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The determination of the temperature dependent interface fatigue strength of Nano-Crystalline Diamond (NCD) coatings facilitates a thorough understanding of the NCD coated cutting tools wear mechanisms. In the present paper, the fatigue strength of the interface region between a NCD film and its hardmetal substrate was investigated by inclined impact tests at various temperatures. Depending upon the impact load and the applied temperature, after a certain number of impacts, damages in the film-substrate interface develop, resulting in coating detachment and lifting. These effects were attributed among others to the release of highly compressive residual stresses in the NCD coating structure. The attained inclined impact test's results contributed to the explanation of the wear-evolution of NCD-coated tools with diverse film-substrate adhesion qualities. The related milling experiments using as work material AA 7075 T6 verified the dominant effect of the film adhesion on the NCD coated tool life. [ABSTRACT FROM AUTHOR]

If the film of a coated part deforms plastically due to operational loads, residual stresses (RS) develop in the coating after the load removal. In this way, the film mechanical properties change induced by endogenous reasons, i.e. by the coating crystalline structure plastic deformation. Moreover, if only the substrate deforms plastically, the coating remains elastically deformed during the relaxation, due to the substrate RS. In this case, the film residual RS-changes are caused by exogenous parameters, i.e by the permanent substrate deformation. In the paper, novel experimental-analytical methods, based on nanoindentation and FEM calculations are introduced to determine film RS-changes, when the coating is deformed plastically as for example after micro-blasting, or elastically due to substrate plastic deformation as for instance after the ball penetration into the coated specimen during the impact test. [ABSTRACT FROM AUTHOR]