WN and W-C (14.8 at.%)-N coatings were prepared by reactive magnetron sputtering to investigate the oxidation behavior during heat treatment. The results show that the deposited WN and WCN coatings are compact and grow with a columnar structure. The incorporation of carbon does not affect the columnar structure and some amorphous phases formed among the columnar grain boundaries. The addition of carbon to columnar WN coating could improve the oxidation resistance by increasing the bonding energy, decreasing the pores among the columnar grain boundaries, squeezing the amorphous phase to withstand the expansion of oxidation and consuming some oxygen by oxidizing amorphous phase. (C) 2017 Elsevier B.V. All rights reserved.