Effect of Si content on microstructural evolution and superhardness effect of TiN/CrAlSiN nanomultilayered films

• The TiN/CrAlSiN nanomultilayered films with different Si content were synthesized.
• The effect of Si content on microstructure and superhardness effect was studied.
• The columnar crystal structure can be effectively refined with the low Si content.
• The nanomultilayered film presents superhardness effect with Si:CrAl ratio of 4:21.
• High Si leads to amorphization of CrAlSiN and decrease of mechanical properties.

Through introducing the CrAlSiN modulation layers consisted of CrAlN and SiNx phases, a series of TiN/CrAlSiN nanomultilayered films with different Si content were synthesized by reactive magnetron sputtering. The effect of Si content on microstructural evolution and superhardness effect of TiN/CrAlSiN nanomultilayered film was investigated by XRD, HRTEM and nanoindentation techniques. When inserted by CrAlSiN nano-layers with Si:CrAl ratio less than 4:21, TiN layers can force CrAlSiN layers to transform into fcc structure and grow epitaxially with them, leading to appearance of the superhardness effect. The columnar crystal structure of TiN/CrAlSiN nanomultilayered film can be effectively refined by insertion of the CrAlSiN layers due to thermodynamic incompatibility of CrAlN and SiNx. As the Si content further increases, the amount of amorphous SiNx phase increases, which makes the CrAlSiN layers present amorphous feature and blocks the epitaxial growth structure within the TiN/CrAlSiN nanomultilayered film, resulting in the decrease of hardness and elastic modulus.