Graphite coating of tool steel by pressure spraying

This paper describes graphite coating of tool steel by pressure-spraying technology and the lubricating ability of such sprayed tool steel for metal-forming applications. This method introduces a dense graphite layer of approximately 1 μm into the surface of the tool steel by spraying graphite powder with pressurized nitrogen gas. Friction measurements indicate that the sprayed tool steel has more excellent lubricating ability and lubrication life compared with the case of conventional graphite coating. Ring compression and extrusion are performed at 773 K to make out the lubricating ability of the sprayed tool steel during large deformation processes. These results indicate that this method can control the seizure between tool and workpiece and consequently can improve the life of a metal-forming die and the surface accuracy of a workpiece.