Temperature dependence of structure and mechanical properties of Ti–Si–N coatings

Characterization of structure and mechanical properties of Ti–Si–N coatings deposited by a high-density plasma assisted vapor deposition technique at ∼250 °C was carried out and compared to Ti–Si–N coatings deposited at ∼700 °C. The nanoscale structure of Ti–Si–N coatings was probed by combining transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS). The structural characterizations showed that the present Ti–Si–N coatings consists of nanocolumnar B1-TiN grains interdispersed within an amorphous silicon nitride (a-Si:N) matrix, independent of the deposition temperature. Significant Ti atom dissolution within the a-Si:N matrix was observed, and increasing the deposition temperature from ∼250 to ∼700 °C decreases the Ti dissolution limit. The influence of the extent of the TiN/a-Si:N phase separation on the mechanical properties of Ti–Si–N coatings is probed by instrumented nanoindentation. The extent of phase separation was found to significantly influence the mechanical properties, with the hardness of Ti–Si–N coating deposited at ∼700 °C reaching ∼40 GPa. The present results illustrate the sensitivity of mechanical properties of ceramic nanocomposite coatings on the detailed nanoscale structure.