Actually the Naval combat force for boarding actions both commiting and defending, are called Arms Men. I am designing my current IG army along that idea.
You have different levels of Arms Men as well, you have your normal every day type that are somewhere between your normal IG trooper, to more specialized better armed ones that form personal security details as well as special operations types and these guys are all equiped more like stormtroopers. Also outside of the Armsmen you have the trusted crew who will be armed at times like these because an Imperial Warship of the smallest size is still going to have a minimum of 10-15k people on board.
Also you have the conscripted crew who serve in the lower decks doing the most dangerous work on the ship. These in an emergency may be armed with sticks and clubs and swords and sent to defend the ship as well.
So there is the actual basic break down of the troops.
"Oh it's you again...." *Bang
Inquistor Arkturus Palov as he banishes a daemon to the warp.