There's no such thing as "too soon." You just have to figure out how to integrate it in a way that is suitable to you.

If it's too strong for the party, dial it back. Nerf the item, and have them "unlock" powers and abilities and have it grow over time.

Or you can weave it in and out of the party's story, like have them find it, get to wield it and feel badass, then turn it over to a dwarvish church. They get to enjoy it, feel badass, and it goes away before it ruins too much. While they have it, maybe it is too powerful, but who cares? Let them have that feeling of being overpowered, to show off the might of this artifact. And sometime later, the church is attacked/destroyed, the item stolen, and they have to keep it, and hang on to it until they can find somewhere else for it to go for safekeeping (and if you let them level up a few times in the process, it'll slowly become more suitable to them, and less "crazy op").

You can go a step further by seeing out relatively-equivalent items for the rest of the party. Maybe they each get an artifact that ties into some over-arcing plot (the Heroes of The Planes once saved the day, and each wielded a legendary weapon, allowing you to customize things like a "Bow of the Elven Hunters" or "Staff of the Halfling Mage" or whatever for your party; or they could all be dwarf themed, each piece from a different Dwarvish Lord; or you could just drop in enough extra magic items that a few pieces put together on one player are roughly equivalent to the Axe on another). Then just play a high-powered game. Takes some effort to balance, but once you get a feel for how much more the party can take because of their gear, you just alter the challenges they face to keep things competitive.