PROCESS AND PROPERTIES OF CRN COATING DEPOSITED ON PLASMA-NITRIDED HIGH-SPEED STEEL

The hard-coating processes of plasma nitriding and cathode are plasma deposition technology were applied to an AISI M2 high-speed steel subs trate. A nitrided layer was first formed on the surface of the substra te by plasma nitriding under various nitrogen partial pressures. Then a CrN hard coating was deposited on top of the nitrided steel to form a composite layer structure. Nitrogen contents of the nitrided layers were measured by Auger electron spectroscopy. X-ray diffraction analys is, SEM and optical microscopy were used to characterize the microstru cture of the nitrided layer and the CrN film. It was found that the ni trogen partial pressure played a major role in the formation of the ni trided layer and its nitrogen content. The surface hardness of the spe cimens with the CrN-coated composite layer was significantly increased . The composite coating also resulted in better wear resistance and a lower friction coefficient.