Ion carburizing

Claim 1

A process controlling the case carburizing of a ferrous workpiece under a vaccum in a chamber by the ion discharge of a carbon bearing gas comprising: (a) heating said workpiece by heating means independent of the operation of the flow discharge to a carburizing temperature whereat carburizing can occur and maintaining said temperature within said chamber principally by said heating means through the completion of step (e); (b) applying a DC current pulsed at constant periodically repeating intervals at a predetermined voltage between said workpiece as a cathode and said chamber as an anode in the presence of non-carbon bearing, ionizable gas at a predetermined vacuum to clean said workpiece; (c) reducing said DC pulsed current to a lower value while said non-carbon bearing gas is evacuated from said chamber and a gas consisting essentially of a carbon bearing gas is continuously introduced into said chamber through step (e); (d) after said non-carbon bearing gas has been substantially evacuated from said chamber in step c, increasing said voltage and said pulsed current to a predetermined wattage value correlated to the surface area of said workpiece to define a watt density power; and (e) simultaneously controlling said watt density power at said carburizing temperature and the continuous mass flow of said carbon bearing gas to establish a uniform carbon gradient profile within the case of said workpiece.