COMPARISON OF TIALN COATINGS GROWN BY UNBALANCED MAGNETRON AND ARC BOND SPUTTERING TECHNIQUES

Basic research has shown that, during the etching stage of the cathodi c-arc process, metal atoms of the coating material become embedded in the surface of the substrate to be coated. If 1200-eV Ti ions are used for etching, the penetration depth may be as great as 1500 angstrom. Paralleling this, more recent results reveal that an unbalanced magnet ron can be used to produce dense, droplet-free TiN layers in an exactl y reproducible form. Hence, when the arc-mode etching process is combi ned with unbalanced magnetron-mode coating, the resulting coating can be expected to have excellent properties. The technical implementation of this combined technique is known as ''arc bond sputtering,'' and i s known commercially as ABS(TM). This article describes how the proces s of producing TiAl-nitride layers is used to demonstrate the advantag es of metal-ion pretreatment on the adhesive strength of Ti0.5Al0.5N l ayers applied to high-speed steel and cemented-carbide substrates. The adhesive-strength criteria are the L(C) and the Rockwell indentation test. The result of this study indicates that the Ti-ion pretreatment renders the measured adhesive-strength values for the subsequent films much less sensitive to uncontrolled variations of the coating-process parameters. It is also shown how the formation of TiAl droplets durin g the arc-based etching process can be reduced through the use of shut ters.