THE EFFECT OF NITROGEN GAS FLOW RATE ON THE PROPERTIES OF TiN-COATED HIGH-SPEED STEEL (HSS) USING CATHODIC ARC EVAPORATION PHYSICAL VAPOR DEPOSITION (PVD) TECHNIQUE

Abstract

Cathodic arc evaporation (CAE) is a widely-used technique for generating highly ionized plasma from which hard and wear resistant physical vapor deposition (PVD) coatings can be deposited. A major drawback of this technique is the emission of micrometer-sized droplets of cathode material from the arc spot, which are commonly referred to as "macroparticles." In present study, titanium nitride ( TiN ) coatings on high-speed steel (HSS) coupons were produced with a cathodic arc evaporation technique. We studied and discussed the effect of various nitrogen gas flow rates on microstructural and mechanical properties of TiN -coated HSS coupons. The coating properties investigated in this work included the surface morphology, thickness of deposited coating, adhesion between the coating and substrate, coating composition, coating crystallography, hardness and surface characterization using a field emission scanning electron microscope (FE-SEM) with energy dispersive X-ray (EDX), X-ray diffraction (XRD) with glazing incidence angle (GIA) technique, scratch tester, hardness testing machine, surface roughness tester, and atomic force microscope (AFM). An increase in the nitrogen gas flow rate showed decrease in the formation of macro-droplets in CAE PVD technique. During XRD-GIA studies, it was observed that by increasing the nitrogen gas flow rate, the main peak [1,1,1] shifted toward the lower angular position. Surface roughness decreased with an increase in nitrogen gas flow rate but was higher than the uncoated polished sample. Microhardness of TiN -coated HSS coupons showed more than two times increase in hardness than the uncoated one. Scratch tester results showed good adhesion between the coating material and substrate. Considerable improvement in the properties of TiN -deposited thin films was achieved by the strict control of all operational steps.