Nanocrystalline Hard Coatings within the Quasi-Binary System TiN-TiB2.

Ti-B-N films with a gradient in the chemical composition were deposited onto austenic stainless steel sheets by means of unbalanced DC magnetron co-sputtering using a segmented TiN/Tib2 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 of the coatings were measured using a depth-sensing nanoindenter. The composition of the films was found to lie close to the quasi-bianary section Ti-B-N. The grain size determined from TEM investigations range between 3 and 5 nm. Coatings consisted of a nanocrystalline fcc TiN phase (with boron atoms and oxygen impurities dissolved), and TiB2, TiB and B2O3. Microstructure as well as chemical composition on 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. 1998 Published by Elselvier Science Ltd. All right reserved.JRC.(IAM)-Institute For Advanced Material