Nanotwinned transition metal nitride coating with excellent thermal stability

Nanotwin, renowned for its low enthalpy, is an ideal structure for improving thermal stability. Due to the difficulty of dislocation behaviors in ceramics, the effects of nanotwin on thermal stability are greatly different from nanotwinned metal materials. Herein, we reported that nanotwinned TiB0.11N1.16 ceramic coating exhibited ultra-high thermal stability, without obvious change in twin density and grain size even after annealing at 1100 degrees C for 60 min. Benefiting from the ultra-stable structures, the annealed nanotwinned coating remained super hardness of 44.5 GPa, without decrease compared to the as-deposited state, which is significantly higher than twin free TiB0.11N1.16 and other TiN-based coatings annealed under high temperature. The presence of boron segregation at grain boundaries, the network structures comprise coherent twin boundaries and incoherent twin boundaries, and the orientation constraints are responsible for the ultra-stable structure. This work provides a strategy for design of ultra-stable materials with remarkable mechanical properties under high temperature.