https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Sun, 12 Apr 2026 20:09:59 GMT 2026-04-12T20:09:59Z http://hdl.handle.net/10985/8661 Cr2C3–NiCr VPS thermal spray coatings as candidate for chromium replacement STAIA, M.H.; SUAREZ, M.; CHICOT, Didier; LESAGE, J.; IOST, Alain The present investigation has been carried out with the aim of determining the tribological behavior of a VPS chromium carbide coating both in the as-deposited and heat-treated conditions. A commercial powder of Cr2C3–25% NiCr was sprayed employing a VPS system (Medicoat AG, Switzerland) onto plain low carbon steel coupons. The samples were subsequently annealed for 2 h at 600 °C, 800 °C and 900 °C in Ar. The microstructural characterization was carried out by using SEM and XRD before and after the heat treatment of the samples. SEM observations were employed for determining the degradation mechanisms that took place during the wear tests. When the coated systems rubbed against alumina under a 5 N normal load in air, a progressive change in the mechanism, from a mixed adhesive and abrasive, to a predominant abrasive was observed, as the heat treatment temperature increased. The wear constants were found to be of the order of approximately 10− 6 mm3/N.m, which indicates a wear resistance of nearly 4 times higher in comparison with the wear results reported in the literature for similar coating systems obtained by employing HVOF deposition. However, the heat treatment carried out at 900 °C brought about only 20% increase in the sliding wear resistance of the coated system. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8661 2013-01-01T00:00:00Z STAIA, M.H. SUAREZ, M. CHICOT, Didier LESAGE, J. IOST, Alain The present investigation has been carried out with the aim of determining the tribological behavior of a VPS chromium carbide coating both in the as-deposited and heat-treated conditions. A commercial powder of Cr2C3–25% NiCr was sprayed employing a VPS system (Medicoat AG, Switzerland) onto plain low carbon steel coupons. The samples were subsequently annealed for 2 h at 600 °C, 800 °C and 900 °C in Ar. The microstructural characterization was carried out by using SEM and XRD before and after the heat treatment of the samples. SEM observations were employed for determining the degradation mechanisms that took place during the wear tests. When the coated systems rubbed against alumina under a 5 N normal load in air, a progressive change in the mechanism, from a mixed adhesive and abrasive, to a predominant abrasive was observed, as the heat treatment temperature increased. The wear constants were found to be of the order of approximately 10− 6 mm3/N.m, which indicates a wear resistance of nearly 4 times higher in comparison with the wear results reported in the literature for similar coating systems obtained by employing HVOF deposition. However, the heat treatment carried out at 900 °C brought about only 20% increase in the sliding wear resistance of the coated system. http://hdl.handle.net/10985/8559 A contact area function for Berkovich nanoindentation : Application to hardness determination of a TiHfCN thin film CHICOT, Didier; YETNA N'JOCK, M.; PUCHI-CABRERA, Eli-Saul; IOST, Alain; STAIA, M.H.; LOUIS, G.; BOUSCARRAT, G.; AUMAITRE, R. In nanoindentation, especially at very low indenter displacements, the indenter/material contact area must be defined in the best possible way in order to accurately determine the mechanical properties of the material. One of the best methodologies for the computation of the contact area has been proposed by Oliver and Pharr [W.C.Oliver, G.M.Pharr, J.Mater. Res. 7 (1992) 1564], which involves a complex phenomenological area function. Unfortunately, this formulation is only valid when the continuous stiffness measurement mode is employed. For other conditions of indentation, different contact area functions, which take into account the effective truncation length or the radius of the rounded indentertip, as well as some fitting parameters, have been proposed. However, most of these functions require a calibration procedure due to the presence of such parameters. To avoid such a calibration, in the present communication a contact area function only related to the truncation length representative of the indenter tip defect, which can be previously estimated with high resolution microscopy, has been proposed. This model allows the determination of consistent indentation data from indenter displacements of only few nanometers indepth. When this proposed contact area function is applied to the mechanical characterization of a TiHfCN film of 2.6 μm in thickness deposited onto a tool steel substrate, the direct determination of the hardness and elastic modulus of the film leads to values of 35.5±2 GPa and 490±50 GPa, respectively. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/8559 2014-01-01T00:00:00Z CHICOT, Didier YETNA N'JOCK, M. PUCHI-CABRERA, Eli-Saul IOST, Alain STAIA, M.H. LOUIS, G. BOUSCARRAT, G. AUMAITRE, R. In nanoindentation, especially at very low indenter displacements, the indenter/material contact area must be defined in the best possible way in order to accurately determine the mechanical properties of the material. One of the best methodologies for the computation of the contact area has been proposed by Oliver and Pharr [W.C.Oliver, G.M.Pharr, J.Mater. Res. 7 (1992) 1564], which involves a complex phenomenological area function. Unfortunately, this formulation is only valid when the continuous stiffness measurement mode is employed. For other conditions of indentation, different contact area functions, which take into account the effective truncation length or the radius of the rounded indentertip, as well as some fitting parameters, have been proposed. However, most of these functions require a calibration procedure due to the presence of such parameters. To avoid such a calibration, in the present communication a contact area function only related to the truncation length representative of the indenter tip defect, which can be previously estimated with high resolution microscopy, has been proposed. This model allows the determination of consistent indentation data from indenter displacements of only few nanometers indepth. When this proposed contact area function is applied to the mechanical characterization of a TiHfCN film of 2.6 μm in thickness deposited onto a tool steel substrate, the direct determination of the hardness and elastic modulus of the film leads to values of 35.5±2 GPa and 490±50 GPa, respectively. http://hdl.handle.net/10985/8560 Sliding wear of a-C:H coatings against alumina in corrosive media STAIA, M.H.; PUCHI-CABRERA, Eli-Saul; IOST, Alain; CARRASQUERO, E.; SANTANA, Y.Y.; LA BARBERA-SOSA, J.G.; CHICOT, Didier; VAN GORP, Adrien This paper reports the results obtained from the study of friction and sliding wear in two corrosive solutions of an a-C:H coating deposited on 316L stainless against an alumina ball, employed as static counter part. Calculations of the values of the von Mises stresses developed at the coating–substrate interface, as soon as the ball touches the coated sample, and how this state of stress influences the response of the coated system under the corrosion environment, are presented and discussed. The results obtained from these calculations, as well as from the experiments conducted in the present research, are compared with other experiments published in the literature, where a-C:H coatings deposited on different substrates and with different coating architectures were tested in similar corrosive media. It has been determined that in those systems, where the von Mises stress in the coating, found in the vicinity of the interface, exceeds the threshold value of approximately 370MPa, coating failure with spallation will take place, regardless of the substrate nature on which this coating has been deposited. From this analysis it has been concluded that the coating yield strength is of utmost importance in conferring the a-C:H coated system there quired stability in a corrosive solution. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8560 2013-01-01T00:00:00Z STAIA, M.H. PUCHI-CABRERA, Eli-Saul IOST, Alain CARRASQUERO, E. SANTANA, Y.Y. LA BARBERA-SOSA, J.G. CHICOT, Didier VAN GORP, Adrien This paper reports the results obtained from the study of friction and sliding wear in two corrosive solutions of an a-C:H coating deposited on 316L stainless against an alumina ball, employed as static counter part. Calculations of the values of the von Mises stresses developed at the coating–substrate interface, as soon as the ball touches the coated sample, and how this state of stress influences the response of the coated system under the corrosion environment, are presented and discussed. The results obtained from these calculations, as well as from the experiments conducted in the present research, are compared with other experiments published in the literature, where a-C:H coatings deposited on different substrates and with different coating architectures were tested in similar corrosive media. It has been determined that in those systems, where the von Mises stress in the coating, found in the vicinity of the interface, exceeds the threshold value of approximately 370MPa, coating failure with spallation will take place, regardless of the substrate nature on which this coating has been deposited. From this analysis it has been concluded that the coating yield strength is of utmost importance in conferring the a-C:H coated system there quired stability in a corrosive solution. http://hdl.handle.net/10985/9666 Fatigue behavior of a structural steel coated with a WC–10Co–4Cr/Colmonoy 88 deposit by HVOF thermal spraying LA BARBERA-SOSA, J.G.; SANTANA, Y.Y.; VILLALOBOS-GUTIERREZ, C.; CHICOT, Didier; LESAGE, J.; DECOOPMAN, Xavier; IOST, Alain; STAIA, M.H.; PUCHI-CABRERA, Eli-Saul The fatigue behavior of a SAE 4340 steel, coated with a 50% WC–10Co–4Cr/50% Colmonoy 88 deposit, by high velocity oxygen fuel (HVOF) thermal spray, has been investigated. The change in the maximum alternating stress with the number of cycles to fracture has been described by means of the relationship advanced by Stromeyer. A fractographic analysis has been carried out on some representative fracture surfaces, by means of scanning electron microscopy (SEM) techniques. The mechanical properties of the coating were characterized by means of nanoindentation tests. The results indicate that the coating is highly heterogeneous. Its deposition gives rise to a decrease in the fatigue strength of the substrate of ∼ 30%, in comparison with the uncoated substrate. The decrease in fatigue strength is due to the presence of stress concentrators at the substrate–coating interface, as well as the intrinsic characteristics of the coating. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/9666 2013-01-01T00:00:00Z LA BARBERA-SOSA, J.G. SANTANA, Y.Y. VILLALOBOS-GUTIERREZ, C. CHICOT, Didier LESAGE, J. DECOOPMAN, Xavier IOST, Alain STAIA, M.H. PUCHI-CABRERA, Eli-Saul The fatigue behavior of a SAE 4340 steel, coated with a 50% WC–10Co–4Cr/50% Colmonoy 88 deposit, by high velocity oxygen fuel (HVOF) thermal spray, has been investigated. The change in the maximum alternating stress with the number of cycles to fracture has been described by means of the relationship advanced by Stromeyer. A fractographic analysis has been carried out on some representative fracture surfaces, by means of scanning electron microscopy (SEM) techniques. The mechanical properties of the coating were characterized by means of nanoindentation tests. The results indicate that the coating is highly heterogeneous. Its deposition gives rise to a decrease in the fatigue strength of the substrate of ∼ 30%, in comparison with the uncoated substrate. The decrease in fatigue strength is due to the presence of stress concentrators at the substrate–coating interface, as well as the intrinsic characteristics of the coating. http://hdl.handle.net/10985/9658 A description of the composite elastic modulus of multilayer coated systems PUCHI-CABRERA, Eli-Saul; STAIA, M.H.; IOST, Alain The evaluation of the elastic response of coated systems under indentation loading represents a crucial issue, which determines the behavior of such systems under tribological applications. Although a number of models have been proposed in the literature for the description of the change in the composite modulus with indentation depth, as well as for the determination of the elastic modulus of monolayer coatings, only few works address the analysis of multilayer coatings. The present work proposes a general methodology, which allows the modification and extension of the models employed in the analysis of monolayer coatings, for the study of the elastic response of multilayer coatings. For this purpose, a number of models have been examined, including those proposed by Gao et al., Menčík et al., Perriot and Barthel, Antunes et al., Korsunsky and Constantinescu, Doerner and Nix, Bec et al. and Bull. The foundation of the advanced formalism is the physically-based concept proposed by Iost et al. for the computation of the volume fraction of each layer in the coating and therefore, of its contribution to the global elastic response under indentation. The modified models are further employed in the analysis of a coated system composed of a 2024-T6 aluminum alloy substrate coated with a multilayer coating of DLC/CrC/CNiPCr/NiP of approximately 54 μm in thickness, as well as, a set of experimental data reported by Bull for a bilayer coated system. It has been shown that the different models analyzed are able to provide a satisfactory description of the experimental data, although the quality of the fit depends on the number of material parameters involved in each model. The mean square error of the fit is employed for conducting a comparison between the models. Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/9658 2015-01-01T00:00:00Z PUCHI-CABRERA, Eli-Saul STAIA, M.H. IOST, Alain The evaluation of the elastic response of coated systems under indentation loading represents a crucial issue, which determines the behavior of such systems under tribological applications. Although a number of models have been proposed in the literature for the description of the change in the composite modulus with indentation depth, as well as for the determination of the elastic modulus of monolayer coatings, only few works address the analysis of multilayer coatings. The present work proposes a general methodology, which allows the modification and extension of the models employed in the analysis of monolayer coatings, for the study of the elastic response of multilayer coatings. For this purpose, a number of models have been examined, including those proposed by Gao et al., Menčík et al., Perriot and Barthel, Antunes et al., Korsunsky and Constantinescu, Doerner and Nix, Bec et al. and Bull. The foundation of the advanced formalism is the physically-based concept proposed by Iost et al. for the computation of the volume fraction of each layer in the coating and therefore, of its contribution to the global elastic response under indentation. The modified models are further employed in the analysis of a coated system composed of a 2024-T6 aluminum alloy substrate coated with a multilayer coating of DLC/CrC/CNiPCr/NiP of approximately 54 μm in thickness, as well as, a set of experimental data reported by Bull for a bilayer coated system. It has been shown that the different models analyzed are able to provide a satisfactory description of the experimental data, although the quality of the fit depends on the number of material parameters involved in each model. The mean square error of the fit is employed for conducting a comparison between the models. http://hdl.handle.net/10985/9673 Effect of O2 increase on properties of vanadium oxide coatings ZAIRI, Amel; BEN CHEIKH LARBI, A.; IOST, Alain; STAIA, M.H. The present research was carried out with the aim of studying the influence of oxygen concentration during processing on the properties of the VOx coatings deposited by cathodic magnetron sputtering on a stainless steel AISI 316L substrate. Mechanical and tribological properties were measured by nanoindentation and sliding wear tests respectively. Adhesion was evaluated by means of the scratch test. In order to determine the texture of the coatings, complementary characterization methods including X-ray diffraction in grazing incidence and Bragg Brentano configurations, as well as V scans, were performed. It was found that the texture of the crystalline coatings is strongly influenced by the amount of partial pressure of oxygen in the reactor atmosphere. The V2O5 phase, with an orthorhombic symmetry, was produced in the coating, which had a pronounced texturing for the (001) plane, exhibiting the best values of hardness and Young modulus. It was shown that, as the oxygen concentration drops to ,1 sccm, the mechanical and tribological characteristics, as well as the coating adhesion, tend to decrease considerably. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/9673 2014-01-01T00:00:00Z ZAIRI, Amel BEN CHEIKH LARBI, A. IOST, Alain STAIA, M.H. The present research was carried out with the aim of studying the influence of oxygen concentration during processing on the properties of the VOx coatings deposited by cathodic magnetron sputtering on a stainless steel AISI 316L substrate. Mechanical and tribological properties were measured by nanoindentation and sliding wear tests respectively. Adhesion was evaluated by means of the scratch test. In order to determine the texture of the coatings, complementary characterization methods including X-ray diffraction in grazing incidence and Bragg Brentano configurations, as well as V scans, were performed. It was found that the texture of the crystalline coatings is strongly influenced by the amount of partial pressure of oxygen in the reactor atmosphere. The V2O5 phase, with an orthorhombic symmetry, was produced in the coating, which had a pronounced texturing for the (001) plane, exhibiting the best values of hardness and Young modulus. It was shown that, as the oxygen concentration drops to ,1 sccm, the mechanical and tribological characteristics, as well as the coating adhesion, tend to decrease considerably.