PREPARATION OF CUBIC BORON-NITRIDE FILM BY CO2-LASER PHYSICAL VAPOR-DEPOSITION WITH SIMULTANEOUS NITROGEN ION SUPPLY

Hard cubic boron nitride (c-BN) rich films have been prepared by a newly developed CO2 laser physical vapour deposition process assisted by a simultaneous nitrogen ion supply. A high power CO2 laser of 200-1000 W was focused and irradiated onto the peripheral surface of a rotating sintered hexagonal boron nitride (h-BN) ring and the vapour was deposited on a substrate. N2 gas ionized in a Kaufman-type ion source was accelerated at a bias voltage of 0-2.0 kV and irradiated onto the substrate simultaneously with the laser evaporation process. The films were characterized by electron spectroscopy for chemical analysis, thin film X-ray diffraction, Auger electron spectroscopy, IR spectroscopy and scanning electron microscopy. Mechanical properties were also evaluated by Knoop hardness measurements, scratch tests and wear experiments. The composition ratio N:B of the films prepared from high purity 99% h-BN increased as the accelerating voltage increased and neared unity at about 1 kV. Cubic boron nitride (c-BN) was clearly identified at accelerating voltages over 0.5 kV. The higher the accelerating voltage was, the greater was the proportion of the cubic phase. The c-BN-rich films were found to have extremely high Knoop hardness of 3800-4600 kgf mm-2 and sufficient wear resistance against NiMo steel (SAE 4620). © 1990.