helmet vs armor plating

helmet and armor plating both are nouns.

Word	Noun	Adjective	Verb	Adverb
helmet	Yes	No	No	No
armor plating	Yes	No	No	No

As nouns, armor plating is a hypernym of helmet; that is, armor plating is a word with a broader meaning than helmet:

helmet: armor plate that protects the head
armor plating: specially hardened steel plate used to protect fortifications or vehicles from enemy fire

Other hypernyms of helmet include armor plate, armour plate, plate armor, plate armour.

helmet (noun)	armor plating (noun)
a protective headgear made of hard material to resist blows	specially hardened steel plate used to protect fortifications or vehicles from enemy fire
armor plate that protects the head