Printing...steel?

"Just Jeepin'" (macintux)
04/19/2020 at 13:28 • Filed to: None

For some context, since I completely lacked any, !!!error: Indecipherable SUB-paragraph formatting!!! is interesting:

For those who may be unaware: martensitic steels encompass all standard tool steels, e.g the ones used for knives, springs, dies, files etc. martensitic means hardenable.

Being able to 3D print these into arbitrary shapes vs machining them will likely be of the most value for parts that need to be light.

I’m curious that they mention wanting to print low alloy steels, since low alloy steels tend to be relatively easy to machine. I’d have expected more interest in higher performance steels. Can anyone comment why people would want to print in low-alloy martensitic steel?

The article doesn’t address this, but, the martensitic transformation typically changes a part’s volume by ~4%. that can make it difficult to make precision parts unless final finishing happens at full hardness. I wonder if this process results in direct production of martensite, or if the parts still need heat treatment.

To me, this is a very interesting process, but doubly so given the possibilities of generative design. For those who want to visualize why you might want to 3D print steels vs machining them, think more about brackets and support structures than turbines, and take a look at some generative design parts.

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DISCUSSION (5)

jimz > Just Jeepin'
04/19/2020 at 13:42

yep. it’s not like 3D printing with plastic, which is more or less kind of a computer controlled hot melt glue gun. 3D printing of metal is a lot more like SLS where you have metal powder, and a laser or other heat source sinters/fuses the powder together into the desired shape. The problem is that it’s hard to control higher alloys of steel; when melting/sintering the particles together the alloying metals can precipitate out and you don’t have the desired properties in the finished part anymore.

SBA Thanks You For All The Fish > jimz
04/19/2020 at 13:51

I’ve often won dered how this works at all on high-precision, high-strength parts in those alloys. Space-X has apparently been quite successful using it inside rocket motors, but as you correctly point out-- you lose a lot of the basic alloy properties in the process of 3-D printing.

WilliamsSW > Just Jeepin'
04/19/2020 at 13:55

That’s really cool. From the commentary about porosities, I’m guessing that the printing process is depositing martensite. That seems possible, perhaps by printing slowly and having the base structure be the source of the quench.

Martensite is very hard, but also brittle and prone to cracking. Porosity greatly weakens martensite.

Cool stuff!

just-a-scratch > Just Jeepin'
04/19/2020 at 13:58

I only know enough to be dangerous on this subject, but as I understand it printing metal is done using a tightly focused heat source like a laser to dinner metal powder in a low oxygen environment. I don’t see a reason this would not work with high alloy steels.

Tekamul > Just Jeepin'
04/19/2020 at 15:02

My BiL works for a company the 3D prints titanium. The reduced raw material volume outlays the complexity.