case-hardened vs hardened

case-hardened and hardened both are adjectives.

Word	Noun	Adjective	Verb	Adverb
case-hardened	No	Yes	No	No
hardened	No	Yes	No	No

As adjectives, case-hardened and hardened are synonyms defined as:

Other synonyms of case-hardened include hard-boiled.

case-hardened (adjective)	hardened (adjective)
used of persons; emotionally hardened	made hard or flexible or resilient especially by heat treatment
	protected against attack (especially by nuclear weapons)
	made tough by habitual exposure
	converted to solid form (as concrete)
	used of persons; emotionally hardened