I am researching the process for blackening tantalum and am finding
it almost impossible. I am wondering if the process is similar to
colouring of titanium and therefore the results are the same i.e
surface oxidisation only, or if there is a process that yields a
hard wearing surface colour that will need minimal maintenance for
strength of colour. The tantalum portion of the design will be
taking all the ‘hard knocks’ and as the design is a wedding ring it
will obviously be worn everyday (or should be ;0).
Also any tips on fusing/welding would be helpful also…
Can anybody help me? Any would be greatly appreciated.
I am researching the process for blackening tantalum and am
finding it almost impossible. I am wondering if the process is
similar to colouring of titanium and therefore the results are the
same i.e surface oxidisation only, or if there is a process that
yields a hard wearing surface colour that will need minimal
maintenance for strength of colour.
Ti, Nb and Zr can be blackened with heat or molten salt baths (very
dangerous). I have not tried for a black on Ta as it is so nice and
dark already it is generally a good contrast for other metals.
The tantalum portion of the design will be taking all the 'hard
knocks' and as the design is a wedding ring it will obviously be
worn everyday (or should be ;0).
This is not a good idea, tantalum is very soft and is not a good
metal to be in high impact or abrasive situations.
Also any tips on fusing/welding would be helpful also....
Vacuum (E beam) welding, TIG welding in an argon glove box with less
than .1 ppm oxygen, very carefully rigged TIG or plasma welding with
auxiliary shielding gas supply devices. In other words not really
something a typical studio goldsmith can do. Tantalum is an amazing
“getter” of oxygen if there is any trace of oxygen present the hot
tantalum will absorb it and this ruins the weld. I think you may need
to do a reality check with your client as while a project like this
can possibly be done the cost will be astronomical to do it right or
the result will be mediocre at best.
I do not recall anyone trying to produce a black finish on Ta. We
get a pretty good charcoal grey/black on Niobium just with a red
heat and air cool. Do not know if Ta will do it or not. That said
the blackened Nb is very hard and wears well. It is not permanent!
It is only a coating. Black oxides as a a wearing surface are bad
choice for a wedding ring. Anything you do to the surface will wear
off. period. As to your other questions, here is a good place to
start your research…
Tantalum-Niobium International Study Center
Chaussee de Louvain 490,
1380 Lasne, Belgium
Tantalum will anodize exactly as does titanium, but it gives a much
more beautiful color effect. Same colors, but much more vivid than
titanium.
(it’s a visual effect, so I can’t explain it in a way that’ll make
sense, but do a color test strip with Ta, and then another one with
Ti. Lay them side by side, and you’ll see the difference I’m talking
about.)
Unfortunately, neither metal does “black” well, unless you burn
them, which is likely to make them brittle.
On both metals, the color is a surface effect that’s reasonably
fragile, and certainly not something I’d use for the hard wearing
section of a wedding ring.
I’d look more at either tungsten carbide, or black ceramic for
something like that.