Types of Metal Hardening Processes

by Corr S. Pondent; Updated September 26, 2017

Metal hardening is a process that makes a metal stronger. For instance, a metal like stainless steel that finds a lot everyday use can stand wear better by going through a process of hardening. There are different types of metal-hardening processes, such as heat treatment. Which method to use depends on the type of metal that will undergo the process, as well as the level of hardness required.

How the Processes Work

The hardening processes typically change the mechanical properties of the metal. The piece becomes harder to wear down and also acquires strength and becomes difficult to deform it. The metal-hardening process could also alter some of the metal’s physical properties, including its magnetic properties.

Surface Hardening

Surface hardening of metals increases their resistance to wear and also makes them stronger. Surface hardening involves changing, on its surface zone, a metal’s chemical composition and its micro-structure. Thermal and chemical surface-hardening methods do this using heat-based and chemical-based processes. Laser heat treatment is a more recent surface-hardening technique.

Quench Hardening

Quench hardening is a form of thermal hardening used on steel and cast-iron metals. This process involves heating the metal to a certain temperature, depending on the percentage of carbon content in the steel or iron. The metal is held at this temperature for a certain period of time. This process transform’s the metal’s lattice structure and makes it more resistant. After this quenching process, the metal is tempered.


Metal-hardening processes have to be done properly, or could result in problems. If the quenching is not done uniformly, for instance, it could cause the metal to warp. And if the quenching process is too severe, it could change the dimensions of the steel. Another problem that could arise is that the metal could crack. This might happen if steel is not tempered immediately following the quenching process. Also, if the quenching is not strong enough, the metal may not harden.