Effects of nitrogen content on nanostructure evolution, mechanical behaviors and thermal stability in Ti-B-N thin films

摘要

Several thin films of Ti-B-N with different N contents were deposited at 500 degrees C on Si (100) substrate by reactive unbalanced dc magnetron sputtering, followed by vacuum annealed at 600, 800 and 1000 degrees C, respectively. The effect of nitrogen content on microstructure, mechanical behaviors and thermal stability was investigated by X-ray diffraction (XRD), plan-view high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) and microindentation methods. The results indicated that nitrogen content had a great effect on phase configuration, microstructure and the corresponding mechanical behaviors. An amorphous (a-) Ti-TiB2 compound thin film which consists of Ti and TiB2 with a low hardness value was formed without nitrogen doped. Addition of small amount of nitrogen (10 at.% N in this study) produced nanocomposite nanocrystalline (nc-) Ti(N)/a-TiB2 thin films by way of activating phase segregation. Increasing nitrogen content accelerated further segregation of phase, accompanied with formation of nanocomposite nc-TiN/a-TiB2 thin films and fast increase of microhardness value. A maximum microhardness value of about 52 GPa was obtained at TiB0.52N0.63. Further increase of N content accelerated formation of BN bonding, followed by formation of nc-TiN/a-TiB2/a-BN thin films and fast decrease of microhardness value. The residual stress was not consistent with the microhardness, and showed linear increase with increasing N content. The thermal stability of Ti-B-N thin films strongly depended on microstructure and phase configuration. A high thermal stability usually occurred at an optimum composition which had a high microhardness value. (c) 2006 Elsevier B.V. All rights reserved.