Heat treatment is one of the most common methods of hardening steel. The steel is first heated and then rapidly cooled to harden it in order to change its structure. This process changes the microstructure of the steel and improves its mechanical properties.
Heat treatment can be divided into different processes, such as quenching, tempering and annealing. During quenching, the heated steel is immersed in a medium such as water or oil to ensure rapid cooling. This creates a martensitic structure that gives the steel a high degree of hardness. During tempering, the steel is then heated to a certain temperature and slowly cooled to achieve the desired combination of hardness and toughness. During tempering, the steel is first heated and then slowly cooled to allow the precipitation of carbides, which increase the hardness of the steel.
Work hardening is another method of steel hardening in which the steel is hardened by mechanical deformation. By rolling, forming or forging, the steel can improve its properties and become more resistant to wear.
During work hardening, the steel is deformed at room temperature, which changes its crystalline structure. The deformation creates dislocations in the crystal structure, which hinder the movement of the atoms and thus increase the strength of the steel. This process can be repeated several times to further increase the hardness of the steel.
Nitriding and carbonitriding:
Nitriding and carbonitriding are processes in which nitrogen is diffused into the surface of the steel. This forms a nitride layer that increases the hardness and wear resistance of the steel. This method is often used for steels that are exposed to high temperatures, pressures and chemical influences.
During nitriding, the steel is heated in a nitrogen atmosphere, causing nitrogen to penetrate the surface and react with the alloying elements present in the steel. This creates a hard nitride layer that protects the steel from wear. During carbonitriding, carbon is diffused into the surface of the steel in addition to the nitrogen, forming a thin layer of nitrides and carbides. This layer increases the hardness of the steel and improves its wear resistance.