https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Fri, 05 Jun 2026 23:29:37 GMT 2026-06-05T23:29:37Z http://hdl.handle.net/10985/8662 Analysis of indentation size effect in copper and its alloys CHICOT, Didier; PUCHI-CABRERA, Eli-Saul; IOST, Alain; STAIA, M.H; DECOOPMAN, Xavier; ROUDET, F.; LOUIS, G. For describing the indentation size effect (ISE), numerous models, which relate the load or hardness to the indent dimensions, have been proposed. Unfortunately, it is still difficult to associate the different parameters involved in such relationships with physical or mechanical properties of the material. This is an unsolved problem since the ISE can be associated with various causes such as workhardening, roughness, piling-up, sinking-in, indenter tip geometry, surface energy, varying composition and crystal anisotropy. For interpreting the change in hardness with indent size, an original approach is proposed on the basis of composite hardness modelling together with the use of a simple model, which allows the determination of the hardness–depth profile. Applied to copper and copper alloys, it is shown that it is possible to determine the maximum hardness value reached at the outer surface of the material and the distance over which both the ISE and the workhardening take place. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8662 2013-01-01T00:00:00Z CHICOT, Didier PUCHI-CABRERA, Eli-Saul IOST, Alain STAIA, M.H DECOOPMAN, Xavier ROUDET, F. LOUIS, G. For describing the indentation size effect (ISE), numerous models, which relate the load or hardness to the indent dimensions, have been proposed. Unfortunately, it is still difficult to associate the different parameters involved in such relationships with physical or mechanical properties of the material. This is an unsolved problem since the ISE can be associated with various causes such as workhardening, roughness, piling-up, sinking-in, indenter tip geometry, surface energy, varying composition and crystal anisotropy. For interpreting the change in hardness with indent size, an original approach is proposed on the basis of composite hardness modelling together with the use of a simple model, which allows the determination of the hardness–depth profile. Applied to copper and copper alloys, it is shown that it is possible to determine the maximum hardness value reached at the outer surface of the material and the distance over which both the ISE and the workhardening take place. 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/10985/8554 An analysis of the elastic properties of a porous aluminium oxide film by means of indentation techniques HEMMOUCHE, L.; CHICOT, Didier; AMROUCHE, A.; IOST, Alain; BELOUCHRANI, M.A.; DECOOPMAN, Xavier; LOUIS, G.; PUCHI-CABRERA, Eli-Saul The elastic modulus of thin films can be directly determined by instrumented indentation when the indenter penetration does not exceed a fraction of the film thickness, depending on the mechanical properties of both film and substrate. When it is not possible, application of models for separating the contribution of the substrate is necessary. In this work, the robustness of several models is analyzed in the case of the elastic modulus determination of a porous aluminium oxide film produced by anodization of an aluminium alloy. Instrumented indentation tests employing a Berkovich indenter were performe data nanometric scale, which allowed a direct determination of the film elastic modulus, whose value was found to be approximately 11 GPa. However, at a micrometric scale the elastic modulus tends toward the value corresponding to the substrate, of approximately 73 GPa. The objective of the present work is to apply different models for testing their consistency over the complete set of indentation data obtained from both classical tests in microindentation and the continuous stiffness measurement mode in nanoindentation. This approach shows the continuity between the two scales of measurement thus allowing a better representation of the elastic modulus variation between two limits corresponding to the substrate and film elastic moduli. Gao's function proved to be the best to represen the elastic modulus variation. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8554 2013-01-01T00:00:00Z HEMMOUCHE, L. CHICOT, Didier AMROUCHE, A. IOST, Alain BELOUCHRANI, M.A. DECOOPMAN, Xavier LOUIS, G. PUCHI-CABRERA, Eli-Saul The elastic modulus of thin films can be directly determined by instrumented indentation when the indenter penetration does not exceed a fraction of the film thickness, depending on the mechanical properties of both film and substrate. When it is not possible, application of models for separating the contribution of the substrate is necessary. In this work, the robustness of several models is analyzed in the case of the elastic modulus determination of a porous aluminium oxide film produced by anodization of an aluminium alloy. Instrumented indentation tests employing a Berkovich indenter were performe data nanometric scale, which allowed a direct determination of the film elastic modulus, whose value was found to be approximately 11 GPa. However, at a micrometric scale the elastic modulus tends toward the value corresponding to the substrate, of approximately 73 GPa. The objective of the present work is to apply different models for testing their consistency over the complete set of indentation data obtained from both classical tests in microindentation and the continuous stiffness measurement mode in nanoindentation. This approach shows the continuity between the two scales of measurement thus allowing a better representation of the elastic modulus variation between two limits corresponding to the substrate and film elastic moduli. Gao's function proved to be the best to represen the elastic modulus variation. http://hdl.handle.net/10985/9674 Sliding Wear Response of Nanostructured YSZ Suspension Plasma-Sprayed Coating KOSSMAN, Stephania; CHICOT, Didier; DECOOPMAN, Xavier; IOST, Alain; VAN GORP, Adrien; MEILLOT, E.; PUCHI-CABRERA, Eli-Saul; SANTANA, Y.Y.; STAIA, Mariana Nanostructured yttria-stabilized zirconia coatings for applications in high-temperature environments can be deposited by suspension plasma spraying (SPS) techniques. The present research has been conducted in order to study the sliding wear response of a SPS ZrO2–8% mol. Y2O3 coating (75 lm in thickness) deposited onto a Haynes 230 substrate, using pin-on-disc tests. Some of the coated samples were subsequently heat-treated for 1 h at 300 and 600 !C. Samples characterization prior and after the wear tests was carried out by SEM, EDS, XRD and optical profilometry techniques. Instrumented indentation was employed to determine elastic modulus and hardness. The results have shown that the as-sprayed and heat-treated samples experienced severe wear (10213 m3/Nm) and the worst wear performance corresponded to the sample heat treated at 600 !C. Such a behavior could be related to both the structural changes that took place during heat treatment and the nature and level of the residual stresses in the coatings. In general, the morphologies of the wear tracks observed by SEM have shown a smoothing of the surface, brittle fracture, smearing and grain pull-out. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/9674 2014-01-01T00:00:00Z KOSSMAN, Stephania CHICOT, Didier DECOOPMAN, Xavier IOST, Alain VAN GORP, Adrien MEILLOT, E. PUCHI-CABRERA, Eli-Saul SANTANA, Y.Y. STAIA, Mariana Nanostructured yttria-stabilized zirconia coatings for applications in high-temperature environments can be deposited by suspension plasma spraying (SPS) techniques. The present research has been conducted in order to study the sliding wear response of a SPS ZrO2–8% mol. Y2O3 coating (75 lm in thickness) deposited onto a Haynes 230 substrate, using pin-on-disc tests. Some of the coated samples were subsequently heat-treated for 1 h at 300 and 600 !C. Samples characterization prior and after the wear tests was carried out by SEM, EDS, XRD and optical profilometry techniques. Instrumented indentation was employed to determine elastic modulus and hardness. The results have shown that the as-sprayed and heat-treated samples experienced severe wear (10213 m3/Nm) and the worst wear performance corresponded to the sample heat treated at 600 !C. Such a behavior could be related to both the structural changes that took place during heat treatment and the nature and level of the residual stresses in the coatings. In general, the morphologies of the wear tracks observed by SEM have shown a smoothing of the surface, brittle fracture, smearing and grain pull-out. http://hdl.handle.net/10985/10875 Multi-scale approach of the instrumented indentation technique on the fracture toughness estimation MEJIAS, A; CHICOT, Didier; DECOOPMAN, Xavier; ROUDET, Francine; IOST, Alain; MONTAGNE, Alex Instrumented Indentation Technique (IIT) is widely used to determine the mechanical properties of materials. The elastic modulus is usually determined by applying the methodology proposed by Oliver and Pharr [1] who supposed that its value is independent of the indentation depth. However, some authors [2, 3] have observed a decrease of the elastic modulus when the indenter displacement increases which allowed them to introduce a continuous damage theory used afterwards to estimate the fracture toughness of ductile materials. The assumption made by the authors is that a damage in the region very close to the bottom of the indent results in the formation of microvoids which leads to the variation of the elastic modulus as a function of the indenter displacement. Starting from this observation, Lee et al. [2] proposed an energy model based on the Griffith’s theory and the continuous damage mechanics (CDM) which states that the elastic modulus variation is related to the fraction void volume through a variable damage, introduced by Kachanov [4], related to the surface density of the microdefects. On the other hand, the works carried out over ductile materials by Li et al. [3] have been performed only with nanoindentation data preventing a discussion on the scale-­‐effect. (...) Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/10875 2015-01-01T00:00:00Z MEJIAS, A CHICOT, Didier DECOOPMAN, Xavier ROUDET, Francine IOST, Alain MONTAGNE, Alex Instrumented Indentation Technique (IIT) is widely used to determine the mechanical properties of materials. The elastic modulus is usually determined by applying the methodology proposed by Oliver and Pharr [1] who supposed that its value is independent of the indentation depth. However, some authors [2, 3] have observed a decrease of the elastic modulus when the indenter displacement increases which allowed them to introduce a continuous damage theory used afterwards to estimate the fracture toughness of ductile materials. The assumption made by the authors is that a damage in the region very close to the bottom of the indent results in the formation of microvoids which leads to the variation of the elastic modulus as a function of the indenter displacement. Starting from this observation, Lee et al. [2] proposed an energy model based on the Griffith’s theory and the continuous damage mechanics (CDM) which states that the elastic modulus variation is related to the fraction void volume through a variable damage, introduced by Kachanov [4], related to the surface density of the microdefects. On the other hand, the works carried out over ductile materials by Li et al. [3] have been performed only with nanoindentation data preventing a discussion on the scale-­‐effect. (...) http://hdl.handle.net/10985/10273 Study of the mechanical behavior and corrosion resistance of hydroxyapatite sol–gel thin coatings on 316 L stainless steel pre-coated with titania film SIDANE, Djahida; CHICOT, Didier; YALA, Sabeha; ZIANI, Salima; KHIREDDINE, Hafit; IOST, Alain; DECOOPMAN, Xavier In order to reinforce the clinical applications of hydroxyapatite (HAP) sol–gel coatings deposited onto 316 L stainless steel, we suggest the introduction of an intermediate thin layer of titania (TiO2) on the substrate. The titania sub-layer is introduced in order to improve both the corrosion resistance and the mechanical properties of the HAP/316 L stainless steel coated system. The twocoatings, HAP and TiO2,were studied separately and afterwards, compared with the bi-layered coating. A film without any cracks is obtained under the optimum conditions in terms of annealing temperature, dipping rate and aging effect. Microstructural, morphological and profilometry analysis revealed the non-stoichiometric carbonated porous nature of the hydroxyapatite coatings, which were obtained after annealing at 500 °C during 60 min in the atmosphere. The obtained TiO2 coatings exhibit a dense and uniform surface. Addition of TiO2 as sub-layer of the HAP coating tends to increase the homogeneity and the crystallinity rate as compared to the HAP one. The mechanical properties, i.e. hardness and elastic modulus, are determined by means of nanoindentation experiments and the adhesion between the coating and substrate is estimated by scratch tests. The corrosion behavior is evaluated by potentiodynamic cyclic voltammetry tests. As a main result, the values of the elastic modulus and hardness, respectively of 30 GPa and 2.5 GPa, are relatively high for the HAP–TiO2 bilayer coating. This result allows the use of such coated material as a replacement material for hard tissues. The adhesion strength increased from 2925 mN up to 6430 mN after the addition of the TiO2 intermediate film. According to the Tafel's analysis, the 316 L stainless steel specimens coated with both HAP and titania layers (ECorr = −234 mV, lCorr = 0.089 μA cm−2) present a better resistance than the HAP-coated specimens (ECorr= −460 mV, lCorr=0.860 μA cm−2). Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/10273 2015-01-01T00:00:00Z SIDANE, Djahida CHICOT, Didier YALA, Sabeha ZIANI, Salima KHIREDDINE, Hafit IOST, Alain DECOOPMAN, Xavier In order to reinforce the clinical applications of hydroxyapatite (HAP) sol–gel coatings deposited onto 316 L stainless steel, we suggest the introduction of an intermediate thin layer of titania (TiO2) on the substrate. The titania sub-layer is introduced in order to improve both the corrosion resistance and the mechanical properties of the HAP/316 L stainless steel coated system. The twocoatings, HAP and TiO2,were studied separately and afterwards, compared with the bi-layered coating. A film without any cracks is obtained under the optimum conditions in terms of annealing temperature, dipping rate and aging effect. Microstructural, morphological and profilometry analysis revealed the non-stoichiometric carbonated porous nature of the hydroxyapatite coatings, which were obtained after annealing at 500 °C during 60 min in the atmosphere. The obtained TiO2 coatings exhibit a dense and uniform surface. Addition of TiO2 as sub-layer of the HAP coating tends to increase the homogeneity and the crystallinity rate as compared to the HAP one. The mechanical properties, i.e. hardness and elastic modulus, are determined by means of nanoindentation experiments and the adhesion between the coating and substrate is estimated by scratch tests. The corrosion behavior is evaluated by potentiodynamic cyclic voltammetry tests. As a main result, the values of the elastic modulus and hardness, respectively of 30 GPa and 2.5 GPa, are relatively high for the HAP–TiO2 bilayer coating. This result allows the use of such coated material as a replacement material for hard tissues. The adhesion strength increased from 2925 mN up to 6430 mN after the addition of the TiO2 intermediate film. According to the Tafel's analysis, the 316 L stainless steel specimens coated with both HAP and titania layers (ECorr = −234 mV, lCorr = 0.089 μA cm−2) present a better resistance than the HAP-coated specimens (ECorr= −460 mV, lCorr=0.860 μA cm−2). http://hdl.handle.net/10985/10785 Propriétés mécaniques par indentation d’un film mince nanometrique de nitrure d’aluminium; Mechanical properties by indentation of aluminium nitride nanometric thin film ROUDET, Francine; CHICOT, Didier; DECOOPMAN, Xavier; IOST, Alain; BÜRGI, Juan; MOLLEJA, Javier Garcia; FEUGEAS, Jorge Les propriétés mécaniques des films minces sont généralement déterminées par nanoindentation pour éviter l’influence du substrat. En effet, nous savons que le substrat influence cette mesure dès lors que l’indenteur pénètre à plus de 10 % de l’épaisseur du film pour la dureté, ce chiffre pouvant être ramené à 1 % pour le module d’élasticité. Pour des films extrêmement minces pour lesquels la mesure directe des propriétés ne serait pas possible, l’application de modèles pour séparer la contribution du substrat de la mesure est alors nécessaire. Dans ce travail, la dureté et le module d’élasticité d’un film de nitrure d’aluminium de 250 nm d’épaisseur déposé par Magnetron Sputtering ont été déterminées par nanoindentation. Pour réduire l’influence de l’incertitude de l’épaisseur du film sur la détermination des propriétés mécaniques, nous proposons de masquer cette épaisseur dans les termes de lissage de plusieurs modèles et d’étudier leurs convergences. Concernant le module d’élasticité, nous avons observé que les valeurs suivaient une courbe typique en S entre deux asymptotes, une qui tend vers la valeur du module du film pour les très faibles profondeurs d’indentation et l’autre vers celle du substrat pour les plus fortes charges. Dans ces conditions, le modèle d’Antunes et al. utilisant le paramètre de Gao généralement utilisé dans de telles études, car ne faisant intervenir aucun coefficient de lissage, ne peut représenter correctement l’évolution des points expérimentaux. C’est pourquoi nous proposons d’utiliser une loi du type Avrami qui permet de bien prendre en compte ces deux tendances. Finalement, nous obtenons 10 GPa pour la dureté et 150 GPa pour le module d’élasticité en accord avec les données de la littérature.; The mechanical properties of thin film are usually determined by nanoindentation in order to circumvent the influence of the substrate. Indeed, it is recognized that the substrate interferes into the measurement when the indenter penetrates more than 10% of the film thickness for the hardness determination and 1% for the elastic modulus determination. For very thin films for which a direct measurement of the mechanical properties is not possible, models must be applied to separate the contribution of the substrate into the measurement. In this work, hardness and elastic modulus of aluminum nitride film of 250 nm of thickness deposited by Magnetron Sputtering have been determined by nanoindentation. In order to reduce the influence of the uncertainty of the film thickness value on the mechanical property determination, we suggest to introduce the thickness term into the fitting parameters of the different models and to study the convergence of these models. Concerning the elastic modulus, we observed that the experimental data varied following a typical S-curve between tow asymptotes, one which tends toward the value of the film modulus for very low indenter displacements and the other toward that of the substrate for the highest indentation loads. In these conditions, the model proposed by Antunes et al. using the Gao’s function in which no fitting parameters are involved cannot adequately represent the experimental data variation. That is the reason why we propose to apply similarly to the Avrami’s law which allows to take into account the tendencies at the two extremum. Finally, we obtained values close to 10 GPa and 150 GPa for the hardness and the elastic modulus, respectively, in accordance with the literature data. Thu, 01 Jan 2015 00:00:00 GMT http://hdl.handle.net/10985/10785 2015-01-01T00:00:00Z ROUDET, Francine CHICOT, Didier DECOOPMAN, Xavier IOST, Alain BÜRGI, Juan MOLLEJA, Javier Garcia FEUGEAS, Jorge Les propriétés mécaniques des films minces sont généralement déterminées par nanoindentation pour éviter l’influence du substrat. En effet, nous savons que le substrat influence cette mesure dès lors que l’indenteur pénètre à plus de 10 % de l’épaisseur du film pour la dureté, ce chiffre pouvant être ramené à 1 % pour le module d’élasticité. Pour des films extrêmement minces pour lesquels la mesure directe des propriétés ne serait pas possible, l’application de modèles pour séparer la contribution du substrat de la mesure est alors nécessaire. Dans ce travail, la dureté et le module d’élasticité d’un film de nitrure d’aluminium de 250 nm d’épaisseur déposé par Magnetron Sputtering ont été déterminées par nanoindentation. Pour réduire l’influence de l’incertitude de l’épaisseur du film sur la détermination des propriétés mécaniques, nous proposons de masquer cette épaisseur dans les termes de lissage de plusieurs modèles et d’étudier leurs convergences. Concernant le module d’élasticité, nous avons observé que les valeurs suivaient une courbe typique en S entre deux asymptotes, une qui tend vers la valeur du module du film pour les très faibles profondeurs d’indentation et l’autre vers celle du substrat pour les plus fortes charges. Dans ces conditions, le modèle d’Antunes et al. utilisant le paramètre de Gao généralement utilisé dans de telles études, car ne faisant intervenir aucun coefficient de lissage, ne peut représenter correctement l’évolution des points expérimentaux. C’est pourquoi nous proposons d’utiliser une loi du type Avrami qui permet de bien prendre en compte ces deux tendances. Finalement, nous obtenons 10 GPa pour la dureté et 150 GPa pour le module d’élasticité en accord avec les données de la littérature. The mechanical properties of thin film are usually determined by nanoindentation in order to circumvent the influence of the substrate. Indeed, it is recognized that the substrate interferes into the measurement when the indenter penetrates more than 10% of the film thickness for the hardness determination and 1% for the elastic modulus determination. For very thin films for which a direct measurement of the mechanical properties is not possible, models must be applied to separate the contribution of the substrate into the measurement. In this work, hardness and elastic modulus of aluminum nitride film of 250 nm of thickness deposited by Magnetron Sputtering have been determined by nanoindentation. In order to reduce the influence of the uncertainty of the film thickness value on the mechanical property determination, we suggest to introduce the thickness term into the fitting parameters of the different models and to study the convergence of these models. Concerning the elastic modulus, we observed that the experimental data varied following a typical S-curve between tow asymptotes, one which tends toward the value of the film modulus for very low indenter displacements and the other toward that of the substrate for the highest indentation loads. In these conditions, the model proposed by Antunes et al. using the Gao’s function in which no fitting parameters are involved cannot adequately represent the experimental data variation. That is the reason why we propose to apply similarly to the Avrami’s law which allows to take into account the tendencies at the two extremum. Finally, we obtained values close to 10 GPa and 150 GPa for the hardness and the elastic modulus, respectively, in accordance with the literature data.