This work aims to show the characterisation of Cr-V-N coatings, with the varied amounts of Cr and V. CrN, VN and Cr-V-N coatings were deposited onto silicon and XC100 steel substrates by reactive radio frequency magnetron sputtering and characterised with X-ray diffraction, X-ray photoelectron spectroscopies, energy dispersive X-ray spectroscopy, scanning electron microscopy, nanoindentation, pin on disc tribological tests and scratch tests. The residual stress was calculated using the Stoney formula. Compared to the CrN system, the Cr-V-N films presented a rough surface based on pyramidal morphology. A hardness of 19?53 GPa and a friction coefficient of 0?55 were obtained for CrN; in contrast, Cr-V-N coatings presented a weak hardness of 6?23 GPa. In the case of wear against a 100Cr6 ball, the Cr-V-N films were completely removed from the substrate, even though the Cr-V-N coating presented a low friction coefficient (0?39). However, the VN film showed good tribological performance.

We investigated the effect of film thickness on the structure and properties of VeN coatings deposited by magnetron sputtering in an argon and nitrogen atmosphere. The nitrogen percentage was changed between 10 and 20%. Firstly, structural and morphological properties of VeN films were observed, analyzed and subsequently followed by a detailed investigation on the mechanical and tribological properties of these coatings. It has been shown that film structure, hardness and wear resistance significantly changed with varying the film thickness and the nitrogen percentage. In the case of films deposited under 10%N 2 , the presence of V 2 N phase was evident. With increasing nitrogen ratio in the deposition chamber from 10 to 20%, the structure was changed from (hc)V 2 N to multi phases of V 2 N and (fcc) VN (formation of different vanadium nitrides). The thick films containing more nitrogen were slightly dense compared to the thinner ones presenting rough surface and columnar morphology. Nanoindentation measurements showed that film mechanical behavior depends on its thickness, nitrogen percentage and microstructural features. The film hardness first increased with its thickness and then decreased. The highest hardness of 26.2 GPa was obtained for the film deposited under 20%N 2 , which is correlated with its dense structure and film stoichiometry. The film thickness has a significant effect on the tribological properties of VeN films. The minimum friction coefficient of 0.4 was found for the thickest film of 2500 nm. The wear rate gradually decreased with increasing the film thickness, due to the high hardness, presence of VN phase and the strong adhesion between film and substrate.

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. a b s t r a c tCrN/CrAlN and Cr/CrN/CrAlN multilayers were grown with dual RF magnetron sputtering. The application of these multilayers will be wood machining of green wood. That is why ball-on-disc and electrochemical tests in NaCl aqueous solution were realized to elucidate the tribological and corrosion behavior of these coatings as they will be exposed to wear and corrosion during wood machining process. The samples/alumina and samples/WC coupling showed different wear mechanisms. The 300 nm thick Cr/CrN/CrAlN multilayer demonstrated the best tribological behavior and corrosion resistance. The influence of growth defects on corrosion resistance has been shown. .

is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. The aim of the study is to apply a plasma nitriding process to the 90CrMoV8 steel commonly employed in wood machining, and to determine its efficiency to improve both mechanical and electrochemical properties of the surface. Treatments were performed at a constant N 2 :H 2 gas mixture and by varying the temperature and process duration. The structural and morphological properties of nitrided layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with EDS microanalyses. Surface hardening and hardness profiles were evaluated by micro hardness measurements. To simulate the wood machining conditions, electrochemical tests were carried out with an oak wood electrolyte with the purpose of understanding the effects of the nitriding treatment on the corrosion resistance of the tool in operation. X-ray diffraction analyses revealed the presence of both γ′ (Fe 4 N) and ε (Fe 2-3 N) nitrides with a predominance of the ε phase. Moreover, α-Fe (110), γ′ and ε diffraction peaks were shifted to lower angles suggesting the development of compressive stresses in the post nitrided steel. As a result, it was shown that nitriding allowed a significant hardening of steel with hardness values higher than 1200 HV. The diffusion layers were always composed of an outer compound layer and a hardened bulk layer which thickness was half of the total diffusion layer one. No white layer was observed. Similarly, no traces of chromium nitrides were detected. The temperature seemed to be a parameter more influent than the process duration on the morphological properties of the nitrided layer, while it had no real influence on their crystallinity. Finally, the optimal nitriding conditions to obtain a thick and hard diffusion layer are 500°C for 10 h. On the other hand, to verify the effect of these parameters on the corrosion resistance, potentiodynamic polarization tests were carried out in an original "wood juice" electrolyte. After corrosion, surface was then observed at the SEM scale. Electrochemical study indicated that the untreated steel behaved as a passive material. Although the very noble character of steel was somewhat mitigated and the corrosion propensity increased for nitrided steels, the passive-like nature of the modified surface was preserved. For the same optimized parameters as those deduced from the mechanical characterization (500°C, 10 h), surface presented, in addition to a huge surface hardening, a high corrosion resistance.

a b s t r a c tThe objective of this study is to examine the sudden drop in properties of aluminum, titanium and chromium thin films prepared by the glancing angle deposition method. The thin films were deposited by DC magnetron sputtering under identical deposition conditions. A substrate-holder with seven different orientations with respect to the target normal was used. The thickness and the column tilt angles (b) of the thin films were determined by scanning electron microscopy. The residual stress of the thin films was evaluated using the wafer curvature technique and calculated by the Stoney's formula. The thickness variation and column tilt angle versus the orientation of the substrate indicated that the critical point is around 60 for all metallic materials and a critical angle of 60 is also found for the residual stress. Simulations of the particles transport are compared to the experimental data and moderate the critical angles analyses.

Chromium nitrides were deposited by RF reactive magnetron sputtering from a Cr target on high carbon steel substrates XC100 (1.17 wt% carbon) in a N 2 and Ar gas mixture. In order to investigate the formation of chromium nitrides, carbide and carbonitride compounds were subjected to vacuum annealing treatment for 1 h at various temperatures ranging from 700 to 1000°C. The samples were characterized by EDS, XPS, XRD, SEM, nanoindentation and tribometry. The results showed the emergence of Cr 2 N and CrN during the early stages of annealing and the appearance of chromium carbonitride phases only at 900°C. The (111) preferred orientation of the fcc CrN phase was changed to (002) at 900°C in parallel with the appearance of chromium carbides. Nanoindentation tests revealed a gradual increase of the Young's modulus from 198 to 264 GPa when increasing the annealing temperature, while the hardness showed a maximum value (H = 22.4 GPa) at 900°C. The low friction coefficient of the CreCeN coating against a 100Cr6 ball was approximately 0.42 at 900°C. The enhancement of mechanical and tribological properties was attributed to the stronger bonding CreC at the CrN/ XC100 interfaces as confirmed by XPS results.

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