Hardening is a metallurgical metalworking process used to increase the hardness of a metal. The hardness of a metal is directly proportional to the uniaxial yield stress at the location of the imposed strain. A harder metal will have a higher resistance to plastic deformation than a less hard metal.
Material hardening is required for many applications:
- Construction materials – High strength reduces the need for material thickness which generally saves weight and cost.
- Machine cutting tools (drill bits, taps, lathe tools) need be much harder than the material they are operating on in order to be effective.
- Knife blades – a high hardness blade keeps a sharp edge.
Bearings – necessary to have a very hard surface that will withstand continued stresses.
- Armor plating – High strength is extremely important both for bulletproof plates and for heavy-duty containers for mining and construction.
- Anti-fatigue – (Martensitic) case hardening can drastically improve the service life of mechanical components with repeated loading/unloading, such as axles and cogs.