High density of stacking faults strengthened TaN/TiN multilayer

Abstract

Multilayer coatings with individual layer thickness on the nanoscale exhibit superior mechanical properties because of their high interface density. However, compared to artificial phase interfaces, planar defects like twin and stacking faults (SFs) are hardly investigated in ceramic multilayer systems. We choose to combine the group VB transition metal nitride (TMN) TaN with its extremely low stacking faults energy (SFE) and TiN to form a superlattice (SL). TiN/TaN multilayers with a bilayer period (Λ) from 8 nm to 100 nm were prepared by dc magnetron sputtering. These as-deposited films show a peak hardness 36 ± 2.4 GPa at Λ=20 nm. The extensive high-resolution transmission electron microscopy (HRTEM) observations reveal that the dissociation of full dislocations results in the network of SFs and the formation of Lomer-Cottrell lock arrays inside the TaN layer. Meanwhile, further dislocation analysis indicated the Shockley partials cross slip at the interface. These findings provide us with a new perspective for designing TMN multilayers with planar defects.