At low ranks, they are useful, higher ranks not so. I am listing the artifacts that don't really help much for those higher levels.

Dark pyramid
Tachyon Cylinder

Perhaps make them more useful for higher levels? Allow artifact combining

Dark pyramid x10 -> 250 cloak artifact with same timer.
Tachyon x10 -> subspace seeker
Ancient crystal foci x3-x5 -> Crimson obelisks
Crimson obelisk x10 -> Mutagenic cartridges
Repair nanodrones x5-> Regenerative hull effect (10% hull per hour x 12 hours) (Only for non-disabled ships)
Shield restorer x5 -> Shield regen pulse (Shield recharge rate reduced to half for 72 hours) (Only for non-disabled ships)

Ultra long artifacts effect
Void shells x10 -> Same stats but lasts 1 week (7x duration)
and so on...

EDIT: Add a button beside stack-> Window with the choices of artifact combining.

I like that

/like

I think the way this can work efficiently (without too much effort) now is through new "Project" missions. These would be low energy cost missions where you can turn in X number of artifacts for a much better one at the end.

Please make them never ending. If not those artifacts introduced will be at a big premium.

two thumbs up for mission based upgrades