black lead vs graphite

black lead and graphite both are nouns.

Word	Noun	Adjective	Verb	Adverb
black lead	Yes	No	No	No
graphite	Yes	No	No	No

As nouns, black lead and graphite are synonyms defined as:

black lead and graphite: used as a lubricant and as a moderator in nuclear reactors

Other synonyms of black lead include plumbago.

black lead (noun)	graphite (noun)
used as a lubricant and as a moderator in nuclear reactors	used as a lubricant and as a moderator in nuclear reactors