Structural and nano-mechanical characterization of TiN / Ti1−xAlxN multilayered thin films

Nanostructured multilayers have high interface area densities along with other factors such as periodicity, single layer thickness, sharpness, in general lead to improved mechanical properties. In this study, we have selected a combination of two metallic hard materials, such as cubic TiN and metastable cubic TiAIN sub-layers to synthesize a periodic multilayer thin films. Advantage of TiAIN as a sub-layer is the stability against oxidation due to the formation of dense Al₂O₃, which prevents further oxidation. These periodic TiN/TiAIN multilayers were synthesized by reactive magnetron co-sputtering technique on SS 304 LN substrates with TiN as a starting sub-layer and TiAIN as next with bi-layer thicknesses 7 nm to 60 nm. GIXRD results confirm the formation of metastable TiAIN with NaCl structure which is similar to TiN with a shift in the peak position. The individual layers were resolved by X-TEM and Secondary Ion Mass Spectroscopy to understand the architecture. Depth sensing nanoindentation was used to study the surface hardness which clearly explains the reverse Hall-Petch relationship (change in the periodicity). The maximum surface hardness of 34 GPa was obtained for a bi-layer thickness of 30 nm.