disaster vs hard knocks

disaster and hard knocks both are nouns.

Word	Noun	Adjective	Verb	Adverb
disaster	Yes	No	No	No
hard knocks	Yes	No	No	No

As nouns, hard knocks is a hypernym of disaster; that is, hard knocks is a word with a broader meaning than disaster:

Other hypernyms of disaster include adversity, hardship.

disaster (noun)	hard knocks (noun)
an act that has disastrous consequences	a state of misfortune or affliction
an event resulting in great loss and misfortune
a state of extreme (usually irremediable) ruin and misfortune