hardened vs case-hardened

hardened and case-hardened both are adjectives.

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

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

Other synonyms of hardened include hard-boiled.

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