THE EFFECTS OF METALLIC INTERLAYER FORMATION ON THE ADHESION PROPERTIES OF PACVD - TiN FILMS ON TOOL STEEL

The adhesion of PACVD - TiN films on tool steel (AISI M2) has been investigated as a function of interfacial chemistry and the metallic interlayer formation between TiN films and substrate steel. Prior to TiN deposition, thin metallic interlayers such as Ti, Cr, Cu films were deposited on a steel substrate with thickness range of 200 - 2000 A by Magnetron sputtering. TiN films were deposited by RF Glow Discharge PACVD technique using the gaseous mixture of TiCl4, N2, H2 and Ar at 520 °C. The adhesion strength of TiN films was investigated by Scratch Adhesion Tester (REVETEST model) with a diamond stylus. The critical load in adhesion test was about 35 N in the case of no metallic interlayer and it was increased up to 60 N in the presence of 200 Å thick Ti interlayer. The interfacial composition profile was investigated by Auger depth profile. The experimental results indicated that a thin Ti intermediate layer ([MATH] 600 Å) could increase the adhesion and the critical normal force in the scratch adhesion test was up to 60 N. In the case of Ti interlayer formation, the oxygen in the interfacial region plays an important role on the adhesion of TiN coating by the formation of a Ti(ON) type phase