Ultra-High Strength Material Usability (Maraging Steel)

[novateague]

Is there a general guideline for the application of ultra-high strength alloys with low fracture toughness and ductility?

We are comparing the use of Maraging C300 vs C350 in a splined shaft. Maraging's low distortion in HT is a huge plus for us.

C300 looks like the best blend of high yield strength with good fracture toughness and fatigue strength.

If there are stress concentrations (or any notches formed), the C300 should outperform the C350, correct?

Here's a full list of materials we were looking at:

What design criteria would allow the use of something like Aermet 340 or Maraging C350?

 

[mfgenggear]

Was the number run for torsional stress. Is this the only option, was contact stress analyzed, splines are prone to scuffing, pitting and lack of lube.

 

[mfgenggear]

Op
The material and properties are chosen , then the shaft size is calculated.
The only reason to use such expensive and difficult material there no room and must be used. Send out preliminary designs for quoting, and obtain imput from the gear shop or suppliers. Cost will be very expensive.

 

[novateague]

We already manufactured the design (geometry is fixed) with C350 with a large improvement in Torque capability (compared to 4140).

The question is, would C300 possibly be an improvement over C350 even though it has lower strength (YS and UTS)?

Because there are stress concentrations and flaws in the real world, would the increased toughness of C300 actually produce better performance?

 

[mfgenggear]

Op
Higher material properties will yield higher torque. However I highly recommend run the numbers will SN charts
Cycles before failure. Torsional stress does strange effects.

 

[EdStainless]

My guess is that those fatigue number are for smooth bars in bending.
We never had success with C300 and splined shafts.
For testing we used a rig with a pair of u-joints and an offset angle to generate some torsional harmonics.
Our 4335V shafts held up better.
When we were in a bind we went to Airmet 310.

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P.E. Metallurgy, consulting work welcomed

 

[novateague]

Ed, do you have any specs for 4335V Mod? I'm looking online but not finding much.

The C350 Maraging gave us 35% more torque before failure over 4140, but it was brittle torsion break with barely any twist at all. And that was heat treating below peak UTS properties so we got more fracture toughness.

This leads me to believe the more ductile C300 would perform better in service, with just slightly less torque capability.

We'll know in a month or so - just ordered some Vascomax 300.

 

[EdStainless]

Give the 300 a try, in your case it might work fine.
We worked to a spec provided by our supplier.
The alloy was basically 300M with a touch less C.
It was VAR material.


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