no, i don't think that's the movie, because at the beginning of the expedition, there are more than 2 people; the bodies of their friends are being transformed by that thing; i don't remember for sure if really is a robot; i don't remember if it puts itself in their mutilated bodies, or if its just modifies and programs them to become killing machines
and i don't remember the man and woman being lovers from the begining

btw, thanks for the answer :)