blending vs gradation

blending and gradation both are nouns.

Word	Noun	Adjective	Verb	Adverb
blending	Yes	No	No	No
gradation	Yes	No	No	No

As nouns, gradation is a hypernym of blending; that is, gradation is a word with a broader meaning than blending:

blending: a gradation involving small or imperceptible differences between grades
gradation: the act of arranging in grades

Other hypernyms of blending include graduation.

blending (noun)	gradation (noun)
a gradation involving small or imperceptible differences between grades	the act of arranging in grades
the act of blending components together thoroughly	a degree of ablaut
	relative position in a graded series