Amorphous carbon nitride (CNx) coatings are now being developed for a range of applications, e.g. as a protective top layer for hard disks or as a coating to reduce the friction between synthetic joints in the human body. The purpose of this work is to assess the mechanical properties of the latest generation of fullerene-like CNx deposited on different substrates in order to expand the number of potential applications. Samples of CNx on four different substrates have been studied using quasistatic nanoindentation with a wide range of peak loads, from 500 mu N to 500 mN and dynamic nanoindentation for peak loads from 100 mu N to up to 10 mN. Improved deposition techniques generate samples with extremely high values of hardness/Young's modulus; in some cases greater than 0.4 which is not achieved by any other hard material. Adhesion and fracture resistance are comparable to or better than that of traditional high hardness coatings, such as SiC and TiN, on similar substrates. The sample of CNx on titanium showed differences in hardness and Young's modulus at low loads, where the influence of the substrate is negligible, compared to coatings deposited on other substrates. This arises due to the fact that Ti from the substrate may have diffused into the coating in the deposition process creating a sort of C-N-Ti high hardness layer which would have some advantages of both the fullerene-like and traditional hard coating systems. (c) 2005 Elsevier B.V. All rights reserved.