Reactive sputtering in the ABS TM system

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The cathodic arc and unbalanced magnetron (UBM) sputtering processes have been combined into one unit called the ABS TM coating system, the very first of which was installed at BIRL. The arc process is usually used for the substrate sputter etching step, and shutters remain in front of the cathodes to intercept macroparticles. A conventional argon sputter etch is also available, but it takes approximately 100 min to heat a full load of substrates to 300 °C, against 15 min for the arc etch. The longer argon etch roughens the substrate surface, whereas the shorter arc etch can actually lead to a reduction in surface roughness. The UBM process with its high degree of ion bombardment is used for reactive deposition of the coatings. TiN and Ti 0.5Al 0.5N coatings produced in the ABS TM system have excellent hardness and scratch test critical load values. The hardnesses for TiN and Ti 0.5Al 0.5N coatings are 2200 and 2250 kgf mm -2 respectively, and the critical load for TiN on M2 tool steel is 50–60 N for a 2.0 μm thick film. For a 3.0 μm thick Ti 0.5Al 0.5N coating on tool steel, the critical load is 60 N, and on cemented carbide it is greater than 100 N. Field trials with Ti 0.5Al 0.5N coated saw blades and end mills show a 2–3 times improvement in performance compared with TiN coated tools. Cross-sectional transmission electron microscopy shows that the structure of a Ti 0.5Al 0.5N coating on steel is columnar and that it is fully dense.