Microstructure evolution and nanohardness of nanostructured TiAlN coating under N+ ion irradiation

The present study deals with nanostructured TiAlN coating materials irradiated by 1.4 MeV N+ ions with different fluences and temperatures. The TiAlN coatings were synthesized by cathodic arc ion plating with average grain size of 10.5 nm. The microstructure evolution and nanohardness of coatings were investigated before and after irradiation by using TEM, GIXRD and nanoindentation. Our findings showed that there are no phase segregation and amorphization observed in all irradiated samples, indicating a good irradiation resistance of nano-structured TiAlN coating. Meanwhile, a great number of N bubbles have been observed located within grains and along the grain boundaries when the fluence exceeds 2.0 × 1016 ion/cm2 at room temperature irradiation. The nanoindentation results showed an obvious radiation-induced softening (RIS) effect in TiAlN coatings which is susceptible to the irradiation fluence and the irradiation temperature. It is found that the formation and the evolution of N bubbles located along the grain boundaries may dominate the RIS effect.