Enhanced hardness and adhesion of TiAlN coatings via nanoscale compositional modulation

This study investigates the effect of compositional modulation on the structural and mechanical properties of TiAlN-based coatings deposited by reactive pulsed DC magnetron sputtering. Thin TiAl interlayers were introduced to promote nitridation and compositional continuity. X-ray diffraction revealed a cubic TiAlN structure with preferred (111) and (200) orientations, while cross-sectional FE-SEM showed finer and denser columnar grains in modulated coatings. The optimized configuration (225 nm TiAlN/25 nm TiAl, 2/2) achieved the highest hardness of 37.79 GPa, exceeding that of the TiAlN monolayer (34.23 GPa), attributed to grain refinement and stress modulation. Scratch testing showed improved adhesion in modulated coatings (Lc3 = 8.27 N), likely due to stress relaxation and enhanced interfacial integrity. Although direct microstructural confirmation by TEM was not available, the findings highlight compositional modulation as an effective strategy for tailoring the mechanical performance of TiAlN-based protective coatings.