Induction Hardening

Induction hardening

Induction hardening is a case hardening process used to increase wear resistance, surface hardness and fatigue life through creation of a hardened surface layer while maintaining an unaffected core microstructure. It is an electromagnetic process using a copper inductor coil, which is fed a current at a specific frequency and power level.

The parts to be heat treated are placed inside a copper coil and then heated above their transformation temperature by applying an alternating current to the coil. The alternating current in the coil induces an alternating magnetic field within the work piece which causes the outer surface of the part to heat to a temperature above the transformation range. The coil runs along the length of the part to be hardened and is quenched immediately using polymer or oil that is sprayed onto the workpiece. The hardened case differs from that of a carburized case in that the hardness is uniform for the entire depth.

Induction hardening is used to increase the mechanical properties of ferrous components in a specific area. Typical applications are powertrains, suspension parts, engine components and stampings. Induction hardening is excellent at repairing warranty claims / field failures. The primary benefits are improvements in strength, fatigue and wear resistance in a localised area without having to redesign the component.


Induction hardening is favoured for components that are subjected to heavy loading. Induction imparts a high surface hardness with a deep case capable of handling extremely high loads. Fatigue strength is increased by the development of a soft core surrounded by an extremely tough outer layer. These properties are desirable for parts that experience torsional loading and surfaces that experience impact forces. Induction processing is performed one part at a time allowing for very predictable dimensional movement from part to part.


Induction hardening is a heat treatment process carried out to enhance the mechanical properties in a localised area of a ferrous component. The resultant hardened area improves the wear and fatigue resistances along with strength characteristics.

Typical applications of induction hardening include gears, shafts, axles, cam lobes, stampings, and spindles, mostly symmetrical parts. Induction hardening is used to strengthen a specific area of a part. Induction hardening can be applied to a wide range of steels and irons.

Some are mentioned below:

  • Carbon steels
  • Alloy steels
  • Stainless steels(martensitic)
  • Powder metal
  • Cast iron
  • Gray iron
  • Ductile iron
  • Malleable iron