Carburization is a process of adding carbon to a material, typically a metal, to increase its hardness and strength. However, there are several synonyms for this term, including case hardening, carbonizing, and carburizing. Case hardening is the process of hardening a metal surface by infusing it with a hard outer layer, while carbonizing means adding carbon-rich material to a surface to increase its hardness. Carburizing is similar to carbonizing, but it specifically means adding carbon to a metal through heat treatment or chemical reaction. Other synonyms for carburization include carbo-nitriding, carbon diffusing, and carbon depletion. Each of these terms relates to increasing the carbon content of metal materials for various purposes.