hardened vs toughened

hardened and toughened both are adjectives.

Word	Noun	Adjective	Verb	Adverb
hardened	No	Yes	No	No
toughened	No	Yes	No	No

As adjectives, hardened and toughened are synonyms defined as:

hardened and toughened: made hard or flexible or resilient especially by heat treatment

Other synonyms of hardened include tempered, treated.

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