Preparation,microstructure and mechanical properties of Ti-B-N nanocomposite coatings

Ti-B-N nanocomposite coatings with different B contents were deposited on Si(100) and high speed steel(W18Cr4V) substrates by reactive magnetron sputtering.The microstructures of the coatings were characterized by X-ray diffraction(XRD) and high-resolution transmission electron microscopy(HRTEM).Meanwhile the nanohardness and elastic modulus values were measured by nano-indention method.It is indicated that Ti-B-N nanocomposite coatings can be prepared by changing the power of TiB₂ targets and Ti targets.The deposited Ti-B-N coatings mainly consist of TiN nanocrystals.With the B content increasing,the sizes of TiN nanocrystals become smaller,and the amorphous component increases.When the B content is very high,the sizes of TiB₂ nanocrystalline phase in the Ti-B-N coatings are very small and the coatings' properties are poor.When the TiN grain size is about 5nm,the Ti-B-N coatings have the best mechanical properties,with the nanohardness of 32.7GPa and the elastic modulus of 350.3GPa.