Browsing by Author "Benlatreche, Y."

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Applications of CrAlN ternary system in wood machining of medium density fibreboard (MDF)
(2009) Benlatreche, Y.; Nouveau, C.; Marchal, R.; Martins, J-P. F.; Aknouche, Hamid
Nowadays, medium density fibreboard (MDF) composite wood is more and more used in the furniture industry to replace bulk wood such as oak, beech, etc. Indeed, this material presents good mechanical properties, is easy to machine, homogeneous, exists in different dimensions (thickness, etc.), is cheaper than bulk wood and finally can be covered by an adhesive decorative coat. Nevertheless, even if this material is homogeneous, it is abrasive enough to tend to the breakdown of the conventional carbide tools employed during its routing process. That is why it is necessary to improve the wear resistance of these tools. One solution is to protect them with a hard coating. The present study deals with the development of ternary CrAlN hard layers obtained by PVD method on carbide tools employed in second transformation of wood. CrAlN coatings have been optimized and then applied on carbide tools in routing of three types of MDF: standard, waterproof and fireproof. The aim of these wood machining tests was first to define the ability to be machined of the three kinds of MDF and second to compare the effectiveness of CrAlN coatings during the routing tests of these materials
Comparison of CrAlN layers obtained with one (CrAl)or two targets (Cr and Al) by magnetron sputtering
(2012) Nouveau, C.; Tlili, B.; Aknouche, Hamid; Benlatreche, Y.; Patel, B.
The aim of this study is to compare the properties of CrAlN coatings obtained by magnetron sputtering with one (CrAl) or two targets (Cr and Al). The influence of parameters such as the target bias voltage, the working pressure, the deposition time and the bias voltage applied on the Cr or Al targets on the properties of the layers was studied. We characterized the films by X-ray Diffraction, Scanning Electron Microscopy, coupled with Energy Dispersive Spectroscopy, nanoindentation and their residual stresses were also determined. The optimal films obtained with both methods are well crystallized, well-adherent to the substrate, and contained similar amounts of Al (20–30 at.%). The optimal coatings synthesized with one target presented properties not as good as those realized with two targets. Nevertheless, films made with one target showed a lower frictional coefficient probably due to composition control. The lack of compositional control with the use of one target limits the optimization process. With two targets, we have greater control over the film composition. This leads to higher hardness, lower stresses, and improved Young's modulus over films produced with a single CrAl target. Additionally, the morphologies are different (columnar with CrAl and dense with Cr and Al). To conclude, it seems more justified to work if possible with two independent targets
Physical and mechanical properties of CrAlN and CrSiN ternary systems for wood machining applications
(2009) Benlatreche, Y.; Nouveau, C.; Aknouche, Hamid; Imhoff, L.; Martin, N.; Gavoille, J.; Rousselot, C.; Yves Rauch, J.; Pilloud, D.
Nowadays, almost all the cutting tools in metal machining are protected with a surface treatment. Nevertheless, this is not the case in woodmachining where no tools are protected, except by thermal treatments, and so they present a previous wear because of the use of steel or carbide materials in milling, sawing, routing, etc. During these processes, the tools are particularly exposed to abrasive and shock wear. To enhance their wear resistance, one solution is to protect them with hard coatings. The present study deals with the development of ternary systems (CrAlN and CrSiN) obtained by two PVD different magnetron sputtering systems [‘A’ (laboratory where CrAlN layers have been obtained) and ‘B’ (laboratory where CrSiN layers have been obtained) in the following text] on carbide WC–Co tools used in second transformation of wood to be compared to the binary CrN one. CrAlN and CrSiN films were deposited with different Al and Si contents, respectively, in order to check the effect of the additive element (Al or Si) on the different properties of the Cr–N system. The different coatings were characterized by SEM and EDS for thickness measurements, morphology and composition analyses, respectively, by nanoindentation for hardness and Young’s modulus measurements and by pin-on-disc to determine their friction coefficient. Routing of medium density fibreboard (MDF) was realized employing untreated or modified carbide WC–Co tools in order to compare their wear resistance. We observed that the Al and the Si addition improved the hardness and the Young’s modulus of the Cr–N system (‘A’: 29 and 410 GPa, respectively, ‘B’: 18 and 280 GPa, respectively). Indeed, the hardness values are 15–36GPa for CrAlN and 15–24 GPa for CrSiN coatings. Besides, the Young’s modulus values are 331–520GPa for CrAlN and 260–320 GPa for CrSiN coatings. The friction coefficient of the CrAlN layers varied between 0.6 and 0.7 and it increased slightly with the Al content. For the CrSiN coatings, the friction coefficient was lower and about 0.4. In both cases, the CrN layers ‘A’ and ‘B’ presented similar friction coefficient than CrAlN and CrSiN, respectively. During the routing of MDF, the CrN ‘A’ coating has a similar wear behaviour than the optimized CrAlN one (5 at.% of Al) while the optimized CrSiN coating (1.2 at.% of Si) showed a better behaviour against wear than the CrN ‘B’ one. The wear resistance of CrAlN- and CrSiN-coated carbide tools decreased when the Al and Si contents increased