Splined Shaft - Vasco Max alternatives? 4

[MC6]

Needing to remake a splined shaft in higher strength material ("can't" resize currently... out of my hands, don't get me started). So far it seems that C300 /Vasco Max is what I'm looking for. Are there any other "latest and greatest" high yield high fatigue life, tough alloys? Or maybe something very similar in performance but easier to machine/harden? I can't imagine I'm missing something major but doesn't hurt to ask.

My main concern is this is a very small prototype run... Not sure how much I could expect on heat treatment coming out perfect. So that's also a concern.

 

[TugboatEng]

Heat treating splines causes distortion so they often require finish machining in the hardened condition which can add substantially to cost. One option for small production runs is to use a maraging steel such as 4340 to reduce the amount of post heat treatment finishing required.

Edit: I see that Vascomax 300 is a maraging steel.

 

[EdStainless]

I would not use and M-300 steel as their toughness is way lower than the M-250 grades.
Are these square splines or involute? I have blown up square splines in maraging steels.
A few options, aerospace is in love with 300M and some of its derivatives for use above 275ski.
The HT has to be done correctly and very precisely. Double temper is required even if it is only 575F.
There are some high strength age hardening SS grades.
Custom 465 will get you just over 250ksi with good toughness.
Steels like 4335V, 4340, and Hy-Tuf will only get you to about 220ksi.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[MC6]

Yes there is one analysis of a nascar shaft? I believe by nasa, and they went into 300m's stress issues. Seems just so easy to end up with a surface defect that causes failure.

4340 too I think is very heat treat dependent... I really don't have the equipment to properly verify internal hardness.

One that I forgot was C350... The issue with that though is finding someone to roll splines on a HRC 30/35.

Custom 465, will have to look into that.


Splines are involute. What do you think of the square spline causing issues with maraging? How were the splines cut? Or rolled?

I have also been fantasizing about some kind surface treated tool steel...

https://www.sciencedirect.com/science/article/abs/pii/S0924013619303929

 

[Jughandle]

Failures that I’ve seen on axle shafts typically occur at the geometric spline-to-full diameter transition, obviously from stress concentration; flat perpendicular break, not 45-deg. Check FE modeling of having a large and gradual transition. Aforementioned grades all sound like good choices (ref specs AMS 6409, 6411, 6415, 6417, 6419, 6519, 6520, 6527, 6532). Whatever it is, go with vacuum arc remelted (VAR, or VIM/VAR). Splines will be formed by grinding because of the high tolerances. (I like involute; no experience with square.) Lastly, if your project fails, management will want to know why this, why that, so make sure you have good statistics and precedents.

 

[EdStainless]

The HT of any of these alloys it tricky, we are talking +/-10F furnace precision.
We cut the splines, hardened, and then final ground/polished. We actually honed them longitudinally in some cases.
The square splines just have too much root stress, even with good undercut radius.
Be careful with rolled splines. Some of these alloys with lower temp aging treatments may not like the cold work prior to aging.
And surface defects are simply a risk in all splines.
Your matting material and fit are also a critical part of this.
And don't forget lubrication.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[TugboatEng]

If you're chasing hardness because of wear, splines can be tricky to lubricate. Greases don't work well because there is no stirring action to re-mix the oil and thickener like we see in a bearing. The oil separates by centrifugal action. Identifying shear stable greases has helped to resolve a few of our wear issues in splined couplings.

 

[EdStainless]

We used vapor deposited WS2 as a lube.
Don't be so hung up on brute strength.
Fatigue and impact are far more important.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[mfgenggear]

MC6

to use this PITA of material requires substantiate that the high strength and met lab are required. other than standard gear materials like nitralloy that is nitrided, 9310 steel that is carburized, or 4340. or 4340M, procedure like ED Stainless said is correct, this material will contract during aging, first mistake all young engineers will make, is to finish the splines before aging. the splines will contract during age cycle. and be out of tolerance.

 

[mfgenggear]

MC6
any material over 40 HRc will require a configuration to allow a grinding wheel or carbide hob. the smaller the diameter the more expensive to manufacture parts.

 

[MC6]

I see, very very valuable insight and reflection in this thread. Thank you all for your contributions.

 

[WKTaylor]

MC6... what 'splines' [internal/external] are You using, IE: Specification?

ASME, SAE, ???

Is this for automotive, aerospace, ground-power, torsion bar, etc??

Som'more [maybe] useful 'stuff'...

MIL-HDBK-400 CRITERIA FOR PREPARATION OF GEAR AND SPLINE ENGINEERING DRAWINGS

MIL-HDBK-776 SHAFTS, ELASTIC TORSIONAL STRESS ANALYSIS OF

AGMA 945-2-B20 Splines – Design and Application [inch]

AGMA 10FTM09 AGMA Technical Paper - Reverse Engineering

SAE HS-796 Manual on Design and Manufacture of Torsion Bar Springs

ANSI B92.1 Involute Splines & Inspection

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[MC6]

Thank you for the resources WKTaylor

The spline is just to fit the hub that is in use. Roughly a 33 diametral pitch 36 tooth external on an input shaft for automotive application. It's not quite that size, but very similar to.