Fe Cr Research Articles

Hot-dip aluminizing of Fe–Cr–B cast steel in Al–Ti–B alloy melt

The periodic layered structure (PLS) composed of alternative arrangement of Cr–Al–B MAB phase and FeAl3 was formed at the (Cr, Fe)2B/Al interface during hot-dip aluminizing (HDA) of Fe–Cr–B cast steel in molten Al. However, the effect of alloying element in the Al melt on the PLS was still unknown. This work focused on the effect of Ti on the interfacial reaction between Fe–Cr–B cast steel and molten Al–Ti–B alloy. The Ti atoms in Al–Ti–B alloy melt could partially replace the Cr atoms in the M-sites of the Cr–Al–B MAB phase contained in the PLS after it formed in-situ, leading to the formation of (Cr, Ti)–Al–B MAB phase solid solution. The B atoms in the melt absorbed by the Cr–Al–B MAB phase also accounted for the blackening of the Cr–Al–B MAB phase. It was the first time that the M-site MAB phase solid solution in the Cr–Al–B system was prepared by hot-dip aluminizing.

Study on the microstructure and creep fracture behavior of 22Cr 15Ni steel welded joint after aging at 650 °C

It has been carefully investigated that microstructure and creep fracture behavior of Fe–22Cr–15Ni (SP2215) steel welded joints on aging at 650 °C. The extrapolated stresses for welded joint after aging for 0 h (Aging-0h WJ) and 2012 h (Aging-2012h WJ) at 105 h are 105.2 and 91.7 MPa, respectively. The fracture location for Aging-0h WJ and Aging-2012h WJ was respectively heat affected zone (HAZ) and weld metal (WM). HAZ grain size of Aging-0h WJ was 53–88 μm because of thermal cycling. After 2012h aging, HAZ grain size did not change, but grain boundaries were roughened and M23C6 has been found on grain boundaries. Welding and aging treatment did not cause element migration near the fusion line. However, the decrease in Nb elements on the weld side resulted in a decrease in the amount of NbC, which delayed creep damage. The 2012h aging had no significant effect on the hardness difference between HAZ and WM near fusion line, indicating that the transfer of creep fracture position was caused by microstructure changes. The cluster-like NbC formed in WM of Aging-2012h WJ, which not only reduced Nb solid strengthening effect, but also caused local strain concentration. Moreover, in WM of Aging-2012h WJ, the orientation and hardness differences between large-sized (Nb, Ti) C and matrix, and M23C6 on the grain boundary jointly reduced the WM creep performance.

The Influence of Tempering Parameters on the Microstructure, Mechanical Property, and the Corresponding Strengthening Mechanism of Metastable 301 Austenitic Stainless Steel

Metastable austenitic stainless steels (MASS) are widely used in various industrial applications due to their exceptional mechanical properties. The microstructure of MASS can be regulated through severe plastic deformation, heat treatments, and surface treatments to achieve further improvement of mechanical properties. Herein, nanograin and quasiheterostructure are prepared by cold rolling and annealing process in Fe–17Cr–6Ni MASS. The mechanical response, deformation mechanism, and strengthening contribution of the two steels with representative microstructure are studied. The results indicate that nanograin austenitic steel (803 MPa, 22%) has superior yield strength and similar ductility compared with that of quasiheterostructure steel (600 MPa, 25%). In the nanograin steel, the deformation mechanism is mainly dislocation slip and deformation‐induced martensite transformation, while in quasiheterostructure steel, the deformation twinning is also included for the relative lower stacking fault energy in the coarse grain. The yield strength of nanograin structural steel is about 200 MPa higher than that of quasiheterostructure steel, which can be attributed to the differences in grain refinement strengthening, phase‐transformation strengthening, and precipitation strengthening of Cu particles. The findings presented in this study are informative for modulating MASS properties and ultimately improving the lifespan in a variety of industrial settings.

Medium-Entropy Co–Fe–Cr–Mo Spinel Nanoflowers as Electrocatalysts for Oxygen Evolution

Medium-Entropy Co–Fe–Cr–Mo Spinel Nanoflowers as Electrocatalysts for Oxygen Evolution

Effect of Surface Microstructure on the Corrosion Resistance and Magnetic Properties of an Amorphous Cobalt-Based Co–Si–Fe–Cr–Al Alloy

Effect of Surface Microstructure on the Corrosion Resistance and Magnetic Properties of an Amorphous Cobalt-Based Co–Si–Fe–Cr–Al Alloy

Prediction of phase composition and mechanical properties Fe–Cr–C–B–Ti–Cu hardfacing alloys: Modeling and experimental Validations

Alloys of the Fe–Cr–C–B–Ti alloy system are characterized by brittleness, which can be eliminated by the copper alloy, while corrosion resistance and abrasive wear resistance are significantly reduced. In this article, comprehensive investigations are carried out on the microstructure and mechanical properties of the proposed high-copper boron-containing alloy 110Cr4Cu7Ti1VB. Systematic theoretical and experimental studies encompassed thermodynamic calculations in ThermoCALC, production of flux-cored wires for hardfacing and welding, receipt of SEM images, acquisition of load and unload diagrams (discharge) via instrumental indentation on various phases of the deposited metal, and determination of chemical composition at indentation points through local chemical analysis. Mechanical properties of some phases such as γ–Fe phase (austenite), hemioboride Fe2(В,С) and boron cementite Fe3(В,С) and titanium carbide TiC in Fe–Cr–C–B–Ti–Сг alloy were determined by using density functional theory (DFT) implemented in the CASTEP code. We also compared these compounds; properties with other available commercial compounds, where available. With the knowledge of calculated elastic constants, the moduli, the Pugh's modulus ratio G/B, the Poisson's ratio v and the hardness of the title phases, 110Cr4Cu7Ti1VB were further predicted and discussed.

Development of a duplex stainless steel for dry storage canister with improved chloride-induced stress corrosion cracking resistance

The chloride-induced stress corrosion cracking (CISCC) is one of the major integrity concerns in dry storage canisters made of austenitic stainless steels (ASSs). In this study, an advanced duplex stainless steel (DSS) with a composition of Fe–19Cr–4Ni-2.5Mo-4.5Mn (ADCS) was developed and its performance was compared with that of commercial ASS and DSS alloys. The chemical composition of ADCS was determined to obtain greater pitting and CISCC resistance as well as a proper combination of strength and ductility. Then, the thermomechanical processing (TMP) condition was applied, which resulted in higher strength than ASSs (304L SS and 316L SS) and better ductility than DSSs (2101 LDSS and 2205 DSS). The potentiodynamic polarization and electrochemical impedance spectra (EIS) results represented the better pitting corrosion resistance of ADCS compared to 304L SS and 316L SS by forming a better passive layer. The CISCC tests using four-point loaded specimens showed that cracks were initiated at 24 h for 304L SS and 144 h for 316L SS, while crack was not found until 1008 h for ADCS. Overall, the developed alloy, ADCS, showed better combination of CISCC resistance and mechanical properties as dry storage canister materials than commercial alloys.

Efficient thermodynamic model optimization and uncertainty quantification via integration of combinatorial materials chip and Bayesian approach

Combinatorial materials chips (CMC) are composition spread thin-films deposited on a substrate that can rapidly determine the compositional-temperature information of ternary phase diagrams by high-throughput characterization. In this study, phase boundary information determined by CMC from the recent studies was used as input to optimize the thermodynamic model parameters by ESPEI based on Bayesian approach. The uncertainties in the model were also quantified. Fe–Cr–Ni and Fe–Co–Ni systems were chosen as examples to demonstrate the effectiveness of process. The newly optimized phase diagrams are in good agreement with the experimental results. It is also verified that the model can be effectively optimized by the dense CMC phase boundary data only without including the scattered experimental data. Moreover, the uncertainty in the model is reduced with the addition of CMC data. Finally, probability distributions of various phase combinations in the phase diagram were calculated, providing confidence intervals for material design.

The spatial distribution of potentially toxic elements in the mountain forest topsoils (the Silesian Beskids, southern Poland)

Progressive industrialisation and urbanisation in recent decades have dramatically affected the soil cover and led to significant changes in its properties, which inevitably affect the functioning of other components of the forest ecosystems. The total content of Pb, Cd, Zn, Fe, Cr, Cu, Ni, As, and Hg was studied in twenty-five plots at different heights in the topsoil (organic and humus horizons) formed from the Carpathian flysch in the area of the Silesian Beskids (Western Carpathians). The aim of this article is to analyse the spatial distribution of potentially toxic elements in the mountain forest topsoil in different types of plant communities and to determine the relationship between altitude and potentially toxic elements contamination. The soils studied are acidic or very acidic, with an average range of 3.8 (H2O) and 2.9 (KCl). Concentrations of the metals Cd, Zn, Fe, Cr, Cu, Ni, and Hg on the plots that were analysed are within the range of permissible standards for forest ecosystems in Poland, while Pb and As exceed the permissible standards for this type of ecosystem. Spearman’s rank correlation coefficient showed a high correlation between Fe–Cr (r(32) = 0.879, Pb-Hg r(32) = 0.772, Ni–Cr r(32) = 0.738, Zn-Cd r(32) = 0.734, and Cu-Hg r(32) = 0.743, and a moderate statistically significant positive correlation between Cu-Pb r(32) = 0.667 and As-Pb r(32) = 0.557. No correlation was found between altitude and the occurrence of potentially toxic elements. The geo-accumulation index (Igeo) index, on the other hand, indicates that Pb, As, and Cd have the highest impact on soil contamination in all study plots: it classifies soils from moderately to strongly polluted. The enrichment factor (EF) obtained for As and Hg indicates significant-to-very high enrichment in all areas studied. The potential ecological risk index (PLI) calculated for the sites indicates the existence of pollution in all areas examined. The highest risk categories (considerable to very high) are associated with cadmium and mercury.

The Enhancement Effect of Carbides on the Printability and Mechanical Properties of a Ni–Fe–Cr–Al–Ti Alloy Processed by Electron Beam Freeform Fabrication

The Enhancement Effect of Carbides on the Printability and Mechanical Properties of a Ni–Fe–Cr–Al–Ti Alloy Processed by Electron Beam Freeform Fabrication

Влияние концентрационно-временных условий наводороживающего отжига на насыщение водородом титанового сплава ВТ23

Kinetics of the processes of volumetric and surface unidirectional absorption of hydrogen by two-phase (α+β) — titanium alloy VT23 (Ti—Al—Mo—V—Fe—Cr) at a temperature of 800 °C in the concentration range from 0.2 to 0.8% (wt.) has been studied. It is established that by varying the concentration of introduced hydrogen during volumetric hydrogenation annealing, it is possible to form structures in the volume from three-phase (α+α′′+β) to single-phase β. It is shown that by changing the conditions of hydrogenation and using barrier coatings, it is possible to control the depth of hydrogen penetration and, consequently, the completeness of the α→β transformation, forming a unidirectional gradient structure changing from (α′′+β) at the side of the «entrance» of hydrogen to (α+β) at the opposite one. It is noted that the absorption of 0.6% (wt.) hydrogen during unidirectional surface hydrogenation proceeds 20 times slower than during volumetric hydrogenation. It was established that with unidirectional surface hydrogenation, the hydrogen content in the near-surface layers was 0.2% (wt.) higher than the introduced hydrogen concentration calculated for the sample volume.

Initial oxidation of Fe–Cr alloys at different temperatures and atmospheric conditions: A ReaxFF molecular dynamics approach

Initial oxidation of Fe–Cr alloys at different temperatures and atmospheric conditions: A ReaxFF molecular dynamics approach

Fe–Cr–Al Alloy Development Via Wire-Feed Additive Manufacturing Technology

Fe–Cr–Al Alloy Development Via Wire-Feed Additive Manufacturing Technology

Electrospark deposition of Fe–Cr–Cu coatings on St3 steel

It is well-known that chromium in metallic compositions forms dense passivating films that slow down corrosion. The new Fe–Cr–Cu coating was applied on St3 steel through electrospark deposition in an anode mixture consisting of copper and titanium granules, with the addition of chromium powder ranging from 4.85 to 13.26 wt. %. The weight gain of the cathode increased nearly twofold with the addition of chromium powder to the anode mixture. The structure of the coatings was analyzed through X-ray phase analysis, scanning electron microscopy, and energy dispersive spectrometry. The phase composition of the coatings consists of ferrochrome and copper. It is demonstrated that the proposed method of electrospark processing allows for the creation of Fe–Cr–Cu coatings with an average chromium concentration ranging from 55 to 83 at. %. The average copper content in the prepared coatings varied from 5 to 16 at. %. The highest concentration of chromium was observed in the coating prepared with the addition of 13.26 wt. % Cr to the anodic mixture. The corrosion behavior of the coatings was investigated using potentiodynamic polarization and impedance spectroscopy in a 3.5 % NaCl solution. Polarization tests have shown that applying Fe–Cr–Cu coatings to St3 steel can increase its corrosion potential by 12 to 19 % and reduce the corrosion current by 1.5 to 3.4 times. The microhardness of the coating surface ranged from 3.08 to 4.37 GPa, and the coefficient of friction ranged from 0.75 to 0.91. The maximum hardness and the lowest coefficient of friction were observed in the coating with the highest chromium content. It has been demonstrated that Fe–Cr–Cu coatings can enhance the wear resistance of the surface of St3 steel by 1.5 to 3.8 times.

Structural phase transformation in single-crystal Fe–Cr–Ni alloy during creep deformation using molecular dynamics simulation and regression-based machine learning methodology

Structural phase transformation in single-crystal Fe–Cr–Ni alloy during creep deformation using molecular dynamics simulation and regression-based machine learning methodology

The Cold-Brittleness Regularities of Low-Activation Ferritic-Martensitic Steel EK-181

The behavior of the EK-181 low-activation ferritic-martensitic reactor steel (Fe–12Cr–2W–V–Ta–B) in the states with different levels of strength and plastic properties after traditional heat treatment (THT) and after high-temperature thermomechanical treatment (HTMT) in the temperature range from −196 to 25 °C, including the range of its cold brittleness (ductile–brittle transition temperature, DBTT) is studied. The investigations are carried out using non-destructive acoustic methods (internal friction, elasticity) and transmission and scanning electron microscopy methods. It is found that the curves of temperature dependence of internal friction (the vibration decrement) of EK-181 steel after THT and HTMT are similar to those of its impact strength. Below the ductile–brittle transition temperature, it is characterized by a low level of dislocation internal friction. The temperature dependence curves of the steel elastic modulus increase monotonically with the decreasing temperature. In this case, the value of Young’s modulus is structure-sensitive. A modification of the microstructure of EK-181 steel as a result of HTMT causes its elastic modulus to increase, compared to that after THT, over the entire temperature range under study. The electron microscopic studies of the steel microstructure evolution near the fracture surface of the impact samples (in the region of dynamic crack propagation) in the temperature range from −196 to 100 °C reveal the traces of plastic deformation (increased dislocation density, fragmentation of the martensitic structure) at all of the temperatures under study, including those below the cold brittleness threshold of EK-181 steel.

Atomic Investigation of Corrosion Mechanism and Surface Degradation of Fe–Cr–Ni Alloy in Presence of Water: Advance Reactive Molecular Dynamics Simulation

Atomic Investigation of Corrosion Mechanism and Surface Degradation of Fe–Cr–Ni Alloy in Presence of Water: Advance Reactive Molecular Dynamics Simulation

Development of Fe–Cr–Si deposited layer manufactured by laser directed energy deposition process

In this study, the mechanical and corrosion characteristics of a corrosion-resistant layer made of stainless steel (STS) 316 L and Fe–Cr–Si alloy powder were investigated using laser-directed energy deposition (DED). In the STS 316 L deposited specimen, both the substrate and deposited layer were face-centred cubic (FCC). The deposited Fe–Cr–Si layer was clearly separated from the substrate because it was composed of body-centred cubic (BCC). Despite the phase differences, the surface of the Fe–Cr–Si-deposited layer showed a lower corrosion rate than that of the STS 316 L. All the deposited specimens exhibited typical high-temperature tensile behavior. However, the Fe–Cr–Si deposited layer at 600 °C showed a notable reduction in strength and increased elongation compared to the room temperature (RT) and 300 °C test results owing to the carbide concentration and phase transformation in the deposited layer. Because nuclear facilities mainly operate at temperatures below 600 °C, Fe–Cr–Si materials can also be used as nuclear piping coating materials. This study provides a mechanism for the high-temperature properties and corrosion resistance of the Fe–Cr–Si deposited layer and makes it competitive for application in fourth generation nuclear power systems.

Designing L21-Co2TiAl precipitate-strengthened ferritic alloys with excellent high-temperature mechanical properties

Recently, Fe–Cr–Ni–Al–Ti ferritic alloys strengthened by L21-type Ni2TiAl precipitates have demonstrated superior high-temperature strength compared to conventional ferritic steels. However, it still shows a lower high-temperature strength than that of Ni-based superalloys. Therefore, in the current study, we designed new ferritic alloys to improve the high-temperature strength by introducing L21-Co2TiAl precipitates, known as having better high-temperature properties than the Ni2TiAl structure. Specifically, the Ni element has been replaced with the Co element. In addition, the Ti element has been adjusted because the structural evolutions of precipitates, such as composition, lattice misfit and size rely on the Ti content. For instance, the addition of 2 wt% Ti forms a semi-coherent Co2TiAl precipitate with a relatively low density of misfit dislocations. More Ti addition up to 6 wt % leads to an increase in the lattice parameter of the precipitate, while that of the Fe matrix remains unchanged, which results in an increased lattice misfit. The increased lattice misfit causes a higher amount of misfit dislocations, which leads to a reduction of the elastic strain field around the precipitates. It was found that the semi-coherent interface with a high level of the elastic strain field (2 wt % Ti), as compared to the precipitates with a high amount of misfit dislocations (4 and 6 wt % Ti), plays a crucial role in enhancing the mechanical properties at 973 K. In addition, the designed ferritic alloys show superior strength, compared to the previously-reported ferritic alloys.

Optimization of the Heat Treatment of a Hard Magnetic Fe–30Cr–16Co–1Sm Powder Alloy

Optimization of the Heat Treatment of a Hard Magnetic Fe–30Cr–16Co–1Sm Powder Alloy