Diffusion Coefficient Of Cr Research Articles

Early-stage diffusion and oxidation behavior of Cr-Nb coated Zr alloy accident tolerant fuel cladding materials at 1200°C–1500°C

Although the Cr-coated Zr alloys are considered as the most promising accident tolerant fuel cladding materials in recent years, the Cr-Zr interdiffusion problem is a major obstacle for the widely used of the Cr coating. In this study, Cr-Nb coated Zr alloy samples were prepared by magnetron sputtering. The Nb layer was designed as a barrier layer to retard the Cr-Zr interdiffusion. By using a fast-in and fast-out equipment, short time annealing was conducted in argon environment to study the coating evolution in high temperature environment. Results show that the Nb coating can retard the inward diffusion of Cr because of the low diffusion coefficient of Cr in the Nb layer. However, the complete miscibility between Nb and Zr lead to the fast consumption of the Nb coating. After 10 min annealing at 1200 °C, the 2.5 μm Nb coating disappeared, and a Cr-Zr-Nb mixed phase formed between the residual Cr coating and Zr substrate. The early-stage microstructure evolution of the sample was analyzed, and the barrier effect of the Nb coating was summarized.

Introducing concepts of estimating tracer and intrinsic diffusion coefficients in a ternary system: a case study in the FCC Fe-Mn-Cr solid solution

ABSTRACT Estimating tracer and intrinsic diffusion coefficients following the diffusion couple method with systematic composition variation can be challenging because of the diffusion paths’ serpentine or double serpentine nature on the Gibbs triangle. Moreover, the possibility of estimating these diffusion coefficients from a single diffusion profile can have immense benefits. We have demonstrated four ways of estimating tracer and impurity diffusion coefficients in the FCC Fe-Mn-Cr solid solution: (i) We have shown that these can be estimated directly at the Kirkendall marker plane from a single conventional ternary diffusion profile. (ii) We have, for the first time, demonstrated that the estimation at the intersection of a conventional ternary and constrained pseudo-binary diffusion path is helpful for systematically generating composition-dependent tracer diffusion coefficients. (iii) We have followed the Kirkaldy-Lane method for estimating these diffusion coefficients at the intersection of two conventional ternary diffusion couples (for comparison of the data measured by new methods), although for data generation at random compositions. This was proposed a long time ago but practised occasionally. It helps to compare with the estimated data following other methods. (iv) Additionally, we have estimated the impurity diffusion coefficients of Cr and Mn in Fe following the Hall method, which helps in understanding the variation of the diffusion coefficients in Fe-Mn-Cr alloys compared to pure Fe. The sensitivity of data estimation following different methods, i.e. different equation schemes, is discussed, explaining the strategic design of diffusion couple for a small error range.

Zero-carbon inertization processes of hazardous mine tailings: Mineral physicochemical properties, transformation mechanism, and long-term stability

Hazardous mine tailings (HMTs) dam failures can cause devastation to the ecology environment, people's lives and property, which require expensive and complicated remediation engineering systematacially. A cheap and sustainable inertization disposal is proposed for de-risking HMTs without any carbon emissions, stabilizing hazardous heavy metal cations within safety minerals and also sequestering CO2 in the process, simultaneously. Herein, lead-zinc tailings as target HMTs were inertized by using waste rice husk ashes (RHAs) and carbide slag (CS) with a certain ratio, and lead-zinc tailings hardened pastes (LZTHPs) were investigated based on the experimental performance, analytical characteristics, and simulation diffusion methods, to deeply unveil the minerals transformation mechanisms and long-term stability from the cation perspectives. Results revealed that LZTHPs’ compressive strength ranged from 1.04–4.73 MPa and leaching toxicity concentrations of Pb, Zn, Cr, and Cd reached 0.03 mg/L, 1.78 mg/L, 0.01 mg/L, and 0.01 mg/L, respectively. C-S-H gels (Type I and II), cation hydroxides and CO2 mineralization carbonates were the hydrates in LZTHPs. Pb (86%), Zn (78%), Cr (76%), and Cd (65%) were immobilized as residual state, and CO2 mineralization capacity was 0.16 kg/kg. The diffusion coefficient of Pb, Zn, Cr, and Cd below 4.48 × 10−10 cm2/s, 1.39 × 10−10 cm2/s, 4.72 × 10−10 cm2/s, and 0.30 × 10−12 cm2/s, which would be sufficient in most scenarios to adequately stabilize tailings. Diffusion control is the leaching mechanism of cations. After 100 years of simulation diffusion, the diffusion areas of Pb, Zn, Cr, and Cd are 1.33 × 10−3∼1.49 cm2, 2.47 × 10−4∼0.48 cm2, 2.47–8.61 × 10−4 cm2, and 1.49 cm2, respectively, and the environmental impact of LZTHPs was negligible. This study provides promising solutions for alleviating hazardous tailings dangerous, achieving sustainable development with zero-carbon emission, implying the concept of eliminating waste by waste, synchronously.

Molecular dynamics study on the initial oxidation behavior of FeCr alloys in supercritical H2O and supercritical CO2 with O2

The initial oxidation behavior of Fe10Cr and Fe20Cr alloys in supercritical H2O and supercritical CO2 with O2 at 650 ℃ is investigated by molecular dynamics. O2 has the higher average adsorption energy of −2.54 eV than that of H2O and CO2, indicating that the adsorption state of O2 molecule on FeCr alloys is the most stable. The reactions between O2 and FeCr alloys are the occurs firstly, followed by H2O and CO2. The reaction rates of both FeCr alloys with O2 in supercritical CO2 are higher than that in supercritical H2O. Due to the addition of Cr to FeCr alloys, the outward diffusion coefficients of Cr from FeCr alloys both increase 1.59 × 10−23 cm2/s in supercritical CO2 and H2O with O2.

Preliminary investigation of Cr-coated F82H: Evolution of microstructure and mechanical properties at the F82H/Cr interface during solid-state diffusion bonding above Ac1 temperature

Solid-state diffusion bonding was employed to join F82H steel and pure Cr metal under high vacuum at various temperatures above Ac1 in the range 1114 to 1323 K for 60 min, and at 1323 K for 120 min. After successful bonding at all temperatures, the F82H/Cr interface and interdiffusion zone were characterised using SEM-EDS, TEM and EBSD analysis, with respect to diffusion behaviour, chemical composition and microstructure. A thin interface layer formed on the Cr side of the joint, which decreased in thickness with decreasing bonding temperature, and was rich in M23C6 with mixed columnar and particulate nature. The depth of Cr diffusion into F82H decreased with decreasing bonding temperature. At temperatures ≥1231 K a layer of ferrite grains formed in the F82H region adjacent to the interface, due to the combined stabilising effect of enhanced Cr concentration and depleted C. At the lowest bonding temperature of 1114 K, a lath martensite microstructure was retained throughout the F82H due to a significantly lower extent of Cr and C diffusion. The diffusion coefficient of Cr in F82H was determined at all temperatures examined, and the activation energy of Cr diffusion in F82H >Ac1 was approximated as 225 KJ mol−1. Finally, hardness testing of the interface and interdiffusion zone suggests the F82H properties were retained after bonding at the lowest temperature of 1114 K, however at higher temperatures the newly formed ferrite region was softer. Further research is required to understand the impact of the hard M23C6-rich interface layer on mechanical properties of the joint, and whether microstructural change can be minimised, or even eliminated, below the Ac1 temperature.

Cosmic-ray-driven galactic winds: transport modes of cosmic rays and Alfvén-wave dark regions

ABSTRACTFeedback mediated by cosmic rays (CRs) is an important process in galaxy formation. Because CRs are long-lived and because they are transported along the magnetic field lines independently of any gas flow, they can efficiently distribute their feedback energy within the galaxy. We present an in-depth investigation of (i) how CRs launch galactic winds from a disc that is forming in a $10^{11} \, \rm {M}_\odot$ halo and (ii) the state of CR transport inside the galactic wind. To this end, we use the arepo moving-mesh code and model CR transport with the two-moment description of CR hydrodynamics. This model includes the CR interaction with the gyroresonant Alfvén waves that enable us to self-consistently calculate the CR diffusion coefficient and CR transport speeds based on coarse-grained models for plasma physical effects. This delivers insight into key questions such as whether the effective CR transport is streaming-like or diffusive-like, how the CR diffusion coefficient and transport speed change inside the circumgalactic medium, and to what degree the two-moment approximation is needed to faithfully capture these effects. We find that the CR-diffusion coefficient reaches a steady state in most environments with the notable exception of our newly discovered Alfvén-wave dark regions where the toroidal wind magnetic field is nearly perpendicular to the CR pressure gradient so that CRs are unable to excite the gyroresonant Alfvén waves. However, CR transport itself cannot reach a steady state and is not well described by either the CR streaming paradigm, the CR diffusion paradigm, or a combination of both.

Sintering properties and homogeneity of Ca2+‐doped .65Y2O3–.35YCr0.5Mn0.5O3 NTC ceramics

Sintering properties and homogeneity of Ca²⁺‐doped .65Y₂O₃–.35YCr_0.5Mn_0.5O₃ NTC ceramics

High-temperature corrosion rate and diffusion modelling of Ni-coated incoloy 800H alloy in MgCl2–KCl heat transfer fluid

The polarization and long-term dipping corrosion behaviors of pristine and Ni-coated Incoloy 800H (800H) alloys were investigated in the eutectic MgCl 2 –KCl molten salt at different temperatures and compared their performance with expensive Haynes 230 (H230) alloy. The corrosion rates of all the studied alloys increased with temperature. The corrosion rates obtained from the electrochemical study showed Ni-coating increases the corrosion resistance of 800H alloy. Further, the linear polarization measurements were also performed at different temperatures to investigate the effect of Ni-coating on the exchange-current density. A long-term corrosion study showed that 800H has a higher corrosion rate than H230. However, Ni-coating significantly decreased the corrosion rate of 800H (even lower than H230) in the molten MgCl 2 –KCl salt. A diffusion model for Ni-coated 800H was presented to describe the diffusion behavior of Cr, Fe, and Ni elements in the Ni-coated 800H alloy in a long-term corrosion study. The diffusion model was simulated based on the partial differential equations and known initial boundary conditions. The simulated result is compared with experimental data by altering the diffusion coefficient and reasonable values of diffusion coefficients of Cr, Fe, and Ni in 800H alloy and Ni-coating. The estimated diffusion coefficient (D) values in the Ni-coating from 800H alloy are in the range of 2–4 × 10 −11 cm 2 s ˗1 , 4–6 × 10 −11 cm 2 s ˗1 , and 5–8 × 10 −11 cm 2 s ˗1 for Cr, Fe, and Ni, respectively. The overall results indicated that Ni-coated 800H could be employed as a suitable alternative construction material for solar thermal energy storage containers. • We report polarization and long-term dipping corrosion of pure and Ni-coated Incoloy 800H alloy in MgCl 2 -KCl molten salt. • Measured corrosion rates and weight loss showed Ni-coating on Incoloy 800H substantially increased the corrosion resistance. • Exchange current densities of Incoloy 800H with and without Ni-coating were investigated at different temperatures. • A diffusion model of Fe and Cr elements in Ni-coated 800H alloy was validated experimentally.

Measurements and correlation of infinite dilution binary diffusion coefficients for Cr(acac)3 in high temperature supercritical carbon dioxide

The infinite dilution binary diffusion coefficient (D12) for chromium (III) acetylacetonate (Cr(acac)3) in supercritical carbon dioxide (scCO2) was measured at temperatures from 343 K to 423 K and pressures from 10 MPa to 22 MPa by the chromatographic impulse response (CIR) method. We previously reported D12 data at relatively low temperatures below 343 K; the D12 data were accurately represented by the hydrodynamic equation where the D12/T vs. CO2 viscosity were expressed by a straight line on a logarithmic plot. However, the newly measured D12 values in the present study showed greater deviations at higher temperatures or lower viscosities (lower pressures/densities) from the correlation determined for low – temperature D12 data. The maximum deviation was 68% at the lowest measured CO2 viscosity of 22 μPa s; thus, the hydrodynamic equation could be no longer applied in this region. The D12 data that deviate from the hydrodynamic equation fully correspond to the gas-like scCO2 region, whereas those fitted by the equation correspond to the liquid –like scCO2 region. The gas–like and liquid–like regions can be separated on the basis of density fluctuations and a ridge line in a pressure vs. temperature diagram, claimed by Nishikawa and Morita [Chem. Phys. Lett., 316 (2000) 238]. Compared with the accuracy in predicting the D12 data by the original Schmidt number correlation, the accuracy was improved by the modified Schmidt number correlation, with an average relative deviation of 6.20 % for 136 conditions, including both gas–like and liquid–like scCO2 regions.

Radiation-magnetohydrodynamics simulations of cosmic ray feedback in disc galaxies

ABSTRACT Cosmic rays (CRs) are thought to play an important role in galaxy evolution. We study their effect when coupled to other important sources of feedback, namely supernovae (SNe) and stellar radiation, by including CR anisotropic diffusion and radiative losses but neglecting CR streaming. Using the ramses-rt code, we perform the first radiation-magnetohydrodynamics simulations of isolated disc galaxies with and without CRs. We study galaxies embedded in dark matter haloes of 1010, 1011, and $10^{12}\, \rm M_{\odot }$ with a maximum resolution of $9 \, \rm pc$. We find that CRs reduce the star formation (SF) rate in our two dwarf galaxies by a factor of 2, with decreasing efficiency with increasing galaxy mass. They increase significantly the outflow mass loading factor in all our galaxies and make the outflows colder. We study the impact of the CR diffusion coefficient, exploring values from κ = 1027 to $\rm 3\times 10^{29}\, cm^2\, s^{-1}$. With a lower κ, CRs remain confined for longer on small scales and are consequently efficient in suppressing SF, whereas a higher diffusion coefficient reduces the effect on SF and increases the generation of cold outflows. Finally, we compare CR feedback to a calibrated ’strong’ SN feedback model known to sufficiently regulate SF in high-redshift cosmological simulations. We find that CR feedback is not sufficiently strong to replace this strong SN feedback. As they tend to smooth out the ISM and fill it with denser gas, CRs also lower the escape fraction of Lyman continuum photons from galaxies.

Inter-diffusion and stability studies in W/Cr and W/Fe films using ion beam analysis

Plasma facing components in fusion reactors are exposed to intense plasma and the accompanying thermal loads and undergo surface modification due to sputtering and thermal diffusion. In order to get insight into the thermal diffusion in reduced-activation ferritic/martensitic (RAFM) steel, a prominent W containing plasma facing material, the compositional, structural and morphological changes occurring in W/Cr and W/Fe bi-layered films on vacuum annealing in 373–873 K temperature range were investigated. Compositional analysis by ion beam techniques established the out-diffusion of Cr and Fe through the W layer to the top surface. The diffusion coefficients of Cr and Fe in W were determined to be 8.0 × 10-19 (at 873 K) and 9.75 × 10-18 m2/s (at 773 K) respectively. The out-diffusion of Cr and Fe was substantiated by diffraction studies; however, no inter-metallic phases were formed. Annealing, besides promoting grain growth also introduced roughness in films.

Diffusion of chromium in β-Ti under high pressure

Abstract It is shown that Arrhenius plots of diffusion coefficients of Cr in β-Ti can be represented under each pressure by two straight lines which are fitted in the temperature regions above and below about 1390 K. The activation enthalpies for high temperature are 167 kJ/mol under 0.1 MPa and 191 kJ/mol under 2.1 GPa, and those for low temperature are 147 kJ/mol under 0.1 MPa and 153 kJ/mol under 2.1 GPa. The ratios of activation volumes for impurity diffusion to the molar matrix volume are in the range of 0.38 to 0.45. When the phonon-softening model is applied, the activation enthalpy for the impurity diffusion in the absence of any phonon-induced lattice instabilities is 226 kJ/mol under 0.1 MPa and increases with pressure. Its pressure dependence indicates that the activation volume for the diffusion with no assistance from phonons is 66% of the molar matrix volume, and this result agrees with the activation volume for the diffusion in “normal” bcc metals.

Improving the Corrosion Resistance of AISI 316L Steel for Semiconductor Piping by Controlled Delta-Ferrite Content

This study evaluated changes in delta-ferrite content depending on the preheating of AISI 316L stainless steel. We also determined the reasons for the variation in delta-ferrite content, which affects corrosion resistance. Changes in delta-ferrite content after preheating was confirmed using a Feritscope, and the microstructure was analyzed using optical microscopy (OM). We found that the delta-ferrite microstructure size decreased when preheating time was increased at 1295 oC, and that the delta-ferrite content could be controlled through preheating. Potentiodynamic polarization test were carried out in NaCl (0.5 M) + H2SO4 (0.5 M) solution, and it was found that higher delta-ferrite content resulted in less corrosion potential and passive potential. To determine the cause, an analysis was conducted using energy-dispersive spectroscopy (EDS), which confirmed that higher delta-ferrite content led to weaker corrosion resistance, due to Cr degradation at the delta-ferrite and austenite boundaries. The degradation of Cr on the boundaries between austenite and delta-ferrite can be explained by the difference in the diffusion coefficient of Cr in the ferrite and austenite. A scanning electron microscopy (SEM) analysis of material used for actual semiconductor piping confirmed that corrosion begins at the delta-ferrite and austenite boundaries. These results confirm the need to control delta-ferrite content in AISI 316L stainless steel used for semiconductor piping.

Effect of Heat Treatment Temperature on Microstructure and Properties of PM Borated Stainless Steel Prepared by Hot Isostatic Pressing.

Borated stainless steel (BSS) with a boron content of 1.86% was prepared by a powder metallurgy process incorporating atomization and hot isostatic pressing. After solution quenching at 900–1200 °C, the phase composition of the alloy was studied by quantitative X-ray diffraction phase analysis. The microstructure, fracture morphology, and distributions of boron, chromium, and iron in grains of the alloy were analyzed by field-emission scanning electron microscopy with secondary electron and energy-dispersive spectroscopy. After the coupons were heat treated at different temperatures ranging from 900 to 1200 °C, the strength and plasticity were tested, and the fracture surfaces were analyzed. Undergoing heat treatment at different temperatures, the phases of the alloy were austenite and Fe1.1Cr0.9B0.9 phase. Since the diffusion coefficients of Cr, Fe, and B varied at different temperatures, the distribution of elements in the alloy was not uniform. The alloy with good strength and plasticity can be obtained when the heat treatment temperature of alloy ranged from 1000 to 1150 °C while the tensile strength was about 800 MPa, with the elongation standing about 20%.

Prediction of the diffusion characteristics of the V-Cr system by molecular dynamics based on N-body interatomic potentials

Molecular dynamics (MD) is a promising method for predicting the diffusion characteristics of materials. However, the reliability of MD simulation results is largely determined by the technique of their interpretation and the interatomic potentials used. In this work, interatomic potentials are constructed for calculating the diffusion characteristics in alloys of the V-Cr system. We employed an approach that accurately takes into account the angular dependence of the potential energy of the atomic system. For monoatomic systems V and Cr, we used interatomic potentials that predict thermal expansion and melting point in good agreement with experimental values, along with good reproduction of BCC lattice parameters, sublimation energies, equations of state, elastic constants, and several other properties. The cross potential functions of the V-Cr binary system are optimized with using DFT calculations and experimental formation enthalpy values. The resulting V-Cr potential predicts the dependence of the BCC lattice parameter, the elastic constants of V-Cr solid solutions on the concentration of components and the thermal expansion of the stoichiometric V50Cr50 alloy in good agreement with the known experimental data. The constructed potentials were utilized to calculate the diffusion coefficients in V, Cr, V90Cr10 and V95Cr05 by the molecular dynamics method. We identified that the diffusion coefficient of V exceeds the diffusion coefficient of Cr in solid solutions of Cr in V. The calculated diffusion coefficients are consistent with the known results of diffusion experiments in V, Cr and Cr diffusion in V within the error of measurements. Inclusion of the temperature dependencies of the vacancy formation enthalpy and vacancy formation entropy into calculations of the diffusion coefficient leads to its deviation from the Arrhenius equation and improves the agreement with the experimental data.The good agreement between the independent results of the MD simulation and diffusion experiments confirms both the reliability of the experiment and the MD simulation.

Diffusion of chromium in zinc chalcogenides during hot isostatic pressing

The diffusion of chromium impurities in zinc chalcogenides (ZnS, ZnSe) during hot isostatic pressing (HIP) in the temperature range T = 1000–1330 °C and pressures P = 100–190 MPa has been investigated. The chromium concentration and its distribution over the sample volume with a step from 5 to 50 μm was determined by FTIR spectroscopy in combination with an IR microscope. The diffusion coefficients of Cr in ZnS and ZnSe at various temperatures and pressures were determined. The diffusion coefficients of Cr at 1300 °C were (7.0 ± 0.3) × 10−8 cm2/s in ZnSe and (3.4 ± 0.4) × 10−8 cm2/s in ZnS. It is shown that the temperature dependences are described by the Arrhenius equation, and the isostatic pressure does not affect the value of the diffusion coefficients.

Spectroelectrochemical Behavior of Cr, Fe, Co, and Ni in LiCl-KCl Molten Salt for Decontaminating Radioactive Metallic Wastes

This study examines the thermodynamic, kinetic, and spectroscopic behaviors of Cr, Fe, Co, and Ni to lay the foundation to develop an electrochemical decontamination process for radioactive metallic wastes. Cyclic voltammetry combined with numerical fitting was used to obtain the formal potentials, standard rate constants, and diffusion coefficients of redox reactions, Cr(II)/Cr, Fe(II)/Fe(0), Co(II)/Co(0), and Ni(II)/Ni(0), in LiCl-KCl at 773 K. The order of the diffusion coefficients was 10–5 cm2 s−1, which agrees with the existing data and the standard rate constants showed similar values with the order of 10–3 cm s−1 between experimental correlations and numerical fitting. UV–vis-NIR absorption spectroscopy of the metallic constituents was performed to derive molar absorption coefficients and molecular structures in molten salt media. In particular, the redox reaction of Cr(III)/Cr(II) was investigated by chronoabsorptometry to obtain its formal potential, the number of electrons, and the diffusion coefficient of Cr(II). The obtained reaction properties were used in the numerical modeling of the ECE reaction in a Ni and Co binary system to reproduce the experimental results of CV, revealing the presence of chemical reaction. The findings of this study will be directly used for designing a decontamination process to produce acceptable waste forms and reduce waste volume.

Influence of redox potential on leaching behavior of a solidified chromium contaminated soil

Cement-based solidification/stabilization (S/S) technology is often used to remediate chromium (Cr) contaminated soils. The valence state and mobility of Cr in soils are closely related with redox potential (EH). However, Cr mobilization from the solidified soils influenced by EH has received little attention. In this study, semi-dynamic leaching tests and the toxicity characteristic leaching procedure (TCLP) were performed on a S/S treated Cr contaminated soil under various EH conditions. The effective diffusion coefficient and leachability index were obtained from the leaching data to investigate the leaching behavior of Cr from the S/S treated soil. Speciation of Cr remained in the sample after the leaching process was obtained through the sequential extraction procedures. The results show that an increase in EH increases the effective diffusion coefficient of Cr and, therefore, the amount of Cr leached. This result is attributed to immobile Cr(III) being oxidized to highly mobile Cr(VI). The leachability index results indicate that the cement solidification of Cr contaminated soil may not be appropriate under oxidizing conditions. For the TCLP and sequential extraction procedures, the leached amount of Cr exhibits a strong dependence on EH. As EH increases, the content of Cr remaining in the soil in unstable phases reduced, and more Cr was released to leachant.

First-principles study of chromium diffusion in the ferritic Fe-Cr alloy

Ferritic Fe-Cr alloy is an important interconnect material for solid oxide fuel cell (SOFC) stacking. The Cr2O3 scale growth and Cr-induced cathode poisoning both related to the Cr diffusion have become the main concerns affecting the efficiency and life of the interconnect. In this study, a systematic theoretical study on the point defects and Cr diffusion process in the ferritic Fe-Cr alloy is performed by first-principles calculations. The different crystal models with vacancy or impurity Cr atoms are set up and optimized. The formation energies of two types of Fe vacancy and one type of Cr vacancy are obtained and compared. The adsorption of an impurity Cr atom in the Fe-Cr alloy is investigated and one type of stable tetrahedral interstitial and two types of metastable octahedral interstitials are found. Different diffusion pathways are explored including the vacancy diffusion and the interstitial Cr atom diffusion in the pure Fe layer and in the Fe-Cr mixed layer of the crystal, respectively. It is found that the interstitial Cr atom is easier to diffuse in the pure Fe layer in the studied Fe-Cr alloy. The activation energy and the diffusion coefficient of each diffusion pathway is obtained and the magnitude of Cr diffusion coefficient mainly varies from 10−15 to 10−12 m2/s under the realistic SOFC working temperature of 600 °C-800 °C. Our results provide a profound understanding of the microscopic diffusion mechanism of Cr atom in the ferritic Fe-Cr alloy, which could give theoretical guidance for the inhibition of Cr poisoning in the application of SOFC interconnect.

Dissolution of δ-ferrite and its effect on mechanical properties of P92 steel welds

This paper reports on the dissolution of δ-ferrite in the weld fusion zone using post-weld normalizing and tempering (PWNT) and its effect on mechanical properties. The autogenous gas tungsten arc welding (GTAW) was used to prepare double-sided welded joints of P92 steel. After welding, post-weld heat treatment (PWHT) at 760 °C for 2 h and post-weld normalizing at 1050 °C for 1 h followed by tempering at 760 °C for 2 h were performed. The morphology, composition, structure, and hardness of δ-ferrite are verified. The effect of PWHT and PWNT on mechanical properties is also observed. In as-welded and PWHT conditions, the retention of δ-ferrite was observed while the dissolution of δ-ferrite was confirmed after PWNT. In the PWNT condition, uniform microhardness across the welded joint, increased ductility, and increased Charpy toughness of weld fusion zone (almost equal to as received material) were achieved. Dissolution kinetics of δ-ferrite is quantified using Thermo-Calc for Scheil's solidification calculation and DICTRA for calculating diffusion coefficients of Cr and W at 1050 °C in austenite.