Sciencemadness Discussion Board

Forgability of chromium

DoctorOfPhilosophy - 28-6-2016 at 12:31

I'm trying to forge a sputtering target out of chromium metal, I melt chromium powder into blobs and then hammer them on an anvil. The problem is they don't seem to be forgeable at all, when I hit them reasonably hard they don't deform, when I hit them really hard they shatter. All of this is happening at almost the melting point of chromium (I'm heating it with a TIG welding torch until it's just starting to melt).

Anyone know what's going on?

Fulmen - 28-6-2016 at 14:27

Nitrogen embrittlement perhaps? Or are you using an inert blanket?
https://en.wikipedia.org/wiki/Chromium#Passivation

DoctorOfPhilosophy - 28-6-2016 at 16:46

Looks like that might be it. I used argon for the initial melt but the metal dust was not compressed prior to melting. Also no protective gas was used during forging, another pathway for N2 to enter.

Can I remove the nitrogen and reuse the chromium metal?

[Edited on 29-6-2016 by DoctorOfPhilosophy]

Fulmen - 28-6-2016 at 17:28

Could be. According to wiki chromium nitride decomposes at 1770C, so prolonged heating could release the nitrogen. Would probably take some time though.

https://en.wikipedia.org/wiki/Chromium_nitride


Fleaker - 4-7-2016 at 06:44

Chromium is brittle. All the sputtering targets I used to get in of pure Cr I beat up with a hammer before further pulverizing.

If you're going to make a sputtering target out of it, best to vacuum induction cast it and then EDM it to size.

DoctorOfPhilosophy - 5-7-2016 at 02:43

I already destroyed half the machine shop trying to shape chromium using conventional tools. I'm just going to grind it to the correct size using an angle grinder and later a dremel to get the shape right.

Fleaker - 6-7-2016 at 07:21

Beware the dust!

DoctorOfPhilosophy - 9-7-2016 at 19:44

Right, another chemist already warned me about that. In the end my project partner ordered a huge slab of chromium. It appears to have machining marks on it, so I wonder what parameters they used to make that work.

Bezaleel - 18-7-2016 at 08:30

Quote: Originally posted by Fleaker  
Beware the dust!

I'm sorry if this is a silly question, but is this a general remark, or is chromium dust particularly harmful? I would guess it's just in the +0 charge state, so from that perspective no more harmful than other metal dust.

Antiswat - 22-7-2016 at 01:08

i think chromium hype derives from the nefarious chromium six (hexavalent) which is produced in smaller amounts from welding (tig-wig especially iirc) although they have recently stepped down the toxicity opinion regarding hexavalent chromium, potential carcinogen is main concern i'd guess, so be very careful with ethanol too, another carcinogen.

maybe look up some "how its made" videos of chromium or the like? there has to be videos around of it, electrodeposition onto metals that you can easily dissolve with chemicals would be a way around getting violent with the chrome, although conc H2SO4 and CrO3 seems to be the way to electroplate chromium, quite different from many other metals where you can oftenly bypass having the metal in its ionic form in the electrolyte from start

Fleaker - 15-8-2016 at 12:35

Machining Cr probably gives mostly Cr2O3 fume but perhaps some higher chromium oxides can form.