life.
What Does Deep Cryogenic Treating do?
These ultra-cold temperatures, below -310oF, will greatly increase the strength and wear life of all types of vehicle components, castings and cutting tools. In addition, other benefits include reduced maintenance, repairs and replacement of tools and components, reduced vibrations, rapid and more uniform heat dissipation, and improved conductivity. Cryogenics process is like an insurance policy for your tools and components.


http://www.timken.com/timken_ols/steel/handbook/table.asp
on the 8620..

I;m not a Metallurgist by any stretch... This is cool stuff however...

I'll check on average hardness and case depth, don't want to quote off the top of my head.

You'll note that GHT says minimal distortion, not no distortion, which means by using this process of Vacuum tempering it allows less stock to be left behind for finish grinding or other processing, but I don't think you'll get away with it on a long shaft like the main input shaft this would typically be finish processed after this process. You might get away with it on the removable gears.
Check the thread that Ron started, you'll see that the Trans holds up well other than the spider gear failure and that can be fixed by running the LSD from a 944 which has 4 spider gears instead of 2.

Good luck, keep me posted.

I did call them

The engineer/Metallurgist will be in the shop in the morning.

New carrier with 4 spiders maybe the update.

I will get a quote and post it, ROM, on bulk parts like gears and shafts and talk about distortion. Unclear on the Geo tolerance is for the parts on buildup. we shall see. I will ask about long shafts without a doubt and what can be expected.

Thanks Jim

Hi ya Jim

Ok this is interesting
http://www.300below.com/site/flatout-apr04.html

It appears that I'm not the only one thinking about this and doing it.

I may have to get two 016 boxes and see what happens.
They apparently do whole engines and the crank and cam are fine with the distortation issue.
http://www.metal-wear.com/racing.htm
http://www.metal-wear.com/More%20Detail.htm

I've used 300 Below several times over the last 5-6 years to treat drilled & slotted brake rotors and the results have been excellent. They're far less prone to stress cracking and their wear characteristics have improved a good bit.

I've always been curious about treating an entire assembled engine or gearbox and what effect it would have on clearances when/if certain parts would "grow". Hence, I haven't been brave enough to do it.....

I hope they say it will work just fine and you can give it a try. It would be a fairly inexpensive way to make this trans even stronger.

Keep me posted.

Good luck,

You might consider shot peening or vibratory polishing as an alternative.

I have yet to call the local folks. I kinda hope it works out also. The work hardening methods are not cheap either.

Here are the prices from these people
http://www.metal-wear.com/racing_component_prices.htm
Gear, Ring and Pinion
Cryogenic TreatmentProduct #19$40.00
/eachCryogenic Processing reduces wear and tooth breakage, greatly increases the life of the gear.
Gear, Spider
FerrousCryogenic TreatmentProduct #31$3.00
/eachCryogenic processing reduces wear, increases fatigue life, increases life.
Gears, Differential Quick Change Gears, set of 2
Controlled Thermal Processing, Inc. Automotive Price List
Cryogenic treatment of parts not listed is $6.50 per pound. We will be happy to quote prices for coatings of
parts not listed. For unusual or exotic alloys or parts made of plastics, ceramics, etc., please consult our
metallurgy department We will be happy to work with you on unusual wear or breakage problems. If you
have any questions, please call or email us. We will be delighted to talk with you.
ControlledThermal Processing, Inc.
3627 Washington Street, Park City, IL 60085Phone 847 651 5511
126 French Belk Road, Mt, Ulla, NC 28125Phone 704 660 3326 Fax 704 660 6467
email [email protected] Visit our web site at http://www.metal-wear.com

OK Jim

I called ControlledThermal Processing, Inc.
No issue on the distortion when tempering, the temp is like 300degF way before the transition point for 8620.

They are doing complete BMW and Jerico boxes no issues with growth on part dimensions.

The price for "all" steel internals is $130.00, The Ring & Pinion is like $40, or 6.50 a pound which ever is cheaper... I may well give it a try..

best