Rather than using a TIG torch, look into the EBM process (electron beam
melting):
http://www.youtube.com/watch?v=E7--ZWPVVdQ
As I see it, the big problem with using TIG instead is that you're not
heating up the spot directly under the electrode, you're heating up the
spot at the end of the _arc_. Generally the two are pretty much the
same, but magnetic fields can play havoc with where your arc wants to go.
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