Chromium nitride (CrN) coating has been identified as one of the promising protective coatings for molding applications.Critical features of CrN include wear resistance,corrosion resistance,oxidation resistance,and most importantly,ease of mold release.CrN will form a dense and stable Cr2O3 thin film as a protective surface scale at the elevated temperature.Previous study reveals that chromium oxynitride (Cr(N,O)) films exhibits higher hardness than CrN.It is presumed that Cr(N,O) films with a low nitrogen content can be based on the Cr2O3 structure which has been used for the protective coating of mechanical components.In this study,the CrN coating was first deposited on tool steels by cathodic arc evaporation technique and then this coating was subjected to oxygen glow discharge to activate the oxidation of CrN coating in order to form oxide layer on the surface.In the analysis process,we investigate the various properties of CrN coatings in terms of hardness,adhesion,microstructure and surface morphology by using Micro Hardness tester,Rockwell indentation,X-ray diffractometer (XRD),Field Emission Scanning Electron Microscopy (FESEM).The effect of the oxygen plasma on the CrN coating is investigated.The results of this study are turned out that hardness of CrN coating was improved due to the oxide layer on the surface of CrN.It is therefore expected to facilitate the performance of CrN coatings for industrial applications.