It sounds as though you are talking about artifact creature tokens, not just artifact creatures. If this is the case, then your friend is correct. You know it is a token because some effect created them, rather than them existing as actual cards in the game.
110.5. Some effects put tokens onto the battlefield. A token is a marker used to represent any permanent that isn’t represented by a card.
Note that it is common to use things that look like cards as the markers to represent these tokens, but those things are not "cards" in the sense that a Mountain is a card; they don't go in your deck, etc.
Tokens work differently than cards when they die. While they do enter the graveyard, they immediately cease to exist before you have a chance to do anything such as casting Crypt Incursion. Therefore you cannot exile them from the graveyard.
110.5f A token that’s in a zone other than the battlefield ceases to exist. This is a state-based action; see rule 704.
Also note that even if the tokens did stay in the graveyard, it wouldn't matter, because Crypt Incursion specifically says "creature cards"; and as mentioned earlier, tokens are not cards.