Monel metal vs nickel alloy

Monel metal and nickel alloy both are nouns.

Word	Noun	Adjective	Verb	Adverb
Monel metal	Yes	No	No	No
nickel alloy	Yes	No	No	No

As nouns, nickel alloy is a hypernym of Monel metal; that is, nickel alloy is a word with a broader meaning than Monel metal:

Monel metal: an alloy of nickel and copper and other metals (such as iron and/or manganese and/or aluminum)
nickel alloy: an alloy whose main constituent is nickel

Other hypernyms of Monel metal include nickel-base alloy.

Monel metal (noun)	nickel alloy (noun)
an alloy of nickel and copper and other metals (such as iron and/or manganese and/or aluminum)	an alloy whose main constituent is nickel