A comparative study of microstructure and mechanical properties for CrNx films with various deposition rates by magnetron sputtering

This paper investigated the effect of the film deposition rate for CrNx films on microstructure and mechanical properties. For these purposes, pure Cr and nearly stoichiometric CrN films were deposited with various target power densities on Si wafer and hardened M2 tool steel. The variation of nitrogen concentration in CrNx films was analyzed by AES and the deposition rate was calculated by measuring film thickness using an a-step profilometer. The microstructure was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and mechanical properties were evaluated by residual stress, microhardness and adhesion tests. Deposition rate of Cr and CrN films was increased as an almost linear function of target power density from 0.25 to 0.6 μm/min and 0.15 to 0.43 μm/min. Residual stresses of Cr and CrN films were changed from tensile to compressive stress with an increase of deposition rate and residual compressive stresses were increased as more augmentation of deposition rate. The maximum hardness value of 2300 kg/mm2 and the best adhesion strength corresponding to HF 1 were obtained for CrN film synthesized at the highest target power density (13.2 W/cm2) owing to high residual compressive stress and increasing adatom mobility.