PVD coated tools were examined in turning at various cutting speeds, keeping all the other operating parameters constant. After thorough SEM investigations and EDX analyses of the cutting wedge at various cutting stages, an enhanced behavior as far as the first coating failure is concerned, at a cutting speed value of 200 m/min in comparison to cutting speeds of 100 and 300 m/min was observed. That was a significant indication that temperature dependent phenomena are activated, influencing the coating wear behavior.

In order to investigate the aforementioned cutting temperature dependent phenomena, coated tools were annealed at various temperatures. The annealed coated tools were tested in milling operation and the SEM investigations, the EDX analysis and the FEM simulation of the cutting edge revealed an improved coating performance in milling, in the case of the annealed specimen at 400°C.

To elucidate these results concerning the improved specimen performance, the coating material properties and more specifically the stress strain curves after various annealing temperatures were extracted by means of a developed evaluation procedure in the Laboratory for Machine Tools and Manufacturing Engineering of the Aristoteles University of Thessaloniki. The annealed coated specimen at 400°C was found to have enhanced material properties according to the determined coating constitutive law in comparison to the other annealing temperatures and the as deposited coating as well.

The fatigue and the wear behaviour of coatings on cemented carbide (HM) and high speed steel (HSS) substrates with different surface treatments are investigated experimentally in milling and in impact testing and analytically through a Finite Elements Method (FEM) simulation of the cutting and impact test process respectively. Substrate pre-treatments such as polishing, mikro-blasting, glass-blasting and coating post-treatments, as for instance mikro-finishing, edge polishing etc, are some of the investigated surface treatments.

The initiation and progress of the tool failure is depicted through Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray microspectral investigations of the used cutting edges. Furthermore the FEM simulation of the contact between the tool and the workpiece enables a quantitative description of the influence of the substrate and coating surface integrities and of the occurring mechanical stress components on the coating failure. Hereby, the coating fatigue endurance and experimentally derived technological cutting data were considered. Coating and substrate constitutive laws are also taken into account in the FEM simulations.

The obtained experimental and computational results exhibit quantitatively the influence of substrate pre-treatment as well as the coating surface post-treatment on the cutting performance.

The purpose of this study is to determine the deposition conditions to make high-purity silicon oxide films at low substrate temperatures near room temperature by inductively-coupled rf plasma-enhanced CVD. The effects of rf power and substrate position on the film composition were studied. We used a mixture of tetramethoxysilane and oxygen as a source gas. In order to obtain carbon-free silicon oxide films, the substrate temperature was kept slightly higher than the wall temperature during the deposition. The chemical compositions and bonding states of the deposited films were evaluated with Fourier transform infrared spectroscopy (FTIR).

First the rf power was varied from 50 to 300 W. FTIR analyses clearly demonstrated that the absorption bands due to OH groups were reduced markedly when the rf power increased from 50 to 300 W. At the rf power of 300 W, the absorption bands almost disappeared. The composition of the film deposited at 300 W almost corresponded with that of pure silicon oxide films prepared by thermal oxidation. In addition, a pure silicon oxide film was prepared at the substrate temperature of 50°C.

Next we investigated the effect of the substrate position on the film composition. A decrease in OH groups in the deposited films was observed with closing the distance between the center of the inductively-coupled coil and the substrate position when the substrate was located at the upstream position from the coil. The optimum substrate position was 300 mm upstream from the coil. When the distance was shorter than 300 mm, the deposition rate was very small or no film was deposited.