Nickel Copper and Copper Nickel are used for various applications. My experience (Though a long time ago) was with pipe, machinery shafts, valve bodies,and pumo casings.

Both materials have high thermal conductivity and are sluggish to weld. Unlike carbon steel that will "flow out" away from the arc slightly. The above alloys only "go where you put them". The SMAW rods I used were difficult to remove slag after welding.

GTAW welding requires the came skill as it does for other metals but a different "eye". Make sure the arc is melting the underlying base metal before adding filler metal. Do NOT depend on "melting it out" if you have a suspected defect. The need for gas coverage is greater with this material and also control of heat input. Problems with either will produce a bead with a very layer of grey oxid that sould be removed before additional layers are deposited. Cleanliness is VERY important on these metals. Porosity can easily be developed. Be careful for lack of fusion

Contamination from sulfur bearing materials must be controlled so use the proper metal removal tools.

Hope this helps a little.

Have a nice day

Gerald

Just to give you an information that may be useful. A well known nickel/copper alloy is Monel, containing 70% nickel and 30% copper.
Monel is a brand name that belonged to a company called International Nickel, which later changed its name to Huntington Alloys and now has changed again to Special Alloys, if I'm not wrong.
If you contact them, they'll give you every information you need on how to weld it.
Giovanni S. Crisi
Sao Paulo - Brazil