Answer:
Case-hardening
Explanation:
Case-hardening
It is the process of hardening the surface of the metal object and allowing the metal which is deep inside to remain soft , hence , making a thin hard outer layer on the surface .
In case of iron which have low carbon content , the case - hardening is done by introducing high carbide or nitride content .
The process of case - hardening is done , in the final shaping process .
