Diffusion times are less than one hour. Water or oil quench is required. This type of cases present a significant distortion. Advantage of this method is the short time it requires to complete the diffusion, otherwise it should be avoided because of high distortion. In this process an electric current flow is induced in the workpiece to produce a haeting action.
Every electrical conductor carrying a current has a magnetic field surrounding the conductor.
Since the core wire is a dead-end circuit, the induced current cannot flow anyplace, so the net effect is heating of the wire. The resistance to current flow causes very rapid haeting of the core material. Heating occurs from the outside inward. Indusction hardening process includes water quench after the haeting process. The big advantage of this system is its speed and ability to confine haeting on small parts.