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Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 880-891, October 21–24, 2019,
... Abstract The Alloys-by-Design approach, involving large-scale CALPHAD calculations to search a compositional range, has been used to isolate a suitable nickel-based superalloy for additive manufacturing (AM) by optimizing the trade-off between processability and increasing strength. This has...
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The Alloys-by-Design approach, involving large-scale CALPHAD calculations to search a compositional range, has been used to isolate a suitable nickel-based superalloy for additive manufacturing (AM) by optimizing the trade-off between processability and increasing strength. This has been done in response to the limited focus on development of new superalloys designed to overcome the limitations of the AM process, specifically the high defect density of parts made from high-performance alloys. Selected compositions have been made using gas atomization, and laser powder-bed fusion AM trials were performed. The resulting properties were evaluated in the as-processed, heat treated and thermally exposed conditions. The assessment, combined with characterization techniques including scanning electron microscopy and atom probe tomography, rationalizes a temperature capability up to and above 850 °C, and demonstrate the opportunity to develop alloys with properties beyond the current state of the art.
Proceedings Papers
AM-EPRI2010, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Sixth International Conference, 386-392, August 31–September 3, 2010,
... for higher-temperature applications. Using the CALPHAD method, a prototype alloy (Ni-23Co-18Cr-8W-4Al-0.1C) was developed by eliminating Ti, Nb, and Ta to improve hot-workability while maintaining strength. The resulting alloy demonstrates twice the creep strength of Nimonic 263, with an estimated 10 5 h...
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A new Ni-base superalloy has been developed for Advanced Ultra Super Critical (A-USC) power plants operating above 750°C, targeting reduced CO 2 emissions through improved efficiency. While existing research focuses on 700°C-class materials, this study presents a novel alloy design for higher-temperature applications. Using the CALPHAD method, a prototype alloy (Ni-23Co-18Cr-8W-4Al-0.1C) was developed by eliminating Ti, Nb, and Ta to improve hot-workability while maintaining strength. The resulting alloy demonstrates twice the creep strength of Nimonic 263, with an estimated 10 5 h steam turbine creep resistance temperature of 780°C, marking a significant advancement in A-USC material capabilities.
Proceedings Papers
AM-EPRI2010, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Sixth International Conference, 423-435, August 31–September 3, 2010,
... Abstract A modified version of Alloy 706, designated FENIX-700, was developed using the CALPHAD method to improve high-temperature stability above 700°C. The new alloy features reduced Nb and increased Al content, relying on γ' (Ni 3 Al) strengthening while eliminating γ'' (Ni 3 Nb), δ, and η...
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A modified version of Alloy 706, designated FENIX-700, was developed using the CALPHAD method to improve high-temperature stability above 700°C. The new alloy features reduced Nb and increased Al content, relying on γ' (Ni 3 Al) strengthening while eliminating γ'' (Ni 3 Nb), δ, and η phases. This modification improved both creep temperature capability (from 650°C to 700°C) and segregation properties. Successful manufacturing trials included a 760 mm² forging shaft using triple melt processing and a 1050 mm ESR ingot, demonstrating industrial viability. The study also explores compatible Ni-base welding materials for joining FENIX-700 to 12% Cr ferritic steel in 700°C class steam turbine applications.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 924-932, October 15–18, 2024,
... the ability of a liquid to backfill the interdendritic regions during solidification. By using computational fluid dynamics (CFD) and CALPHAD (Calculation of Phase Diagrams) analyses, the FRI can evaluate the dendritic network's flow resistance, thereby predicting the cracking susceptibility of different...
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Solidification cracking (SC) is a defect that occurs in the weld metal at the end of the solidification. It is associated with the presence of mechanical and thermal stresses, besides a susceptible chemical composition. Materials with a high solidification temperature range (STR) are more prone to the occurrence of these defects due to the formation of eutectic liquids wetting along the grain boundaries. The liquid film collapses once the structure shrinks and stresses act during the solidification. Thus, predicting the occurrence of SC before the welding process is important to address the problem and avoid the failure of welded components. The nuclear power industry has several applications with dissimilar welding and SC-susceptible materials, such as austenitic stainless steels, and Ni-based alloys. Compositional optimization stands out as a viable approach to effectively mitigate SC in austenitic alloys. The integration of computational modeling into welding has significantly revolutionized the field of materials science, enabling the rapid and cost-effective development of innovative alloys. In this work, a SC resistance evaluation is used to sort welding materials based on a computational fluid dynamic (CFC) model and the alloy's chemical composition. An index named Flow Resistance Index (FRI) is used to compare different base materials and filler metals as a function of dilution. This calculation provides insights into the susceptibility to SC in dissimilar welding, particularly within a defined dilution range for various alloys. To assess the effectiveness of this approach, the relative susceptibility of the materials was compared to well-established experimental data carried out using weldability tests (Transvarestraint and cast pin tear test). The FRI calculation was programmed in Python language and was able to rank different materials and indicate the most susceptible alloy combination based on the dilution and chemical composition.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 1469-1475, October 21–24, 2019,
... of both phases and the Gibbs free energies of other competing phases in the system. The Gibbs free energy is a combination of the energy of formation of the phase and its entropy representing the temperature dependent part of the Gibbs free energy [9]. The so called CALPHAD method is able to predict Gibbs...
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Either at higher temperatures or when a certain alloying element content is exceeded, γ-TiAl alloys contain the β phase (bcc) or its ordered derivate β o (B2). The relatively soft β phase can facilitate hot deformation, but β o is detrimental for creep strength and ductility. Thus, knowledge about β o →β phase transformation is desirable. Surprisingly, for the binary Ti-Al system it is under discussion whether the ordered β o phase exists. Also, the effect of alloying elements on the β phase ordering is still unclear. In the present work the ordering of the β phase in binary Ti-(39,42,45)Al and ternary Ti-42Al-2X alloys (X=Fe, Cr, Nb, Ta, Mo) which was experimentally investigated by neutron and high energy X-ray diffraction is compared with the results of first principles calculations using density functional theory. Except for Cr the experimentally determined and the predicted behavior correspond.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 592-599, October 15–18, 2024,
... the microstructure obtained by a particular processing step or calculate the properties deriving from a set of microstructural features. It should be noted that ICME methodology can be universally applicable to the rapid design and deployment of a variety of material systems. CALPHAD Database for Nb Superalloy...
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The aspiration to deploy Nb-based alloys as viable upgrade for Ni-based superalloys is rooted in their potential for superior performance in high-temperature applications, such as rocket nozzles and next-generation turbines. However, realizing this goal requires overcoming formidable design hurdles, including achieving high specific strength, creep resistance, fatigue, and oxidation resistance at elevated temperatures, while preserving ductility at lower temperatures. Additionally, the requisite for alloy bond-coatings, to ensure compatibility with coating materials, further complicates the design process. QuesTek Innovations has its Integrated Computational Materials Engineering (ICME) technologies to design a superior performance high-temperature Nb-based superalloy based on solid solution and precipitation strengthening. Additionally, utilizing a statistical learning method from very limited available data, QuesTek engineers were able to establish physics-based material property models, enabling accurate predictions of equilibrium phase fraction, DBTT, and creep properties for multicomponent Nb alloys. With the proven Materials by Design methodology under the ICME framework, QuesTek successfully designed a novel Nb superalloy that met the stringent design requirements using its advanced ICMD materials modeling and design platform.
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 768-777, October 11–14, 2016,
.... This study utilized JMatPro [8], a thermodynamics and kinetics package based on the CALculation of PHAse Diagrams (CALPHAD) method and databases. CALPHAD looks at the free energy contributions of each element in the mixture and their potential to form a wide array of phases. In thermodynamic equilibrium...
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Due to a high degree of mixing between substrate and weld deposit, fusion welding of dissimilar metal joints functionally produce new, uncharacterized alloys. In the power generation industry, such mixing during the application of cobalt-based hardfacing has led to a disconcerting number of failures characterized by the hard overlay welds disbonding. Investigations into this failure mechanism point to the unknown alloy beneath the surface of the hardfacing layer transforming, hardening, and becoming brittle during service. This research describes a methodology for exploring a chemical space to identify alloy combinations that are expected to be safe from deleterious phase formation. Using thermodynamic modeling software and a stepped approach to potential chemistries, the entire phase stability space over the full extent of possible mixing between substrate and weld material can be studied. In this way diffusion effects – long term stability – can also be accounted for even in the case where mixing during application is controlled to a low level. Validation of predictions specific to the hardfacing system in the form of aged weld coupons is also included in this paper. Though the application of this methodology to the hardfacing problem is the focus of this paper, the method could be used in other weld- or diffusion- combinations that are expected to operate in a high temperature regime.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 235-246, October 15–18, 2024,
... alloy series using a CM 1610 Bottom Loader furnace for a total 110 x 1 h cycles (cooled to 25°C for 20 min after each 1100°C exposure). Weight change measurements were performed with an analytical balance (±0.01 mg) Lastly, the use of both CALPHAD (Thermo-Calc/DICTRA) [38] and a flux-based approach...
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During the last decades, new generations of Ni-based superalloys have emerged with judiciously controlled chemistries. These alloys heavily rely on the addition of refractory elements to enhance their mechanical properties at elevated temperatures; however, a clear interpretation of the influence of these minor-element additions on the alloy's high-temperature oxidation behavior is still not well understood, particularly from the standpoint of predicting the transition from internal to external alumina formation. In this context, the present investigation describes a systematic study that addresses the intrinsic effects that minor element additions of Nb, Ta, and Re have on the oxidation behavior of alumina-scale forming γ-Ni alloys. By combining a novel simulation approach with high-temperature oxidation experiments, the present study evidences the generally positive effect associated with 2 at. % addition of Ta and Re as well as the detrimental consequences of Nb additions on the 1100 °C oxidation of (in at. %) Ni-6Al-(0,4,6,8)Cr alloys.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 662-668, October 15–18, 2024,
... enrichment, Corros. Sci. 176 (2020), 108937 [6] S. Ida, K. Hoshizaki, T. Kaneko, Xi. Nan, N. Sekido, K. Yoshimi, Off-stoichiometry and molybdenum substitution effects on elastic moduli of B1-type titanium carbide, Scientific Reports 13 (2023), 13631 [7] A. van de Walle et al. CALPHAD: Computer Coupling...
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Titanium carbide (TiC) have a wide off-stoichiometric composition when in equilibrium with the metallic phase. In this case, the off-stoichiometric effect allows the substitution of other transition metals (TM) at the Ti site and vacancy formation at the C site. It leads to changes in the material properties of TiC. Therefore, it is important to investigate the change of material properties with the off-stoichiometric effect. In this study, the elastic properties of (Ti, TM)C x were focused on. To investigate the change of elastic properties with various transition metals substitution, elastic properties were evaluated by first-principles calculations. From the calculation, it was suggested that bulk modulus is controlled by the 1st and 2nd nearest neighbor bond, but shear modulus is mainly affected by only the 1 st nearest neighbor bond. Therefore, it was indicated that proper control of the fraction of transition metals and vacancy could be possible for designing (Ti.TM)C x with high strength and toughness.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 1126-1137, October 15–18, 2024,
... strengthened alloys [2,21]; and 5) Al and Ti additions to provide additional precipitation strengthening by g , sinks for He+ and improvement in corrosion resistance to molten chloride salt through formation of stable a-Al2O3 scale. In this manuscript, the CALPHAD assessment is not included. The relevant...
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An attempt is being made to develop novel Ni-Mo-W-Cr-Al-X alloys with ICME approach with critical experimental/simulations and processing/microstructural characterization/property evaluation and performance testing has been adopted. In this work, based on thermodynamic modeling five alloy compositions with varying Mo/W and two alloys with high tungsten modified with the addition of Al or Ti were selected and prepared. The newly developed alloys were evaluated for their response to thermal aging in the temperature range of 700 to 850 °C and corrosion in the KCl-NaCl-MgCl 2 salt under suitable conditions. Thermally aged and post-corrosion test samples were characterized to ascertain phase transformations, microstructural changes and corrosion mechanisms. Al/Ti modified alloys showed significant change in hardness after 400 hours aging at 750°C, which was found to be due to the presence of fine γ’/γ” precipitates along with plate-shaped W/Mo-rich particles. These alloys show comparable molten salt corrosion resistance as commercial alloys at 750°C for 200-hour exposures. The good corrosion behavior of these alloys may be attributed to the formation of a protective multicomponent Al-or Ti-enriched oxide as well as the unique microstructure.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 371-381, October 22–25, 2013,
... Re-assessment of the Ternary System Al-Cr-Ni , Calphad, Vol. 25, No. 2 (2001), pp. 279-298. [13] Chakravorty, S., and West, D. R. F., The Constitution of the Ni-Al-Ru System , J. Mater. Sci., Vol. 21, (1986), pp. 2721-2730. [14] Zhu, J., Zhang, C., Cao, W., et al,, Experimental Investigation...
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Coatings are an essential part of the materials system to protect the turbine blades from oxidation and corrosive attack during service. Inter-diffusion of alloying elements between a turbine blade substrate and their coatings is a potential concern for coated turbine blades at ever increasing operating temperatures because this can cause the formation of undesirable Secondary Reaction Zones (SRZs), which may degrade the mechanical properties of coated Ni-based superalloys. Understanding the effects of each element on the SRZ formation is essential in order to understand both the mechanism and inter-diffusion behaviour between coatings and substrates. In this research, a number of simpler aluminized ternary Ni-Al-X (where X is Co, Cr, Re, Ru or Ta) alloys were investigated in order to elucidate the separate effects of each element on the microstructural evolution, especially at the coating/substrate interface. The aluminized ternary alloys developed distinctive diffusion zones, depending on the third alloy element, ‘X’. Specifically, it has been found that both Ni-Al-Re and Ni-Al-Ta alloys developed a continuous SRZ-like diffusion layer. This diffusion zone persisted in the Ni-Al-Re alloys after high temperature exposure, indicating that Re has a stronger effect on SRZ formation than Ta.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 897-908, October 15–18, 2024,
...] Pillai, R., T. Galiullin, A. Chyrkin, W.J. Quadakkers, Methods to increase computational efficiency of CALPHAD-based thermodynamic and kinetic models employed in describing high temperature material degradation, CALPHAD, Vol. 53 (2016) pp. 62-71. [13] Thermo-Calc, Thermo-Calc Software TCNi11/Ni-alloys...
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There is a critical lack of data on the mechanical behavior of candidate structural materials for advanced nuclear reactors under molten halide salt environments. Limited legacy data from the molten salt reactor experiment (MSRE) program showed a significant reduction in creep rupture strength of a Ni-base alloy in molten fluoride salt. With ongoing efforts to commercialize different molten salt reactor concepts, the industry can considerably benefit from quantitative information on the impact of molten halide salts on the engineering properties such as creep and fatigue strength of materials of interest. The present work aims to assess the role of molten salt corrosion on the creep behavior of three alloys 316H, 617 and 282 at 650-816 °C. Creep tests were conducted in fluoride (FLiNaK) and chloride (NaCl-MgCl 2 ) salts. Initial results from the ongoing testing will be presented which suggest that the molten salt environment caused a 25-50% reduction in creep rupture lifetime compared to air exposures. Physics-based corrosion and creep models were employed to gain some insights into the potential degradation mechanisms.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 1363-1371, October 22–25, 2013,
... (1991), 151-159. [4] Y. Tsukada, Y. Murata, T. Koyama, and M. Morinaga, Mater. Trans. 49(2008), 484-488. [5] Y. Murata, T. Koyama, M. Morinaga, and T. Miyazaki, ISIJ Int. 42 (2002), 1423 1429. [6] N. Saunders and A. P. Miodownik, CALPHAD, Pergamon, (1998). [7] V. Thomas Paul, S. Saroja, and M...
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Prediction of long-term creep strength is an important issue for industrial plants operated at elevated temperatures, although the creep strength of high Cr ferritic steels depends on their microstructural evolution during creep. The state of microstructure in metallic materials can be expressed as numerical values based on a concept of system free energy. In this study, in order to evaluate long term creep strength of 9Cr ferritic steel containing B, change in the system free energy during creep of the steel is evaluated as the sum of chemical free energy, strain energy and surface energy, which are obtained by a series of experiments, i.e., chemical analysis using extracted residues, X-ray diffraction, and scanning transmission electron microscopy. The system free energy decreases with creep time. Change in the energy is expressed quantitatively as a numerical formula using the rate constants which depend on applied stress. On the basis of these facts, long term creep strength of the steel can be evaluated at both 948K(675°C) and 973K(700 °C).
Proceedings Papers
AM-EPRI2016, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Eighth International Conference, 486-493, October 11–14, 2016,
...] Murata, Y., Koyama, T., Morinaga, M. and Miyazaki, T., Prediction of the Laves Phase Morphology in Fe-Cr-W-C Quaternary Steels with the Aid of System Free Energy Concept , ISIJ Int. 42 (2002), pp. 1423 1429. [6] Saunders, N. and Miodownik, A.P., CALPHAD, Pergamon, (Oxford, 1998). [7] Thomas P.V., Saroja...
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In order to evaluate long term creep strength of modified 9Cr ferritic steels, the system free energy of creep ruptured specimens at both 650 and 700 °C is evaluated as the sum of chemical free energy, strain energy and surface energy, which are obtained by a series of experiments, i.e., chemical analysis using extracted residues, X-ray diffraction, and scanning transmission electron microscopy. Change ratio of the system free energy and creep stress showed the relationship with one master curve irrespective of creep conditions, indicating that the steel ruptures when the applied stress exceeds a limited stress depending on the microstructural state expressed by the change ratio of system free energy. Furthermore, it was found that dominant factor of the change ratio was the chemical free energy change. On the basis of these results, long term creep strength of the steel was evaluated at 700 °C, for example, 19MPa at 700 °C after 10 5 h. It is concluded that long term creep strength of modified 9Cr ferritic steels can be predicted by the system free energy concept using the ruptured specimens with various creep conditions.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 1408-1417, October 21–24, 2019,
... at Elevated Temperatures J. Japan Inst. Metals, Vol. 75, No,4, 2011, pp.265-273. 1416 [3] E.Kozeschnik, Thermo-kinetics based materials modeling with MatCalc-Functionality and integration , 2014. [4] Taichi Abe, Kiyoshi Hashimoto, Thermodynamic Calculations using CALPHAD Method and their Applications...
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The precipitation behavior of various phases in austenitic heat-resistant model steels, including the Fe 2 Nb Laves phase (C14 structure) on grain boundaries (GB) and grain interiors (GI), and the Ni 3 Nb metastable γ“ phase and stable δ phase on GI, was investigated through experimental study at different temperatures and thermokinetic calculation. The steel samples were prepared by arc melting followed by 65% cold rolling. Subsequently, the samples were solution treated within the γ single-phase region to control the grain size to approximately 150 μm. Aging of the solution-treated samples was carried out at temperatures ranging from 973 K to 1473 K for up to 3600 hours. Microstructural observations were conducted using FE-SEM, and the chemical compositions of the γ matrix and precipitates of Laves and δ phases were analyzed using EPMA. The precipitation modeling was performed using MatCalc software, utilizing a thermodynamic database constructed by our research group to calculate the chemical potential of each phase. Classical nucleation theory was applied for nucleation, while the SFFK model was employed for the growth and coarsening stages. Distinct phases were defined for grain boundary and grain interior Laves phase, with all precipitates assumed to have spherical morphology in the calculations. The precipitation start time was defined as the time when the precipitate fraction reached 1%. Experimental results indicated that above 973 K, Laves phase nucleation primarily occurred on grain boundaries before extending into the grain interior, with the nose temperature located around 1273 K. To replicate the experimentally determined Time-Temperature-Precipitation (TTP) diagram, interaction parameters among elements were adjusted. Additionally, by introducing lower interfacial energy between the γ matrix and Laves phase, the TTP diagram was successfully reproduced via calculation, suggesting relative stability at the interface.
Proceedings Papers
AM-EPRI2019, 2019 Joint EPRI – 123HiMAT International Conference on Advances in High-Temperature Materials, 227-234, October 21–24, 2019,
.... The following phases were selected independently for calculation: BCC, FCC, M23C6 carbide, Laves phase (Fe2(W,Mo) (C14). The particle coarsening kinetic was calculated using Prisma-software on the base Calphad Database Calculation with the kinetic MOBFE1 and the thermodynamic TCFE6 databases. The model...
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The size and distribution of the Laves phase particles in a 9.85Cr-3Co-3W-0.13Mo-0.17Re- 0.03Ni-0.23V-0.07Nb-0.1C-0.002N-0.008B steel subjected to creep rupture test at 650°C under an applied stresses of 160-200 MPa with a step of 20 MPa were studied. After heat treatment consisting of normalizing of 1050°C and tempering of 770°C, M 23 C 6 and Fe 3 W 3 C carbides with the mean sizes of 67±7 and 40±5 nm, respectively, were revealed along the boundaries of prior austenite grains and martensitic laths whereas round NbX carbonitrides were found within martensitic laths. During creep metastable Fe 3 W 3 C carbides dissolved and the stable Laves phase particles precipitated; volume fraction of Laves phase increases with time. The Laves phase particles nucleated on the interfacial boundaries Fe 3 W 3 C/ferrite during first 100 h of creep and provided effective stabilization of tempered martensitic lath structure until their mean size less than 150 nm.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 412-423, October 22–25, 2013,
... and Phase Equilibrium Software from the National Physical Laboratory . CALPHAD. June 2002, Vol. 26, 2, pp. 229-271. [4] Saunders, N, Phase Diagram Calculations for Ni-based Superalloys. [ed.] R. D. Kissinger, et al: The Minerals, Metals & Materials Society, Warrendale, PA 150867528, USA, 1996. Proceedings...
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A combination of creep tests, ex-service blade samples, thermodynamic equilibrium calculations, combined thermodynamic and kinetic calculations, image analysis, chemical composition mapping and heat treatments have been conducted on PWA1483 to determine if microstructural rejuvenation can be achieved when taking the presence of oxidation coatings into account as part of a blade refurbishment strategy. The work has shown that the γ′ morphology changes during creep testing, and that through subsequent heat treatments the γ′ microstructure can be altered to achieve a similar γ′ size and distribution to the original creep test starting condition. Thermodynamic equilibrium calculations have been shown to be helpful in determining the optimum temperatures to be used for the refurbishment heat treatments. The interaction of oxidation resistant coatings with the alloy substrate and refurbishment process have been explored with both experimental measurements and coupled thermodynamic and kinetic calculations. The predictive nature of the coupled thermodynamic and kinetic calculations was evaluated against an ex-service blade sample which had undergone refurbishment and further ageing. In general there was good agreement between the experimental observations and model predictions, and the modelling indicated that there were limited differences expected as a result of two different refurbishment methodologies. However, on closer inspection, there were some discrepancies occurring near the interface location between the coating and the base alloy. This comparison with experimental data provided an opportunity to refine the compositional predictions as a result of both processing methodologies and longer term exposure. The improved model has also been used to consider multiple processing cycles on a sample, and to evaluate the coating degradation between component service intervals and the consequences of rejuvenation of the blade with repeated engine exposure. The results from the experimental work and modelling studies potentially offer an assessment tool when considering a component for refurbishment.
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 1093-1103, October 22–25, 2013,
... steels , Energy Materials (2006) Vol. 1(1), pp. 49-57. [9] Danielsen, H.K.; Hald, J.: A thermodynamic model of the Z-phase Cr(V, Nb)N , Calphad 31, 2007, pp. 505-514. [10] Kimura, K; Toda, Y; Kushima, H; Sawada, K.: Creep strength of high chromium steel with ferrite matrix , International journal...
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The recently developed 12%Cr steel VM12-SHC is characterized by very good creep properties at temperatures up to 620°C. This new material development exhibits an excellent oxidation resistance in steam atmospheres at the typical application temperature but also at temperatures up to 650°C. In comparison to the existing 9% Cr grades T/P91 and T/P92, VM12-SHC steel opens due to its excellent oxidation behavior, new possibilities for its application as a heat exchanger boiler component. It was found that outside its application temperature range VM12-SHC also shows, as all 9-12%Cr steels, the appearance of the so called Z-phase. This effect was investigated to understand its influence on creep properties of this class of ferritic/martensitic steels aiming at controlling the microstructure stabilities for future grade developments. Creep testing has been carried out in the temperature range between 525°C and 700°C. Selected crept specimens have been investigated using light optical microscopy, SEM with EDX and TEM. In this study, the oxidation behavior of a number of typical martensitic 9-12%Cr steels was compared with the newly developed 12% Cr steel VM12-SHC. The compositions and morphologies of oxide scales formed after 5000 h exposure steels in simulated steam environments as function of temperature were characterized by light optical metallography and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX).
Proceedings Papers
AM-EPRI2013, Advances in Materials Technology for Fossil Power Plants: Proceedings from the Seventh International Conference, 1116-1126, October 22–25, 2013,
... % Cr steels. VGB Power Tech (2009):68. 1125 [5] Danielsen HK, Hald J. "A thermodynamic model of the Z-phase Cr(V, Nb)N". CALPHAD-Computer Coupling of PHase Diagrams and Thermochemistry (2007);31:505. [6] Liu F, Andrén H-O. "Initial study on Z-phase strengthened 9-12% Cr steels by atom probe tomography...
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Two Z-phase strengthened test steels with similar chemical composition were studied. The main difference in composition is the addition of 1 wt% Cu into one of the steels (referred to as “ZCu”). Mechanical testing was performed. The impact strength is very different: 3 J vs. 46.3 J, for the original and the Z-Cu steel, respectively. In the original steel that contains no Cu, much more Laves-phase (Fe 2 (W,Mo)) precipitates had formed along the prior austenite grain boundaries than in the steel with Cu addition. This is believed to be the reason for the difference in impact strength. Furthermore, the Cu addition also influenced the morphology of Laves-phase precipitates; fine rod-shaped instead of coarse equiaxed Laves-phase particles were observed in Z-Cu steel in comparison to the original steel. No partitioning of Cu into the Laves-phase particles was detected by using atom probe tomography (APT). The main function of Cu seems to be the formation of Cu precipitates that act as nucleation site for Laves-phase.
Proceedings Papers
AM-EPRI2024, Advances in Materials, Manufacturing, and Repair for Power Plants: Proceedings from the Tenth International Conference, 13-22, October 15–18, 2024,
.... Kozeschnik, Modeling Solid-State Precipitation , Momentum Press (2013). [3] P. Schaffnit, C. Stallybrass, J. Konrad, F. Stein and M. Weinberg, A Scheil-Gulliver model dedicated to the solidification of steel , CALPHAD 48 (2015) pp. 184-188. 21 [4] I. Tarigan, K. Kurata, N. Takata, T. Matsuo and M. Takeyama...
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For the safe operation of high temperature equipment, it is necessary to ensure creep rupture ductility of the components from the viewpoint of notch weakening. In this study, the effect of heat treatment conditions on creep rupture ductility was evaluated and its underlying metallurgical mechanism was investigated with using a forged Ni-based superalloy Udimet520. In order to improve the creep rupture ductility without lowering the creep rupture strength, it is important to increase both intragranular strength and intergranular strength in a balanced manner. For this purpose, it was clarified that 1) secondary γ' phase within grains should be kept fine and dense, 2) grain boundaries should be sufficiently covered by M 23 C 6 carbide by increasing its phase fraction, and 3) tertiary γ' phase within grains should be redissolved before the start of creep. To obtain such a precipitate state, it is essential to appropriately select the cooling rate after solution treatment, stabilizing treatment and aging treatment conditions.
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