Everything begins with neutral hardening. Also known as "quench and temper," this process improves the strength and toughness of medium- to high-carbon steels evenly through the entire part. This result is achieved by heating parts above the phase-transformation temperature for a set period of time to change their crystalline structure from body-centered cubic to face-centered cubic. The part is then plunged rapidly into a quenchant to change the structure to a tetragonal arrangement, thus giving it a remarkably high hardness. Oil and water are both common quenchants, with oil being the less aggressive of the two. The choice to use water or oil is determined by the material being used and the desired metallurgical properties of the finished part. After quenching, parts must be reheated (i.e., tempered or drawn down) to the desired hardness to create a tempered martensitic microstructure. Tempering of quenched steel is a critical final process to relieve microstructural stresses in the part and prevent distortion / cracking while simultaneously improving toughness and ductility. After the tempering process, the part is tested for hardness using the Rockwell scale, and several material properties can be extrapolated from that measurement.

Carburizing is a case-hardening process to improve surface hardness for low-carbon steels. This is achieved by adding free carbon to the processing atmosphere and allowing it to diffuse into the surface of the part. The carbon-infused surface layer has superior wear capabilities and high Rockwell hardness specifications.

Carbonitriding is a case-hardening process similar to carburizing. It is generally performed at lower temperatures with the addition of nitrogen via ammonia gas. This process increases wear resistance and surface hardness through the creation of a hardened surface layer, which is diffused at these lower temperatures. The diffusion of nitrogen at these temperatures provides a more resistant case and increases the hardenability of low-carbon steels. Carbonitriding is well suited for parts that require wear-resistant properties with reduced distortion. Case depths for carbonitriding are generally much lower than those of carburized parts, varying from a low of 0.003 to 0.030 inches (0.08mm to 0.76mm). Parts are commonly quenched in oil and tempered at low temperatures to increase toughness and reduce brittleness.