Nanocrystalline hard coatings within the quasi-binary system TiN-TiB2

Ti-B-N films with a gradient in the chemical composition were deposited onto austenitic stainless steel sheets by means of unbalanced DC magnetron co-sputtering using a segmented TiN/Tib(2) target. Film microstructure was characterized by means of electron-probe microanalysis (EPMA), transmission electron microscopy (TEM), electron energy-loss spectroscopy (EELS), and X-ray diffraction (XRD) as well as glancing angle X-ray diffraction (GAXRD). The mechanical properties oft he coatings were measured using a depth-sensing nanoindenter. The composition of the films was found to lie close to the quasi-binary section TiN-TiB2 within the ternary system Ti-B-N. The grain size determined from TEM investigations range between 3 and 5 nm. Coatings consisted of a nanocrystalline fee TiN phase (with boron atoms and oxygen impurities dissolved), and TiB2, TiB and B2O3. Microstructure as well as chemical composition of the films were not influenced significantly by the deposition parameters used in this investigation. Contrary, the mechanical properties were strongly influenced varying the ion bombardment. Hardness values exceeding 50 GPa and elastic moduli close to 500 GPa were obtained. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.