Planetary Gear Material- 9310, any tool steel viable? 2

[MC6]

I am looking at making a few different involute tooth planetary gearsets, predominantly using EDM machining, with a post EDM surface treatment (to remove re-casting). I cannot say for sure that "production" will move away from EDM to be certain, but the process may move to broaching or hobbing down the road.

This is for a racing automotive application, but prototypes need to be tested first. Is something like A-2 or even D-2 viable for a prototype test piece? Or is a low 60 hrc just not enough?

I have read that tool steels can be used for gears, but I can't find any information beyond that.

Are there any other alloys other than 9310 that I should consider? What about through hardening alloys, or maraging alloys?

 

[EdStainless]

It is usually preferable to use an 8 or 9 series lower C steel and case harden gears.
Carbo-nitride is a common surface treatment, though various other methods are used.
What material will work largely comes down to the stresses that you will be working at.
While a tool steel might work for a proof-of-concept unit I would be concerned about the core toughness of the gears.

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P.E. Metallurgy, consulting work welcomed

 

[MC6]

For the ring gear, would case hardening still be the correct choice? Or is the thickness small enough that through hardened material is better?

 

[Steven_D_P]

Ring gears are usually not case hardened because (usually) after hardening they need to be ground which is often not possible (or at least hard to do) for internal gears. Therefore they are either through hardened or QT and nitrided. Nitriding them will not lead to large distortions which means they don't need to be ground afterwards. Nitrided ring gears will have a higher fatigue strength for the same size compared to through hardened ring gears (or alternatively a smaller ring gear can be used for the same loads). Nitrided gears are also more wear resistant. With through hardened gears the hardness you can achieve is limited. (Edit: another option might be to surface harden the gears. This will result in a hardness that is higher than through hardening but lower than nitriding.)

At my previous work we used to specify:
1. Quenched + double tempered
2. Gas nitrided
as heat treatment for ring gears.

 

[Tmoose]

Nitriding typically has a pretty shallow case.
If the loading is too high the surface hardness alone is not all that is needed.

"case crushing"

 

[dbooker630]

Ring gears and pinions made from 9310H can be carburized and finish ground. This grade is used for racing applications.

 

[EdStainless]

If there is finishing after case hardening it is usually just a hone.
Nitrided and CN finishes tend to be very fatigue resistant because they are in compression.

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P.E. Metallurgy, consulting work welcomed