hammer and sickle vs emblem

hammer and sickle and emblem both are nouns.

Word	Noun	Adjective	Verb	Adverb
hammer and sickle	Yes	No	No	No
emblem	Yes	No	No	No

As nouns, emblem is a hypernym of hammer and sickle; that is, emblem is a word with a broader meaning than hammer and sickle:

Other hypernyms of hammer and sickle include allegory.

hammer and sickle (noun)	emblem (noun)
the emblem on the flag of the Soviet Union	special design or visual object representing a quality, type, group, etc.
	a visible symbol representing an abstract idea