Carburizing is a heat treatment process used to harden the surface of steel. During this process, the steel is heated in the presence of a carbon-rich material, allowing carbon atoms to diffuse into the surface. This increases the carbon content at the surface, enhancing hardness and wear resistance. After carburizing, the steel is usually quenched, which involves rapidly cooling it to lock in the carbon. This results in a hard outer layer while maintaining a softer, tougher core. Carburizing is commonly used in manufacturing components like gears and shafts, where durability is essential.