Material and Heat Treat advice needed for extreme ATV CV Joint.

[ATVextreme]

Looking for input on selection of material and heat treat for components in a Rzeppa style two fixed joints with plunging spline CV axle. The design is for an extreme ATV with high angle axles over 30 degrees and large aggressive mud tires. The goal is to design the “ultimate” ATV axle. Intend to use either 4340 or 300M or a combination of the two on the various components: shaft, cup, cage, and race. Heat treats considered:

1) 300M through hardened to 42-47Rc and induction to 53-60Rc
2) 300M through hardened to 52Rc
3) 4340 through hardened to 35Rc and induction hardened to 52Rc
4) 4340 through hardened to 42Rc


Any advice on applying these heat treatments to these components for this application. Open to any suggestions.

 

[MikeHalloran]

It's 'art', not 'design', until you know the stresses.



Mike Halloran
Pembroke Pines, FL, USA

 

[CoryPad]

CV joints need wear resistance, so a surface of ~ 60 HRC is important. Based on the options identified, I would go with #1.

 

[swall]

What is the intended usage? If for competition, you may want to adjust the heat treat for toughness at the expense of durability.

 

[ATVextreme]

This would be more competition than high mileage. I believe that the two stage heat treat would give a tougher part and still have a hard surface to give good wear resistance. I also understand that the 300M is substantially tougher than 4340. The question for the experts is if the RHC values specified are optimized for toughness? I believe through hardening 300M is capable of 270ksi UTS and 4340 would be capable of 200ksi UTS. I have read that 4340 would be too brittle to through harden to 50 HRC or above. I am not very familiar with 300M other than it is expensive and extremely tough. Is it much more difficult to machine than 4340 before heat treatment? I have no idea of the impact on UTS or yield strength from induction heat treat.

Thanks again for help with the "art" project. I tried to do my homework before posting. I came up with these numbers by studying this forum and other reference material.

 

[CoryPad]

High surface hardness is needed for wear resistance and to withstand indentation/embedment from high surface pressure. With the words extreme and competition, I think this will be an important consideration for your application.