We always solution anneal Maraging material once again before machining. I haven't checked the hardness results from that condition yet.
If it is a surface issue, that would be much easier to rectify.
Are "failed" heat treatments typically just reheated?
Thanks for the info @mfgenggear - that's interesting that the core hardness may be to spec but the surface drops off.
If that is the "case" (no pun intended), we may end up having the parts Ion Nitrided as we were considering testing the effects anyway.
My main concern is reduced strength at...
I don't have details on their equipment yet, but they heat treated C350 without issue. This is their first time with Maraging steel.
If it wasn't an inert gas or vacuum furnace, could the material have the scale removed and then reheat treated in a vacuum furnace?
HT was done by a supplier that is normally very reliable. Could be a material issue as well.
My first thought is run it for 10 hrs, but I'm not a materials expert...I have no idea the effects of reheating the material.
Maybe a cryo treatment would convert more Martensite and harden it up too?
We just had some Maraging C300 parts come back from a standard aging process (6 hrs @ 900F, air cooled) with a 47.5 HRC hardness.
Typically it should be 50-55 HRC. What would be the best course of action to achieve higher through hardness without case hardening or nitriding?
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...
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...
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...
Finally got a chance to test the new C350 parts.
Gave us about 35% more torque capability in failure testing over 4140. Haven't done fatigue tests yet.
Would love to get a hold of some Aermet or Ferrium alloys.
@EdStainless
What material did you end up using for those shafts if you don't mind me asking?
Was it the 4335 Vmod you mentioned?
May end up being that a lower strength but tougher alloy will perform better than the C350.
We'll have to test and find out.
The splines have been shot peened in...
The load is fully reversing (bi-directional).
Those are some really interesting suggestions about pre-stressing the part or shot peening under load - never heard of that before. On FEA, the stress was reduced without the center bored out. Maybe a certain diameter will show an improvement...
The existing design works at our current loads.
We are looking to drop-in a higher performing material so we can raise the input torque.
It is a "legacy" design that we can't modify any further.
Torque is applied gradually with minimal shock loading. Splines have not contributed to failure...
@EdStainless
The transition is as long as possible (mating parts dictate the maximum size).
One thing is, now that it is an elliptical transition, the machining toolpaths will be more prominent than using a standard radiused corner bullnose endmill...
It will be blended by hand to eliminate...
Based on SN curves, Ferrium C61 and S54 look like they're almost as good as it gets.
I found this previously, thought it was a nice toughness comparison of high strength materials:
https://www.carpentertechnology.com/blog/toughness-index-for-alloy-comparisons
@mfgenggear
So, focus on material fatigue strength at 1E4 cycles?
C350 has a relatively low fatigue life - 110 ksi @ 1E7 cycles I believe.
The part has been analyzed with FEA, but it fails at higher loads than calculated by hand and FEA.
Maybe it is strengthening past it's yield point?
The failure mode is always ductile torsion failure right at the radius where the input to the shaft steps up to meet the splines.
I should add that this is not a typical "shaft" - it's used in a static loading application. 0 RPM.
4140 has acceptable service life, but at lower torque than is...
We're looking to maximize the amount of torque we can apply to a short splined shaft (~10,000 reversing cycles). We have been using 4140 previously.
What would be the most important material property to achieve this? We are looking at Aermet 100, Ferrium C61, MP35N... Seems 300M is recommended...
For anybody interested, I finally got around to machining the piston on a harbor freight lathe.
I posted the pictures here: https://www.practicalmachinist.com/forum/threads/line-boring-metal-3d-print.408998/page-4
Went to get advice from that forum and ended up getting the usual, BAHHHH it's...
Yes, a steady state dyno won't show increases in BRAKE power because the reduced reciprocating inertia isn't being accelerated. But I don't see why this matters. That extra initial 1.5 kW (2hp) does have an effect during acceleration. The engine will be used dynamically on a dirt bike, not...
