Morphology, mechanical properties, and oxidation behavior of reactively sputtered Cr–N films

Cr–N films with various compositions and structures are deposited by reactive sputtering on A2 tool steel. Phase identification indicates that films with lower nitrogen contents exhibit Cr and Cr2N phases, while the CrN phase is observed in films with nitrogen contents higher than 58 at.%. The microhardness of the deposited film ranges from 1500 to 1800 HK at a load of 3 gf with a Knoop indenter. During the oxidation test, Cr2O3 are formed on top of films. The phase analysis of the oxidized samples indicates that the pre-existed Cr and Cr2N phases in the deposited films are transformed to CrN due to the incorporation of nitrogen released by the oxidation layers. It is observed that the oxidation resistance of films with CrN phase is better than that with Cr or Cr2N phases.