FORMATION AND CHARACTERIZATION OF CUBIC BORON-NITRIDE FILMS BY AN ARC-LIKE PLASMA-ENHANCED ION PLATING METHOD

Thin films of cubic boron nitride (cBN) were synthesized by means of an arc-like plasma-enhanced ion plating process. The infrared spectra of the deposited films showed strong absorption at around 1080 cm-1, indicating a cubic structure. The electron diffraction patterns also showed a continuous ring type, indicating a polycrystalline zincblende structure. A transmission electron micrograph of cBN films deposited in this process showed that the microstructure consists of fine grains of 5 to 10 nm. The cBN films deposited here generally had a high compressive stress of 4 GPa, which strongly reduced their adhesion to the substrate. It was found that the internal stress of cBN films was greatly reduced if hard amorphous BN (referred to as iBN, where the "i" indicates an ion-assisted process) was used as a buffer layer between cBN and the substrate. In order to improve the properties of hard coatings, sequenced layers with the combination of cBN/iBN/Ti were prepared to a final thickness of around 3-mu-m. These multilayered coatings are discussed in this report from the point of view of the relaxation of the internal stress in films.