Properties and characterization of multilayers of carbides and diamond-like carbon

Metal containing diamond-like carbon (Me-DLC) coatings are widely applied in industrial applications. Normally, the coatings are produced with small inclusions of carbide forming elements like the 3d, 4d or 5d metals, or Si or B. The small carbide islands have sizes of approximately 2-20 nm. The effect of the nano inclusions is a reduction of internal compressive stress, a lowering of Young’s modulus, a lower hardness, and a higher coefficient of friction as compared to pure diamond-like carbon (DLC). The contents of metallic elements are typically between 10 and 20 at.%; for B containing diamond-like carbon a higher percentage is observed (up to 50% B). In this work the effect of replacing the nano inclusions by a stack of extremely thin carbide layers, separated by carbon layers, is tested. Properties like adhesion, hardness, E-modulus, fatigue resistance, coefficient of friction and wear resistance were studied. Furthermore, detailed high resolution TEM was performed to observe the effects of layer integrity. The results show a clear difference in wear and fatigue behavior when the multilayer structure was altered. Short periods within the multilayer structure of W-C:H promotes the wear resistance, while long periods promote the fatigue resistance.