MICROHARDNESS AND ADHESION OF TIB2 COATINGS PRODUCED BY DYNAMIC ION MIXING

The production at room temperature of adherent ceramic coatings on metallic substrates necessitates the improvement of conventional deposition techniques. Ion beam deposition processes using low energy ion beams have proved to be powerful methods for producing a wide variety of surface alloys. More recently, the use of high energy heavy ion beams in coating technology was investigated in order to improve the interface mixing effect and to control the structural state of the coating. We have deposited TiB2 alloy films on a tool steel via dynamic ion mixing (DIM) using either 320 keV Ar2+ ions or 320 keV Xe2+ ions. The depositing atom flux was obtained by sputtering a TiB2 target with an intense Ar+ ion beam of 1.2 keV delivered by a Kaufman-type ion source. The microstructure of the films was characterized by cross-sectional transmission electron microscopy. It is recognized that crystallization is induced by DIM and that the interface mixing has a beneficial influence on the adhesion performance of the coating. The relative increase in the Vickers microhardness of the coated tool steel substrate is of the order of 23%. The intrinsic hardness of the 1 μm TiB2 coatings on these substrates is estimated to about 2200 kgf mm-2 by application of the composite hardness model. © 1989.