Damage mechanisms evolution of TiN/Ti multilayer films with different modulation periods in cyclic impact conditions

Abstract The evolution of cyclic impact damage mechanisms of TiN/Ti multilayer films were investigated in terms of microstructural transformation as the modulation period decreased sharp from micron-scale (1000 nm) to nano-scale (60nm). It was found that the ductile Ti phases reduced with decreasing modulation period, and the microstructures of films transformed from TiN/ TixNy /Ti to TiN/ TixNy (x>y). The cyclic impact results showed that both impact resistance and damage mechanisms of TiN/Ti multilayer films were strongly associated with modulation period. In the cyclic nano-impact conditions, the smaller modulation period of TiN/Ti film, the lower critical fracture load and higher fracture probability, thus worse impact resistance. Furthermore, the evolution of cyclic impact damage mechanisms of TiN/Ti multilayer films were revealed that in T1000 film, only few cracks were observed and the Ti interlayers could prevent cracks from extending deeper into film, resulting in slight fracture with small chippings. While there were many more cracks in T60 film and these cracks could easily across multilayers, leading to severe brittle spalling with multiple layers. It was demonstrated that with the microstructural transformation from TiN/ TixNy/Ti to TiN/ TixNy, a higher cracking probability was found in TiN/Ti films, and the crack propagation mode changed from horizontal along interface to vertical across multilayers.