TiAlSiN nanocomposite and TiN coatings were synthesized by multi-plasma immersion ion implantation and deposition. The structure, hardness and tribological properties of both coatings oxidized at 800°C were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, nano-indentation and ball-on-disk tests. The results show that the TiN coating was oxidized almost completely after air exposure at 800°C. Except for a thin oxidized layer formed on the top surface containing TiO 2 , Al 2 O 3 and SiO 2 , the cross section of the TiAlSiN coating remained in its original configuration after oxidation. Analysis revealed that the oxidized layer remained in a similar structure as before oxidation, which is TiO 2 nanocrystals embedded in an amorphous SiO 2 matrix. The hardness results show that the TiAlSiN coating after oxidation maintained a similar hardness as the un-oxidized coating. In addition, the TiAlSiN coating also showed a high wear resistance at 800°C.