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High tensile strength alloys for 3D printing?

Terry Keeley

Titanium
Joined
Oct 18, 2005
Location
Toronto, Canada eh!
Looking into getting some propellers printed for my R/C boats and not finding a lot of info.

I'm currently making my own wax (just starting to 3D print it) and having a jeweler investment cast them in 17-4 stainless, as cast they're around 185 ksi UTS and are working well.

Was wondering about going directly to printing but the only alloys I'm seeing are probably not strong enough. Shapeways shows 316L that is 84 ksi and a bronze/steel mix that is 99 ksi.

Any info about printing 17-4 or similar? I see some shops doing 6Al4V that's around 130 ksi but I'm sure the cost is prohibitive.
 
Any info about printing 17-4 or similar? I see some shops doing 6Al4V that's around 130 ksi but I'm sure the cost is prohibitive.

You might as well get a couple quotes for Ti from service providers, I'd imagine that the bulk of the cost is the machine and process, with materials being a smaller component.

You could contact someone like Markforged to see who provides service using their equipment, they do have 17-4 as well as some tool steels and Inconel 625:

3D Printing Materials | Markforged

Curiously, they don't seem to offer Ti yet.
 
I'm currently making my own wax (just starting to 3D print it) and having a jeweler investment cast them in 17-4 stainless, as cast they're around 185 ksi UTS and are working well.
You have a source for small quantities of investment cast 17-4 at a price that hasn't bankrupted you and you're unhappy ?

Terry, there's a time to go out on the front porch, smell the gardenias, have a cold mocha latte and watch the sunrise .... don't the gods punish people who are too greedy ?
 
You might as well get a couple quotes for Ti from service providers, I'd imagine that the bulk of the cost is the machine and process, with materials being a smaller component.

You could contact someone like Markforged to see who provides service using their equipment, they do have 17-4 as well as some tool steels and Inconel 625:

3D Printing Materials | Markforged

Curiously, they don't seem to offer Ti yet.


Thanks, did quite a bit of digging and didn't see anyone printing 17-4, I'll give them a call.

edit: musta been putting the wrong mix into the Google machine, looking for "3D printing" and "17-4" gets lots of hits.


You have a source for small quantities of investment cast 17-4 at a price that hasn't bankrupted you and you're unhappy ?

Terry, there's a time to go out on the front porch, smell the gardenias, have a cold mocha latte and watch the sunrise .... don't the gods punish people who are too greedy ?


Ya, I know, you're right of course. A tune comes to mind:

Queen - I Want It All (Official Video) - YouTube
 
I should take Manny's advice and just keep getting them cast, it looks like the process for printing 17-4 is complicated ($$$) and the results I've seen are less than spectacular. I do have to do a little post machining but that's no biggy, was just thinking how cool it would be to have a (nearly) finished part perfectly balanced right off the printer.

Here's what I'm doing now to give an idea (sorry - hobby alert)


full



full



full
 
Beautiful prop !

Qs:

Whats the approx size D / L ?

What ballpark pricing are You aiming for ?

Fwiw..
Afaidk,
the "strength" of a prop needs to be fairly low.

Wooden props even from inferior woods were quite good enough for aircraft props, for example.
And HTD pulleys made from alu are good for 20 HP in very small sizes, meaning that alu is several times stronger than needed for a prop with much bigger dimensions aka "strength".

The material "strength" needed for a boat prop is probably about 0.5 - 0.2 the strength of alu.

As in any much weaker sintered 3d printed metal vs solid will probably work just fine, for a boat prop.
Imho.
I´m willing to learn if anyone has sources ..
But in 20 years of yacht related stuff I´ve never seen prop strength been an issue- nor anywhere near.
(Stainless race boat props, very large and thin, 500hp+, are not a good comparison.)

I think .. cogito .. For an rc craft any metallic material should work, just double dip it (coat) in epoxy of choice.
It´s not a liveaboard cruiser meant to go for years in saltwater.
 
Qs:

Whats the approx size D / L ?

What ballpark pricing are You aiming for ?

Fwiw..
Afaidk,
the "strength" of a prop needs to be fairly low.

Wooden props even from inferior woods were quite good enough for aircraft props, for example.
And HTD pulleys made from alu are good for 20 HP in very small sizes, meaning that alu is several times stronger than needed for a prop with much bigger dimensions aka "strength".

The material "strength" needed for a boat prop is probably about 0.5 - 0.2 the strength of alu.

As in any much weaker sintered 3d printed metal vs solid will probably work just fine, for a boat prop.
Imho.
I´m willing to learn if anyone has sources ..
But in 20 years of yacht related stuff I´ve never seen prop strength been an issue- nor anywhere near.
(Stainless race boat props, very large and thin, 500hp+, are not a good comparison.)

I think .. cogito .. For an rc craft any metallic material should work, just double dip it (coat) in epoxy of choice.
It´s not a liveaboard cruiser meant to go for years in saltwater.


Most of these are cast in 20C beryllium copper as it's usually strong enough (80 ksi) and casts well. As Manny said the problem with this much pitch is the blades bend and "unfold", you can heat treat them to 160 ksi but they get brittle and throw blades. I'm chasing a few world records at 130+ mph and you need to turn these at 30k rpm, a blade takes a bite about 1000 times/second, electrics have gone 200 mph at 50,000+ rpm.

You could of course make them thicker but the thinner the better. Some are using dental cobalt chrome but it's a PITA to work with needing diamond tooling.

17-4 is the best available, that's probably why full size unlimited hydroplanes use it.

It's about 2.5" in diameter.
 
17-4 is the best available, that's probably why full size unlimited hydroplanes use it.

It's about 2.5" in diameter.

How about making some from S7 tool steel? Higher tensile capability, made for shock loading.

http://www.matweb.com/search/datasheet.aspx?matguid=94107f89681048a0bed42af5a6027d96&ckck=1

The props you show can be made (I think) using any three axis CNC mill. Don't need 5X with that "open" a blade. Not even a rotary if you just use a "flip" approach.
 
How about making some from S7 tool steel? Higher tensile capability, made for shock loading.
And it rusts. And machining takes forever. I'd say Mr Keeley has a pretty damn good handle on this already.

Now if he wanted to play around .... counter-rotating, like a duoprop ? I guess supercavitating has been tried and there's trouble with keeping the props at the right elevation due to the boats being so small ? Different classes for duals and singles, most likely ?
 
Statasys, Markforged, Desktop Metal, et al, list 17-4 as an available material.

It's the lowest cost stainless steel that's easily heat treatable and distorts minimally in heat treatment.

How usable the part will be straight out of the printer is a completely different discussion.
 
For 3D printing in metals, my two go to providers are:

Additive Manufacturing | 3D Printing

3D Printing Service & Digital Manufacturing | FORECAST 3D

In that order. The guys that started AMLLC left Forecast to start their own gig. Both good companies to work with. Easy to get quotes, just submit your solid and the material you want it printed in. They even offer post processing for a fee.


Lots of good info on that first site, thanks.

Looks like the finish is pretty rough for DMLS in 17-4?

Direct Metal Laser Sintering (DMLS) : Additive Manufacturing


DMLS_inner.jpg



They have a spec sheet that shows "as built" UTS between 886 & 924 mpa (128-134 ksi) so it looks to be a little weaker than "as cast" which is H1150 (145 ksi).

I might shoot them a file for shits and grins.
 
EOS DMLS machines do Ti64 very well. That's what I started with at my current job. It's quoted to be 130ksi as printed. You're never going to get a great finish from any DMLS process, but how much is acceptable and how much they could be polished may be a different matter.
 








 
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