Not that I'm aware of. Both Piper and Dogmeat have taken a knee more times than I care to count but neither has died yet. The real threat to companions is them disappearing off the face of the earth as I've lost the pair of them and don't have a clue where they might be.
Well I mean if I bump into her again and she's forgiven me for showering her with fire, sure. I was making good progress on our companionship (she apparently gets off on watching locks being picked) and got a couple of *~*touching conversations*~* before the trout hit the fan.