Ta-Si-N coatings were prepared using reactive direct current magnetron co-sputtering on silicon substrates. When the sputtering powers and N-2 flow ratio were varied, Ta-Si-N coatings exhibited various chemical compositions and crystalline characteristics. The high-Si-content Ta-Si-N coatings exhibited an amorphous phase in the as-deposited states, whereas the low-Si-content coatings exhibited a facecentered cubic phase or an amorphous phase depending on the N content. This study evaluated the application of amorphous Ta-Si-N coatings, such as the protective coatings on glass molding dies, in high-temperature and oxygen-containing atmospheres for longed operation durations. To explore the oxidation resistance and mechanical properties of the Ta-Si-N coatings, annealing treatments were conducted in a 1%02-99%Ar atmosphere at 600 C for 4-100 h. The material characteristics and oxidation behavior of the annealed Ta-Si-N coatings were examined using atomic force microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and a nanoindentation tester. The Si oxidized preferentially in the Ta-Si-N coatings. The in-diffusion of oxygen during 600 C annealing was restricted by the formation of an amorphous oxide scale consisting of Si and O. (C) 2014 Elsevier B.V. All rights reserved.