Interface defects and stress relief of super hard Ti+C/a-CNx gradient multilayer films

Ti + C/a-CNx gradient multilayer film (GMF) are prepared using ion-beam assisted magnetron sputtering. The hardness of as-deposited Ti + C/a-CNx-GMF reach 29 GPa, which is obviously higher that of pure CNx film. Transmission electron microscopy (TEM) and optical microscope (OM) were used to examine the structure and morphologies of Ti + C/a-CNx-GMF films. Investigation results indicated that there was a Ti + C gradient layer zone with gradual Ti lattice parameter existed in this super hard Ti + C/a-CNx-GMF, and interface zones are mainly composed of nanocrystallie TiC and Ti grains and amorphous matrix, the growth of interlayer depends on compressive stress. As deposited GMFs voluntarily buckling and peeling along the interfacial defect zone (Ti-Si-O), due to the existence of high internal stress in films, lead to adhesion failure. After undergoing thermal treatment, Ti + C gradient multilayer (GM) zone present a semi-coherent type with some misfit, which could relax the internal stress of GMFs. (C) 2017 Elsevier Ltd. All rights reserved.