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This process produces steel where the soft layers are ~3 mm thick and the hard layers are ~0.25 mm thick. The layers could probably be thinner. My understanding

by twic 6y ago

This process produces steel where the soft layers are ~3 mm thick and the hard layers are ~0.25 mm thick. The layers could probably be thinner. My understanding is that the minimum layer thickness of this process is ~0.01 mm. The hard layers are created by rapid cooling; i'm not sure if the dynamics of the cooling process itself would create layers thicker than that. The steel used in the traditional Japanese sword-making referred to in the article has layers far thinner than that. If a sword is 7 mm thick at the hilt, and the steel has been folded 16 times, then the layers are 0.1 um (a tenth of a micron!) thick. Actual Damascus steel is something else entirely: https://en.wikipedia.org/wiki/Damascus_steel https://en.wikipedia.org/wiki/Damascus_steel But it's still a really cool process!

rbanffy 6y ago
I like the idea of using the laser for that - it'd allow for a more interesting 3D arrangement than folding and layering of different hardness materials. An obvious one is interlocking structures of hard/soft steel within the part.
- twic 6y ago
  That would be amazing. I'm not sure they can do that, though. From the article: > The team’s idea was to use the layer-by-layer printing process to manipulate the temperatures each layer experienced, alternating softer, more flexible layers with layers hardened by that precipitation process. While printing a cubic chunk of steel, they did this simply by turning the laser off for a couple minutes or so every few layers. The top layer would rapidly cool, converting to the desired crystalline form. Then, as additional layers were added on top, temperatures in the crystalline layer would cycle back up, inducing the precipitation of the nickel-titanium particles. The way they make the hard layers is by turning the laser off for a couple of minutes and letting the freshly-melted metal cool quickly. When you do that, everything that's hot and exposed will harden. Maybe you could use the laser to keep some areas of the metal hot while others harden? Or does the metal conduct too much heat to do that? Maybe you could build some areas up, then cool them slowly to make soft metal, then build up the gaps between those and cool them rapidly to make hard metal?
  - rbanffy 6y ago
    > Maybe you could use the laser to keep some areas of the metal hot while others harden? Or does the metal conduct too much heat to do that? Maybe you could build some areas up, then cool them slowly to make soft metal, then build up the gaps between those and cool them rapidly to make hard metal? That's pretty much what I was thinking

by twic 6y ago

rbanffy 6y ago

I like the idea of using the laser for that - it'd allow for a more interesting 3D arrangement than folding and layering of different hardness materials. An obvious one is interlocking structures of hard/soft steel within the part.

twic 6y ago
That would be amazing. I'm not sure they can do that, though. From the article: > The team’s idea was to use the layer-by-layer printing process to manipulate the temperatures each layer experienced, alternating softer, more flexible layers with layers hardened by that precipitation process. While printing a cubic chunk of steel, they did this simply by turning the laser off for a couple minutes or so every few layers. The top layer would rapidly cool, converting to the desired crystalline form. Then, as additional layers were added on top, temperatures in the crystalline layer would cycle back up, inducing the precipitation of the nickel-titanium particles. The way they make the hard layers is by turning the laser off for a couple of minutes and letting the freshly-melted metal cool quickly. When you do that, everything that's hot and exposed will harden. Maybe you could use the laser to keep some areas of the metal hot while others harden? Or does the metal conduct too much heat to do that? Maybe you could build some areas up, then cool them slowly to make soft metal, then build up the gaps between those and cool them rapidly to make hard metal?
- rbanffy 6y ago
  > Maybe you could use the laser to keep some areas of the metal hot while others harden? Or does the metal conduct too much heat to do that? Maybe you could build some areas up, then cool them slowly to make soft metal, then build up the gaps between those and cool them rapidly to make hard metal? That's pretty much what I was thinking