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 less hard metal.
Applications
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 to 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.