Papers by Author: Pierre Caron

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Authors: Didier Locq, Pierre Caron, Catherine Ramusat, Rémy Mévrel
Abstract: Chromium-based alloys are considered as potential candidates for applications in hot sections of aero engine turbines due to their high melting point and their moderate density. Some ternary (Cr-Ni-Al) and quaternary (Cr-Ni-Al-Ti) alloys have been designed with the aim to induce precipitation of ordered strengthening precipitates and to promote the formation of a protective alumina scale. These alloys were cast using various techniques in order to assess their microstructural and mechanical properties and their oxidation resistance.
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Authors: Frédéric Diologent, Pierre Caron
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Authors: Florence Pettinari-Sturmel, Joël Douin, Didier Locq, Pierre Caron, Armand Coujou
Abstract: The mechanical behavior of the polycrystalline NR3 Ni-based superalloy has been investigated at the microscopic scale. The elementary deformation mechanisms have been analyzed using transmission electron microscope observations as well as in situ straining experiments. Under low stress and relatively low strain rate conditions, a large variety of shearing micromechanisms has been observed depending on the local microstructure and the local effective stress. The influence of the smallest precipitates on the creep behavior has been enlightened: they induce narrow channels which act as obstacle for the movement of the dislocations. In the case of the narrowest channel, the deformation can operate by the propagation of Shockley dislocations or else, by the only propagation of the leading partial resulting from the partial dislocation decorrelation. The occurrence of the observed micromechanisms has been quantitatively analyzed using a nodal dislocation dynamics simulation.
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Authors: Alain Jacques, Olivier Ferry, Frédéric Diologent, Pierre Caron, Pierre Bastie
Abstract: Variations in the lattice parameters of γ and γ' phases perpendicular to the [001] tensile axis were recorded in situ at ~10 minutes intervals using the Triple Axis Diffractometer of the High Energy (ID15) beamline at ESRF. Testing was carried out on an AM1 superalloy specimen with a raft microstructure at high temperature (1072°C) under load steps between 0 MPa and 300 MPa. These data were used to evaluate the Young modulus and the effective (Von Mises) stresses within the γ' rafts and γ corridors, as well the average plastic strain rates of each phase. The recorded stress data scatter was within the MPa range, and should be good enough to probe the elementary mechanisms of plasticity.
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Authors: Pierre Caron
Abstract: For several decades, strong efforts have been made in France in research and development activities dedicated to nickel-based superalloys for high-pressure disks and blades. New superalloys were designed then developed within cooperative research programmes bringing together research institutes, alloy producers and engine manufacturers. Continuous research activities were carried out on these alloys in order to perform detailed analyses of the relationships between process parameters, chemistry, microstructural features, deformation mechanisms and mechanical behavior. Typical studies are illustrated by examples outlining some recent results.
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Authors: Nicole Clément, Mustafa Benyoucef, M. Legros, Pierre Caron, Armand Coujou
Abstract: An in situ study of the plastic deformation of <001> single crystals of an industrial superalloy has been performed at 850 °C in a TEM to observe directly the micromechanisms which control the deformation under the actual temperature and stress conditions experienced by this material in aeroengines. A comparison between the creation and propagation modes of moving dislocations in the standard microstructure after annealing and the rafted microstructure after 20 h of creep at 1050°C evidence the important role of the width of the γ channels as well as the strength of the γ/γ’ interface in controlling the shearing events of γ’ channels.
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Authors: Pierre Caron, Frédéric Diogolent, Stefan Drawin
Abstract: The tensile yield strength of AM1 and MC-NG single crystal superalloys with a γ’ precipitate size close to 300 nm were compared within the 20-1050°C temperature range. The room temperature yield strength of the fourth generation MC-NG superalloy is about 200 MPa less than that of the AM1 first generation one. Inversely, at higher temperatures (T > 800°C), the tensile strength of MC-NG is higher than that of AM1. These results are discussed by taking into account the elementary deformation mechanisms and the respective strengths of the γ and γ’ phases. Experiments on a modified MC-NG alloy show that reinforcing the γ’ phase by increasing the contents of Ti and Ta is an efficient way to recover a higher tensile strength at low temperatures. Rhenium addition and increase of the γ’ solvus temperature are suggested to be beneficial for the high temperature tensile strength. Data published on various other single crystals are in agreement with these hypotheses.
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Authors: Mustafa Benyoucef, M. Legros, Armand Coujou, Pierre Caron, H.A. Calderón, Nicole Clément
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Authors: Christian R. Simon, M. Seiersten, Pierre Caron
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Authors: Florence Pettinari-Sturmel, Mustafa Benyoucef, Joël Douin, Pierre Caron, Didier Locq, Nicole Clément, Armand Coujou
Abstract: In situ straining of microsamples have been carried out at different temperatures in a transmission electron microscope (TEM) to provide information about the elementary micromechanisms, which control the deformation in Ni-based superalloys at the nano and microscopic scales. The obstacles to the propagation of the dislocations have been identified and quantified when possible. The strengthening effect in the -matrix channels and the shearing of ' precipitates have been chosen to illustrate some results deduced from moving dislocation analysis. A quantitative evaluation of the stresses acting on dislocations has been performed. The shearing process of the ' precipitates at 850°C has been precisely analysed.
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