TRIBOLOGICAL PROPERTIES OF C-BN COATINGS IN VACUUM AT HIGH-TEMPERATURE

Thin cubic boron nitride(c-BN) coatings were deposited on a silicon wafer by activated reactive evaporation with a gas activation nozzle. The micro Vickers hardness of a c-BN coating with 0.4 mum thickness was about 4000 kg mm-2. The tribological properties of the c-BN coatings were studied by the ring-on-disk type tribotester. The friction coefficient of the c-BN coatings in sliding contact with stainless steel was about 0.35 in air. In a vacuum of pressure 1.7 x 10(-3) Pa at 673 K, the friction coefficient of the c-BN coatings in sliding contact with stainless steel was high at the initial stage, but then rapidly reduced to a very small value (less than 0.05) within 2 min, and reached the lowest value of 0.009 at the stable stage. The wear resistance of the c-BN coatings was also excellent. The rubbed surface of the c-BN coatings was measured and observed by the roughness tester and the scanning electron microscope respectively, but a clear wear trace was not found.