Sputter gas pressure and dc substrate bias effects on thick rf-diode sputtered films of Ti oxycarbides

Abstract

Films 1–10 μ thick have been prepared by rf-diode sputtering from targets of TiO0.5C0.5, TiO0.25C0.75, TiC, and TiN. These films were deposited on commercial, cobalt-bound, cemented, complex-carbide cutting-tool inserts. The inserts were sputter etched immediately prior to sputter coating. This etch was found to be essential for obtaining good bonding. The sputtered films were prepared under various conditions of argon gas pressure ranging from 3 to 56 μ and substrate bias from 0 to −200 V dc. The sputtered materials exhibited similar microstructures under the same deposition conditions. In general, it was found that higher pressures and less negative biasing gave a ’’cauliflower’’ structure. Reducing the pressure and increasing the negative substrate bias produced more columnar films with less porosity but at a reduced deposition rate for constant power input. X-ray diffraction analysis and Auger spectroscopic analysis of the TiO0.5C0.5 target and a sputter deposited film showed only a slight reduction in oxygen content of the material as a result of the sputtering process. The wear resistance of these films was evaluated by accelerated lathe cutting tests on hardened 4340 steel. The wear resistance was found comparable to good chemical-vapor-deposition (CVD) prepared coatings of TiC.