Pintakarkaistamiseen

Pintakarkaistaminen, also known as surface hardening or case hardening, is a heat treatment process used to improve the wear resistance and hardness of metal surfaces while maintaining the toughness of the core material. This is achieved by creating a harder, more brittle outer layer, or "case," on a component that is still relatively ductile in its interior.

The process typically involves heating the metal part to a specific temperature and then introducing a hardening element, such as carbon or nitrogen, into the surface. This diffusion of elements into the surface layer alters its chemical composition, making it susceptible to hardening when subsequently quenched in a suitable medium like oil or water. Different methods of introducing the hardening element exist, including carburizing, nitriding, and carbonitriding.

Carburizing involves diffusing carbon into the surface of low-carbon steel at elevated temperatures. Nitriding, on the other hand, diffuses nitrogen into the surface of steels containing nitride-forming elements, often at lower temperatures than carburizing. Carbonitriding combines both carbon and nitrogen diffusion.

The depth of the hardened case and the hardness achieved can be controlled by adjusting the process parameters, such as temperature, time, and the composition of the atmosphere or salt bath used. Pintakarkaistaminen is widely used in various industries, including automotive, aerospace, and manufacturing, for components like gears, shafts, bearings, and cutting tools, where surface durability is crucial for performance and longevity.