COMBINED PLASMA NITRIDING AND PVD TREATMENTS

A duplex surface engineering technique has been developed in an attempt to successfully apply thin hard ceramic coatings on commonly used low alloy steels. The low alloy steel (En40B) was first plasma nitrided so as to produce a relatively thick and strong subsurface layer, and then deposited with such ceramic coatings as TiN, CrN and (TiAl) by plasma assisted PVD. A series experiments have been carried out to investigate the structures and properties of the duplex treated steel. It is shown that such combined plasma nitriding and PVD treatments can produce a variety of coating/substrate interface structures and tribological properties. By proper process control, the resultant ceramic coating/nitrided steel composite possesses superior tribological performance over the individually plasma nitrided or PVD coated steel.