bad luck vs disaster

bad luck and disaster both are nouns.

Word	Noun	Adjective	Verb	Adverb
bad luck	Yes	No	No	No
disaster	Yes	No	No	No

As nouns, disaster is a hyponym of bad luck; that is, disaster is a word with a more specific, narrower meaning than bad luck:

bad luck: unnecessary and unforeseen trouble resulting from an unfortunate event
disaster: an event resulting in great loss and misfortune

bad luck (noun)	disaster (noun)
unnecessary and unforeseen trouble resulting from an unfortunate event	an act that has disastrous consequences
an unpredictable outcome that is unfortunate	an event resulting in great loss and misfortune
an unfortunate state resulting from unfavorable outcomes	a state of extreme (usually irremediable) ruin and misfortune