Joseph Gwinn wrote:
There was a recent article in Aviation Week saying that GE was using
Electric Discharge Machining (EDM) to rough out turbojet blisks
(combined rotor and blades) from Inconel 718, which is almost as hard as
carbide. Apparently, GE got the idea in 2001 from the Chinese, who were
using EDM for drilling of such alloys.

After roughing, the blisks are cut to final form using electro-chemical
machining, and also polished.

GE calls the technology "Blue Arc", the blue being the color of the
proprietary working fluid.

Joe Gwinn


Aviation Week, 9 May 2011, page 16, "Submerged Results - Novel technique
speeds GE's blisk output", by Michael Mecham, The Inside Track (column).

I have not found this on the web; I assume it's behind a paywall.

There are patents, however. Search for "electric discharge" and
inconel. I found applications 2010/0301016 and 0301017 for instance.



EDM was shunned on aircraft parts because it was thought that
microcracks that would form in the cut which would cause failure of the
part. Now with the final finishing of the parts EDM is becoming the
choice for machining blades.

John