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Patrice Berthod - One of the best experts on this subject based on the ideXlab platform.
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experimental and thermodynamic investigations regarding the effect of Chromium on the Carbides population in cast ni bal 0 4c 6ta xcr alloys with x varying from 0 to 50 wt
Calphad-computer Coupling of Phase Diagrams and Thermochemistry, 2018Co-Authors: Patrice Berthod, Zohra HimeurAbstract:Abstract Involving a particularly strong carbide-former metallic element, the tantalum Carbides are potentially very stable at elevated temperatures in term of volume fraction and morphology. The TaC phase represents a major strengthening way to allow cast Chromium-rich superalloys resisting mechanical stresses at elevated temperatures. They are exploited in recent high performance cobalt-based superalloys but seemingly not in nickel-Chromium refractory alloys. Earlier studies showed that the stability of TaC in Ni-Cr alloys is not so good as in the Co-Cr ones, and they evidenced that Chromium Carbides may compete with TaC in the formation of the Carbides population. A possible way to optimize the presence of TaC in Ni-Cr alloy may consist in rating the Chromium content to an ideal value but preliminary knowledge about the TaC dependence on the Cr content is compulsory. The aim of this work is precisely the investigation of the effect of the content in Chromium on the appearance and stability of the TaC phase in Ni-Cr alloys, by the means of thermodynamic calculations and real experiments in parallel. A global system Ni(bal.)-xCr-0.4C-6Ta compositions (with x varying from 0 to 50 wt%) was chosen. Thermodynamic calculations were performed to know the theoretic metallurgical states inside the considered x range. These theoretic results being dependent on the suitability of the used database, real experiments of verifications were also carried out for a selection of six alloys (x = 0, 10, 20, 30, 40 and 50 wt%). The alloys prepared by respecting these compositions were cast and isothermally exposed at high temperature (1400 and 1510 K), then subjected to metallographic characterization. For the used database the calculated results showed that no TaC should never appear whatever their Cr content, while TaC were really observed in the as-cast and aged versions of the alloys containing 20 wt%Cr and more, but never alone since Chromium Carbides were systematically also present. When the Cr content in the alloy is too low, the TaC are rare or even no present. This allowed concluding first that the database used for the calculations needs serious improvements, followed by tests with, as first criteria of quality, a good correspondence with the present experimental results. Second, the presence of Cr in quantity high enough is surprisingly compulsory to obtain TaC Carbides in quantity high enough, but it is no possible to avoid the appearance of Chromium Carbides. Obviously, other ways than Cr adjustments must be found to obtain TaC in nickel-based alloys as the single carbide phase and in quantity high enough to achieve high mechanical properties at high temperature.
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thermal properties of a cobalt based superalloy designed to be reinforced by titanium Carbides and Chromium Carbides
Materials Physics and Chemistry, 2018Co-Authors: Patrice Berthod, Mira KhairAbstract:In this study titanium Carbides were considered to strengthen alloys elaborated by classical foundry and displaying a polycrystalline structure. A model alloy, whose composition is Co(bal.)-25Cr-0.5C-1Ti (wt.%), serves as a kind of prototype to test the possibility of formation of TiC Carbides during solidification and the thermal resistance of these particles at elevated temperature. This alloy was synthesized by high frequency induction melting under inert atmosphere and was subjected to microstructure characterization, Differential Thermal Analysis and exposure at 1100°C for about two days. A dendritic cobalt-based matrix was obtained with, in the interdendritic spaces, Chromium Carbides and titanium Carbides. The melting point measured by DTA is slightly below 1300°C and the titanium Carbides well resisted to the exposure at high temperature. On-going tests carried out to assess the mechanical behavior at high temperature suggest rather high potential of creep resistance at 1100°C.
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use of thermogravimetry and thermodynamic calculations for specifying Chromium diffusion occurring in alloys containing Chromium Carbides during high temperature oxidation
Materials Chemistry and Physics, 2015Co-Authors: Patrice Berthod, Elodie ConrathAbstract:Abstract The Chromium diffusion is of great importance for the high temperature oxidation behaviour of the Chromium-rich Carbides-strengthened superalloys. These ones contain high Chromium quantities for allowing them well resisting hot corrosion by constituting and maintaining a continuous external scale of chromia. Knowing how Chromium can diffuse in such alloys is thus very useful for predicting the sustainability of their chromia-forming behaviour. Since Cr diffusion occurs through the external part of the alloy already affected by the previous steps of oxidation (decarburized subsurface) it is more judicious to specify this diffusion during the oxidation process itself. This was successfully carried out in this work in the case of a model chromia-forming nickel-based alloy containing Chromium Carbides, Ni(bal.)–25Cr–0.5C (in wt.%). This was done by specifying, using real-time thermogravimetry, the mass gain kinetic due to oxidation, and by combining it with the post-mortem determination of the Cr concentration profiles in subsurface. The values of DCr thus obtained for 1000, 1050 and 1100 °C in the alloy subsurface are consistent with the values obtained in earlier works for similar alloy's chemical compositions.
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microstructure evolution at high temperature of Chromium rich iron based alloys containing hafnium Carbides
International Journal of Materials Research, 2014Co-Authors: Elodie Conrath, Patrice BerthodAbstract:The high temperature behavior of three iron-based alloys rich in Chromium and containing HfC Carbides was studied in comparison with two ternary Fe-Cr-C alloys. All these alloys, contain 25 wt.% Cr, 0.25 or 0.50 wt.% C, and additionally 3.7 to 5.6 wt.% Hf for three of them. All alloys were produced in a foundry. They were exposed to air at 1200 degrees C for 46 h. Their microstructures in the as-cast state and after exposure to high temperature were characterized using X-ray diffraction, electron microscopy and image analysis. The alloys were also subjected to indentation tests in their as-cast states and in their aged states. The obtained microstructures are composed of a dendritic bcc iron-based matrix and of HfC Carbides. These Carbides are of two types: script-like eutectic Carbides mixed with matrix, and compact pre-eutectic Carbides. Some Chromium Carbides were additionally obtained in two of the three Hf-containing alloys. These microstructures have roughly evolved during the high temperature exposure: variations of the surface fraction of the Chromium Carbides and increase in the HfC surface fractions. Consequently, the hardness was more (ternary alloys) or less (Hf-containing alloys) decreased. The morphologies of the Carbides evolved: coalescence of the Chromium Carbides, coalescence and fragmentation of the HfC Carbides. The behavior of these alloys in oxidation at high temperature is perfectible. It is to be improved to allow the use of such alloys at high temperature.
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microstructure evolution in bulk and surface states of Chromium rich nickel based cast alloys reinforced by hafnium Carbides after exposure to high temperature air
Materials at High Temperatures, 2014Co-Authors: Patrice Berthod, E ConrathAbstract:AbstractThree alloys based on nickel, with a high level of Chromium (25 wt-%) and containing varied quantities of carbon, 0·25 and 0·50 wt-%, and hafnium, 3·7 and 5·6 wt-%, fabricated by casting, were subjected to a 46 h long exposure at 1200°C in dry industrial air. The aim of the work was to investigate the thermal stability of their carbide interdendritic network and to discover their general behaviour in high temperature oxidation. The volume fraction of the hafnium Carbides decreased slightly during high temperature exposure but their fragmentation was rather limited. In contrast, Chromium Carbides appeared in the two alloys, which initially contained exclusively HfC, and this may result in a decrease in their high temperature properties. The evolution of the Carbides appeared to be responsible for a moderate lowering of room temperature hardness. The behaviour of the three alloys during high temperature oxidation was very good, despite the unusually high content of hafnium. All were chromia-forming,...
J Vereecken - One of the best experts on this subject based on the ideXlab platform.
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AES–XPS study of Chromium Carbides and Chromium iron Carbides
Applied Surface Science, 1999Co-Authors: M Detroye, Francois Reniers, Claudine Buess-herman, J VereeckenAbstract:Abstract The nature of Chromium rich Carbides which precipitate at grain boundaries in steels is still not perfectly understood. We performed a multitechnique approach on model Chromium carbide and Chromium–iron carbide samples: Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and High Energy Electron Diffraction (HEED) were used to characterise the samples. Significant chemical shifts were observed for the Cr, Fe and C XPS peaks in the M 7 C 3 compound (M stands for metal), indicating unambiguously that the compound formed is a mixed iron–Chromium carbide.
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aes xps study of Chromium Carbides and Chromium iron Carbides
Applied Surface Science, 1999Co-Authors: M Detroye, Francois Reniers, Claudine Buessherman, J VereeckenAbstract:Abstract The nature of Chromium rich Carbides which precipitate at grain boundaries in steels is still not perfectly understood. We performed a multitechnique approach on model Chromium carbide and Chromium–iron carbide samples: Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and High Energy Electron Diffraction (HEED) were used to characterise the samples. Significant chemical shifts were observed for the Cr, Fe and C XPS peaks in the M 7 C 3 compound (M stands for metal), indicating unambiguously that the compound formed is a mixed iron–Chromium carbide.
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synthesis and characterisation of Chromium Carbides
Applied Surface Science, 1997Co-Authors: M Detroye, Francois Reniers, Claudine Buessherman, J VereeckenAbstract:Abstract This paper presents the synthesis and the characterisation of various Chromium carbide compounds. Thin Cr 23 C 6 films were deposited by reactive sputtering while Cr 7 C 3 films were formed by the carburisation of Chromium films in a CH 4 /H 2 atmosphere. Cr x C y powders were synthesised from various precursors (Cr, CrN, Cr 2 O 3 ) by reaction with CH 4 /H 2 at high temperature. The samples were characterised by AES, XRD and electron diffraction. The effects of the experimental parameters (gas composition, temperature, reaction time) on the purity, the phase formed and the composition of the product of reaction are examined and discussed.
S E Aghili - One of the best experts on this subject based on the ideXlab platform.
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microstructure and oxidation behavior of nicr Chromium Carbides coating prepared by powder fed laser cladding on titanium aluminide substrate
Ceramics International, 2020Co-Authors: S E Aghili, M Shamanian, Amini R Najafabadi, Ali Keshavarzkermani, Reza Esmaeilizadeh, Ehsan Marzbanrad, Ehsan ToyserkaniAbstract:Abstract In the present study, a NiCr–Cr3C2 powder mixture was prepared by mechanical alloying and then coated on titanium aluminide substrates by the powder-fed laser cladding process using a set of optimum parameters. The high temperature oxidation behavior of the substrate and coating was studied by isothermal annealing at 900 °C for 5 h. It was found that the microstructure of the coating is composed of γ solid solution with different Chromium carbide phases (Cr3C2, Cr7C3 and Cr23C6). The presence of different Chromium Carbides in the microstructure of coating can be attributed to the partial melting of primary Cr3C2 and the formation of non-equilibrium carbide phases during rapid cooling of laser cladding. The NiCr-Chromium carbide laser cladded coating samples showed superior oxidation resistance compared to the substrate. The oxidation mechanism of both coating and substrate follow the parabolic law, where the parabolic rate constant of the coating was 20% of that of the substrate at 900 °C. Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) and Grazing Angle X-Ray Diffraction (GAXRD) analysis revealed that the surface of the oxide layer formed on the NiCr-Chromium Carbides coating and the substrate is mostly composed of Cr2O3 and TiO2, respectively.
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investigation of powder fed laser cladding of nicr Chromium Carbides single tracks on titanium aluminide substrate
Optics and Laser Technology, 2019Co-Authors: S E Aghili, M ShamanianAbstract:Abstract In the present study, a Cr3C2 NiCr powder mixture was used to fabricate laser claddings on a titanium aluminide (TiAl) substrate. The effect of processing parameters, such as laser power (P), powder feeding rate (F) and scanning speed (S), were studied on the geometrical properties (height, width, dilution and wetting angle) of single-line claddings and their systematic correlation were predicted using the regression analysis method. The results indicated that the clad height showed a linear dependency on the P1.S−1.F0.85 parameter. Similarly, the width, wetting angle and penetration depth depicted a linear dependency on the P1.S−1.F−0.7, P0.8.S−0.7.F1 and P0.75.S0.5.F−1 parameters, respectively, while the dependency on dilution was S0.8.F−0.8. High values of the correlation coefficient were observed for all empirical dependencies. Finally, a processing window was developed for the laser cladding of the Cr3C2 NiCr powder mixture on the TiAl substrate. The microstructure analysis of the optimal cladding showed that the microstructure was covered with different Chromium Carbides (Cr3C2, Cr7C3 and Cr23C6), together with the Ni(Cr) solid solution. The microhardness of the optimal clad was found to be around 820 HV, which was higher than that of the titanium aluminide substrate (320 HV).
Sheela Singh - One of the best experts on this subject based on the ideXlab platform.
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Effect of Cr 2 AlC MAX phase addition on strengthening of Ni-Mo-Al alloy coating on piston ring: Tribological and twist-fatigue life assessment
Applied Surface Science, 2018Co-Authors: Deepak Davis, Bharat Bhooshan Panigrahi, Meenu Srivastava, Munisamy Malathi, Sheela SinghAbstract:The aim of the present study is to investigate the effect of Cr 2 AlC additions on the tribological properties of Piston Ring coated with Ni-Mo-Al alloy. For this Cr 2 AlC MAX phase was blended with Ni-Mo-Al alloy powder in different proportions (10 wt%, 20 wt% and 50 wt%) and coated on the stainless steel piston ring by Air Plasma Spraying (APS). During coating Cr 2 AlC MAX reacts with air and forms Cr 7 C 3 and Al 2 O 3 phases. The in-situ formation of Cr 7 C 3 and Al 2 O 3 was observed to strengthen the alloy. 20 wt% Cr 2 AlC additions to the Ni-Mo-Al alloy yields a good combination of properties, such as improved adhesion, hardness and wear resistance. Composite coating was found to be stable during the exfoliation test of the coated ring. Coating life cycles were found to be nearly doubled by MAX phase addition, as assessed through the twist-fatigue study. These improved properties could be attributed to the finely distributed oxides (alumina) and Chromium Carbides (Cr 7 C 3 ) within the coated layer, which were formed in-situ during plasma spraying.
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Effect of Cr2AlC MAX phase addition on strengthening of Ni-Mo-Al alloy coating on piston ring: Tribological and twist-fatigue life assessment
Applied Surface Science, 2018Co-Authors: Deepak Davis, Bharat Bhooshan Panigrahi, Meenu Srivastava, Munisamy Malathi, Sheela SinghAbstract:Abstract The aim of the present study is to investigate the effect of Cr 2 AlC additions on the tribological properties of Piston Ring coated with Ni-Mo-Al alloy. For this Cr 2 AlC MAX phase was blended with Ni-Mo-Al alloy powder in different proportions (10 wt%, 20 wt% and 50 wt%) and coated on the stainless steel piston ring by Air Plasma Spraying (APS). During coating Cr 2 AlC MAX reacts with air and forms Cr 7 C 3 and Al 2 O 3 phases. The in-situ formation of Cr 7 C 3 and Al 2 O 3 was observed to strengthen the alloy. 20 wt% Cr 2 AlC additions to the Ni-Mo-Al alloy yields a good combination of properties, such as improved adhesion, hardness and wear resistance. Composite coating was found to be stable during the exfoliation test of the coated ring. Coating life cycles were found to be nearly doubled by MAX phase addition, as assessed through the twist-fatigue study. These improved properties could be attributed to the finely distributed oxides (alumina) and Chromium Carbides (Cr 7 C 3 ) within the coated layer, which were formed in-situ during plasma spraying.
M Detroye - One of the best experts on this subject based on the ideXlab platform.
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AES–XPS study of Chromium Carbides and Chromium iron Carbides
Applied Surface Science, 1999Co-Authors: M Detroye, Francois Reniers, Claudine Buess-herman, J VereeckenAbstract:Abstract The nature of Chromium rich Carbides which precipitate at grain boundaries in steels is still not perfectly understood. We performed a multitechnique approach on model Chromium carbide and Chromium–iron carbide samples: Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and High Energy Electron Diffraction (HEED) were used to characterise the samples. Significant chemical shifts were observed for the Cr, Fe and C XPS peaks in the M 7 C 3 compound (M stands for metal), indicating unambiguously that the compound formed is a mixed iron–Chromium carbide.
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aes xps study of Chromium Carbides and Chromium iron Carbides
Applied Surface Science, 1999Co-Authors: M Detroye, Francois Reniers, Claudine Buessherman, J VereeckenAbstract:Abstract The nature of Chromium rich Carbides which precipitate at grain boundaries in steels is still not perfectly understood. We performed a multitechnique approach on model Chromium carbide and Chromium–iron carbide samples: Auger Electron Spectroscopy (AES), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and High Energy Electron Diffraction (HEED) were used to characterise the samples. Significant chemical shifts were observed for the Cr, Fe and C XPS peaks in the M 7 C 3 compound (M stands for metal), indicating unambiguously that the compound formed is a mixed iron–Chromium carbide.
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synthesis and characterisation of Chromium Carbides
Applied Surface Science, 1997Co-Authors: M Detroye, Francois Reniers, Claudine Buessherman, J VereeckenAbstract:Abstract This paper presents the synthesis and the characterisation of various Chromium carbide compounds. Thin Cr 23 C 6 films were deposited by reactive sputtering while Cr 7 C 3 films were formed by the carburisation of Chromium films in a CH 4 /H 2 atmosphere. Cr x C y powders were synthesised from various precursors (Cr, CrN, Cr 2 O 3 ) by reaction with CH 4 /H 2 at high temperature. The samples were characterised by AES, XRD and electron diffraction. The effects of the experimental parameters (gas composition, temperature, reaction time) on the purity, the phase formed and the composition of the product of reaction are examined and discussed.