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Powder metallurgy (wikipedia.org)
28 points by glassworm on Jan 2, 2019 | hide | past | favorite | 9 comments



A related method not mentioned in this article (or, in fact, many places at all) is iro3d[1]'s "selective powder deposition": a 3D printer effectively creates a mold out of sand, with empty spaces filled with a metal powder. After the "print", done in a crucible, is finished, an ingot of metal with a lower melting point is set on top & the whole thing baked in a kiln. The metal from top fills the space between the granules of powder and solidifies with nearly no shrinkage (as the object is mostly made of the powder, which never melts).

[1] http://iro3d.com/


3d printing is mentioned, under the additive processes.

It’s most likely not emphasized since the resulting product may have the size tolerances, but not the strength of the powdered metal. It’s still quite strong, but the strength is based off the “filler” material (similar to brazed parts), not the powdered metals (which acts more like rebar inside concrete).

I imagine this lack of strength (or lack of integration) of the original powdered material is what holds it (and other similar additive processes) back from being a well recognized PM process.


Over the years I’ve seen a couple of fascinating applications with powdered additive manufacturing. Living metal - powdered metal parts with bacteria ‘in the gaps’. Activated with heat their byproduct was lubricant. Great for bearing faces in mechanical equipment doing long distances in space.

The other was calcium powdered 3D printed parts that had a chemical forced through their porous mass, changing its chemical composition.


The specialist applications of powder metallurgy are awesome, not to mention the fact that lots of refractory metals can only be used with sintered powder (eg tungsten). It should also be pointed out that powder metallurgy parts have long been an important part of engineering (mostly sintered bronze bushings impregnated with grease), and have recently become hugely common as powder gears.

Manufacturing standard spur gears in particular has benefited HUGELY from powder metallurgy. You can use it to make exceptionally accurate and cheap extrudable shapes, and gears have traditionally been hugely expensive and wasteful because you have to cut out the teeth, harden, and final-cut. Powder metallurgy has created an important middle ground- exceptionally cheap medium-quality gears. Now instead of unhardened gears you will always get powder gears, which are better. In places where final-ground gears were overkill, powder gears have come in at acceptable quality and greatly reduced prices. Powder metallurgy is awesome!


> Now instead of unhardened gears you will always get powder gears, which are better.

Nope, now instead of unhardened gears you get powder gears which are even worse (but much cheaper than those good powder gears), but minimally better than plastic. My father is power tools' serviceman and since sintered gears became more common, there are MUCH more broken transmissions (but yeah, they are a little cheaper).


Turns out I already knew roughly how this process works from playing Factorio with Bob's/Angel's mods. It's relatively 'realistic', requiring crushing ores and sorting to get different breakdowns of products (And byproducts), further processing those products to get powders, recombining, sintering and pressing into pellets.


Or in a slightly more exciting format: https://www.youtube.com/watch?v=g7H0YFFV_oE



The single limiting factor against high production and good dimension advantage is Raw material production.




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