Effect Of Cr Content Research Articles

Research on the structure-activity relationship of Fe-Cr alloy in marine environment based on synchrotron radiation: Effect of Cr content

A solid-liquid interface will form on the surface of metal materials when immersed in the marine, which determines the corrosion resistance. Alloying is one of the most effective approaches to protect materials from corrosion failure by tuning the structure-activity relationship of the solid-liquid interface. Chromium is the decisive element in determining the corrosion resistance of iron-based alloys because it can increase electrode potential and promote passivation. However, up to date, the effect of chromium on materials service safety has not been adequately validated, which restricted the precise design and application of the corrosion resistance alloys. Herein, we probed the effect of Cr on structure-activity relationship with multiple characterization means including electrochemistry, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), surface enhanced Raman spectroscopy (SERS), synchrotron radiation grazing-incidence X-ray diffraction (GIXRD), and X-ray absorption fine structure (XAFS). The solid-liquid interface is mostly amorphous, with some nanocrystals. The addition of Cr can promote the increase of FeOOH and formation of FeCr2O4, with first increase and then decrease of Cr2O3. The enrichment of FeOOH and Cr2O3 improves corrosion resistance when Cr content is less than 30 wt.%. The formation of FeCr2O4 leads to the transformation from corrosion products to passive film when Cr content exceeds 18 wt.%. In addition, the lack of Cr2O3 and the formation of FeCr2O4 result in the descend of corrosion resistance at 40 wt.% Cr content.

Formation of anisotropic grains and modified ferroelectric properties in Cr‐doped Bi5FeTi3O15 thin films

AbstractAurivillius phase Bi5CrxFe1−xTi3O15 (0≤ x ≤1) thin films are prepared by the chemical solution deposition method, and the effect of Cr content on the microstructure, ferroelectric property, and electric transport behavior of Bi5CrxFe1−xTi3O15 films is investigated. X‐ray diffraction analysis shows that all of Bi5CrxFe1−xTi3O15 films are complete solid solution and maintain the Aurivillius structure. The replacement of Fe3+ with smaller Cr3+ decreases anisotropy and lattice aspect ratio in a‐b plane, which is minimized at the composition of Bi5Cr0.5Fe0.5Ti3O15. This changes the grain shape from sphere to plate, and Bi5Cr0.5Fe0.5Ti3O15 film consists of only plate‐like grains. Cr doping increases saturated polarization (Pm) and decreases coercive field (Ec). Cr doping increases Pm of Bi5CrxFe1−xTi3O15 film to 35 μC/cm2, but decreases Ec down to 125 kV/cm. A decrease in the lattice aspect ratio of a‐b plane promotes the alignment of ferroelectric dipoles under electric field. The frequency‐dependent dielectric property and the leakage current show that the plate‐like grains of Cr‐rich Bi5CrxFe1−xTi3O15 films suppress the transport of carriers from grains to grains and prevents a dramatic leakage current increase. The results of this study provide a design rule to control the ferroelectricity of Aurivillius phase Bi5CrxFe1−xTi3O15 thin films by modifying the composition and lattice aspect ratio.

Effect of Cr content on microstructure, mechanical properties and corrosion behavior of Ti6Al4V alloy produced by selective laser melting

ABSTRACT In this study, the effect of Cr content on microstructure, mechanical properties and corrosion behaviour of Ti6Al4V alloy produced by selective laser melting (SLM) was investigated. The microstructure exhibited that α' martensite and β phase are obtained in SLM processed Ti6Al4V alloy and Ti6Al4V-Cr system alloys. The increment of Cr content results in the increment of β phase amount. The effect of Cr on the compressive strength and plastic deformation of Ti6Al4V alloy was evaluated by a compression test. The results indicate that the Ti6Al4V+5Cr alloy has a higher compressive strength and superior plastic deformation than that of the SLM processed Ti6Al4V alloy under optimum printing parameters. Meanwhile, the Ti6Al4V+8Cr alloy possesses the best plastic deformation and corrosion resistance. The Ti6Al4V-Cr system alloys, due to the combination of good mechanical properties and corrosion resistant, can be potentially applied in automotive, naval architecture and offshore facility manufacturing.

Effects of Cr content on the corrosion behaviour of porous Ni–Cr–Mo–Cu alloys

ABSTRACT The porous Ni-Cr-Mo-Cu alloys were fabricated by an activation reaction sintering technique. The effects of Cr content varied from 10 to 30 wt-% on the corrosion performance of porous alloys in 10 wt-% H2SO4 solution were evaluated using weight-loss method and electrochemical techniques. The structural morphology, phase constitution and elemental distribution were characterized by scanning electron microscopy (SEM), X-Ray diffraction analysis, energy dispersive spectrometer and X-ray photoelectron spectroscopy (XPS). The results indicate that porous Ni-Cr-Mo-Cu alloys possess excellent corrosion performance. With incremental changes in Cr contents, the anticorrosion ability increases as well. Electrochemical measurements illustrate results similar to that of weight-loss method, with the increment of Cr content, the double capacitive loops for the porous alloy increases as well, which illustrate that the corrosion procedure is controllable by electrochemical reaction. Moreover, the charge transfer resistance of Ni30wt-%Cr10wt-%Mo5wt-%Cu is 49.2 times bigger than that of Ni10wt-%Cr10wt-%Mo5wt-%Cu. And the corrosion mechanism was explored by XPS.

Hierarchical NiCr hydroxide nanospheres with tunable domain boundaries for highly efficient urea electro-oxidation

Nickel hydroxide was a promising catalyst for urea oxidation reaction, but its catalytic activity is still far from satisfactory. Structure engineering is an efficient approach to tailoring the electrical conductivity and the quantities of active sites. Herein, a series of hierarchical NiCr hydroxide nanowire-assembled nanospheres with tunable crystallinity have been synthesized by hydrothermal method. The effect of Cr content on the structure and the electrochemical properties of NiCr hydroxides has been investigated. The axially aligned nanowires ensure the exposure of active sites; the crystalline/amorphous domain boundaries are intrinsically more active; the amorphous structure improves the electrical conductivity; the incorporation of Cr3+ promotes the charge transfer kinetics. The 10Cr-Ni(OH)2 with the optimized Cr3+ content and domain boundaries shows the best catalytic performance with a reduction of 35 mV in onset potential relative to the α-Ni(OH)2. In addition, the 10Cr-Ni(OH)2 demonstrates good long-term working stability.

Effect of Cr on microstructures and properties of AlTiVZr0.2Crx light weight high entropy alloys

AlTiVZr0.2Crx (x=0,0.4,1) high entropy alloys have been prepared by powder metallurgy technology, and the effects of Cr content on the microstructures and properties of the alloys have been studied. The results show that the AlTiVZr0.2Crx alloys are mainly composed of body-centered cubic solid solution (BCC), face-centered cubic solid solution (FCC), and Al2Zr, AlTi2 and Cr2Ti intermetallic compounds. The addition of Cr promotes the transformation of the alloys from FCC structure to BCC structure and generate new phase Cr2Ti. The microstructure of the alloys are mainly massive or granulate. The hardness, compressive strength and elastic modulus of AlTiVZr0.2Crx alloys increase with the increase of atomic ratio of Cr content, the maximum hardness of AlTiVZr0.2Cr alloy is 685.3 HV, and the maximum compressive strength and elastic modulus are 1180.36 MPa and 30221.36 MPa respectively. The addition of Cr content also affects the friction coefficient and wear resistance of the alloys. With the addition of Cr, the friction coefficient and wear resistance increase first and then decrease. The wear resistance of the AlTiVZr0.2Cr0.4 alloy is the best in this experiment.

Effect of Cr content on precipitation behavior of (CoCrNi)94Ti3Al3 medium entropy alloys

The L12 nanoparticles-enhanced alloys have huge potential in high temperature applications. In this study, the effects of Cr content on precipitation behaviors of (CoCrNi)94Ti3Al3 medium entropy alloys are investigated. The results indicate the fraction of L12 phase increases with the rising Cr content, meanwhile, the size and coarsening rate of L12 phase decrease, which suppresses the overaged degradation of hardness. The Cr concentration gradient between L12 phase and FCC phase plays an important role in the coarsening process. It is instructive to obtain exceptional nanostructure stability of L12 phase in precipitation-strengthened high entropy alloys via compositional optimization of base elements.

The initial wet oxidation process on Fe-Cr alloy surface: Insights from ReaxFF molecular dynamic simulations

The durable use of stainless steels depends on the formation of a protective chromium-rich oxide layer. To better understand the atomistic mechanism of surface oxide film formed on Fe-Cr alloy, the initial wet oxidation process on Fe-Cr alloy surface was investigated using ReaxFF molecular dynamic simulations. The oxidation process initiates from the adsorption and local dissociation of the water molecules near Cr atoms, followed by the segregation of Cr and the formation of cation vacancies on alloy surface. Meanwhile, the dissociated O and H atoms diffuse into the alloy substrate, which consequently facilitates to form a Cr-rich oxide layer. The compositions of oxide film possess distribution from Cr hydrates and hydroxides, Fe hydroxides and oxides to hydrogen ions with negative charge along depth. It was also demonstrated that there is a charge transfer between the metal atoms and hydrogen atoms. The effects of Cr content (0–20 at.%) and crystal surface orientation on the initial wet oxidation process were further discussed. These results can provide a microstructural understanding of the wet oxidation process on the surface of stainless steels from an atomistic point of view.

Effect of Cr content on microstructure and properties of aged Cu−Cr−P alloys

Abstract The role of Cr in affecting the precipitates and the properties of aged Cu−Cr−P alloys was investigated and discussed. The results show that there are mainly three sizes of Cr phase in aged Cu−Cr−P alloys, among them, the nano-sized Cr phase plays an important role in the strength of Cu−Cr−P alloys. The strengthening effect of Cr phase (less than 5 nm) with FCC structure completely coherent with the matrix is calculated to be about 200 MPa on the basis of dislocation cut-through mechanism. The strengthening effect of Cr phase (10−20 nm) with BCC structure incoherent with the matrix is calculated to be about 100 MPa on the basis of the Orowan dislocation bypass mechanism. The increase of Cr content changes the number and size of nano-sized Cr phase, which causes the mechanical properties of the Cu−Cr−P alloys to increase first and then decrease. The tensile strength of Cu−0.36Cr−0.01P alloy is 572 MPa and its electrical conductivity is 80% IACS after solid solution treatment at 980 °C for 2 h followed by 95% cold rolling and then aging treatment at 450 °C for 1 h.

Effect of Cr content in Ni-based amorphous filler on microstructure and shear strength of K4169 nickel-based alloy brazed joint

Three nickel-based amorphous filler materials with composition of [B-Ni9-xCrx]BSiNi (x = 0,1,2) were designed to braze K4169 superalloy according to cluster-plus-glue-atom model. The microstructure of K4169 nickel- based alloy brazed joints was examined, and the shear strength of the joint was also measured via pressure-shear tests. The brazed seam consists of γ-Ni solid solution, Nb6Ni16Si7 and CrB phases of joint brazed with [B-Ni7Cr2]BSiNi filler. More Nb6Ni16Si7 phase formed in the brazed seam with more Cr addition in filler material, because Cr promoted the diffusion of Nb atoms from base material to brazed seam. Diffusion zone was composed of needle-like Cr-Mo rich borides and blocky MC carbides (NbC, TiC). The amount of Cr-Mo rich borides went up with the enhancement of Cr content in filler material. The shear strength of joint reached 689 MPa when brazed with [B-Ni9]BSiNi filler, followed by 562 MPa with [B-Ni8Cr1]BSiNi filler and 450 MPa with [B-Ni7Cr2]BSiNi filler. In addition, Cr-Mo rich borides and continuous precipitation (Nb6Ni16Si7 and CrB) exhibited low resistance to crack, resulting in the degradation of joint strength.

The effect of Cr content on the corrosion resistance of WC-Ni-Cr-Mo composites

Ni-Cr-Mo is a candidate to substitute Co binders in WC-based composites, where high corrosion resistance is required. This work focused on the effect of Cr on the corrosion susceptibility of WC-Ni-Cr-Mo composites, in acid media. Specimens were produced by powder metallurgy followed by microstructural, chemical and mechanical characterization. Open circuit potential measurements, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were employed to evaluate the corrosion susceptibility of WC-Ni-Cr-Mo alloys with different Cr content. The results highlight the greater aggressiveness of chloride medium compared to sulphate environment, and reveal that Cr can effectively decrease corrosion susceptibility without hampering the mechanical properties in both media, especially in chloride solution, where major improvements are observed.

Reheating cracking susceptibility in the weld heat-affected zone of reduced activation ferritic-martensitic steels and the effect of Cr content

Reduced activation ferritic–martensitic steels with different Cr contents were prepared to investigate the effect of Cr on the reheating cracking susceptibility in the weld heat-affected zone (HAZ). After HAZ simulation, stress-rupture tests were performed at 650–750°C, corresponding to the post-weld heat treatment temperature, using a Gleeble simulator. Increasing the Cr content markedly reduced the rupture ductility, resulting in an increase in the susceptibility to reheating cracking. This was attributed to the intergranular Cr-enriched M23C6 carbides that precipitated along the prior austenite grain boundaries during rupture testing, which acted as crack initiation sites. The size of these carbides increased with increasing Cr content, indicating that an increase in Cr contents easily facilitates formation and growth of microvoids that promote reheating cracking during rupture testing.

Oxidative dehydrogenation of ethane to ethylene in an integrated CO2 capture-utilization process

Integrated carbon capture-utilization provides a viable approach to curb anthropogenic CO2 emissions and, at the same time, produce valuable chemicals and fuels from a waste carbon feedstock. Herein, we report in-situ capture and utilization of CO2 in ethylene production through oxidative dehydrogenation of ethane over adsorbent-catalyst materials consisting of double salt K-Ca and Cr-impregnated H-ZSM-5. The adsorption step was conducted at 600 °C using 10 % CO2/Ar, followed by the reaction step at 700 °C using 5 % C2H6/Ar. An adsorption capacity of 5.2 mmol/g was obtained for K-Ca at 600 °C. The effects of Cr content, C2H6 feed concentration and weight hourly space velocity (WHSV) were investigated to determine the optimum process conditions for this combined process. Under 5000 mL/g h and 5 vol% C2H6 feed concentration, Cr10/HZSM-5 physically-mixed with K-Ca (weight ratio of 1:1) exhibited the highest ethane conversion at 25 % with ethylene selectivity of 88 %, owing to its higher turnover frequency (TOF) number and lower Cr surface density.

Effects of Cr content on compositional evolution and precipitation kinetics of γ′ phase in Ni–Al–Cr alloy: 2D phase-field simulation

The two-dimensional phase-field simulation coupled with the sublattice model is utilized to simulate the γ′ precipitation in Ni-12 Al-x Cr at.% (x = 8, 9, 10) alloys aged at 1073 K for 831 h. The compositional evolution of Cr and Al, and the precipitation kinetics of γ′ phase are studied. At the nucleation and growth stage, the concentration distribution of Cr and Al is characterized by an Al enrichment and Cr depletion at the γ/γ′ interface. As Cr content increases from 8 to 10 at.%, the partition ratio of Al and Ni into γ′ phase is promoted, and the equilibrium volume fraction of γ′ phase is increased, while the Al and Ni atoms at the corner site of L12-Ni3(Al, Cr) sublattice are replaced by Cr atoms partly. Besides, the coarsening rate constants of steady-state coarsening (166.2 < t < 831 h) are less than that of growth and coarsening stage (4.2 < t < 50.0 h), the increased Cr content promotes the coarsening of γ′ phase, and the average radius of γ′ phase obeys the time exponent 1/3 well for a high Cr content alloy.

Effect of chromium-induced (Fe, Cr)3C toughness improvement on the two-body abrasive wear behaviors of white cast iron

An as-cast chromium white cast iron alloy with chromium (Cr) content of 0 wt%, 1 wt%, 2 wt%, 3 wt%, and 4 wt% was prepared via metallurgical smelting and casting processes. The effects of Cr content on the toughness, hardness, and microstructure of (Fe, Cr)3C carbides was evaluated. The results revealed that the microstructure of the as-cast alloys is mainly composed of bulk carbide and the pearlite matrix. The carbide in the alloy without added Cr, i.e., eutectic Fe3C, was characterized by a continuous network structure. With the addition of Cr atoms, the Fe3C-type carbide was transformed into (Fe, Cr)3C, leading to a gradual increase in the fracture toughness of the carbide. This may have resulted from the incorporation of Cr into Fe3C and the consequent crystal-structure transformation of the carbide. When the Cr content of the carbide was lower than the saturation level (<2 wt%), the microhardness of the carbide in the as-cast alloy increased significantly. This resulted from an increase in the number of strong (Fe–Cr) metallic bonds in the carbide. However, for Cr content exceeding 2 wt%, the microhardness increased only slightly. Changes in the mechanical properties of the carbides resulted in improved wear resistance of the materials and changes in the wear mechanism of the carbides. At low Cr content, the wear failure of the carbide was characterized mainly by brittle fracture and peeling. With improvement in the toughening performance, microcutting became the main wear failure mechanism of the carbides and exerted a significant blocking effect on the silicon oxide abrasive.

Effects of Cr Content on Microstructure and Mechanical Properties of WMoNbTiCr High-Entropy Alloys

Refractory high-entropy alloys (HEAs) are promising structure materials in elevated temperature. In the present studies, refractory WMoNbTiCr HEAs with different Cr content were prepared by mechanical alloying followed spark plasma sintering. The effects of chromium content on microstructure and room temperature mechanical properties of WMoNbTiCr HEAs were investigated. The results showed that there are three body-centered cubic (BCC) solid solution phases in the ball-milled powders, including enriching with W, Nb, and Cr solid solution phases, respectively. The bulk WMoNbTiCr alloys were mainly composed of disordered BCC phases and a small amount of Laves phase. As the content of Cr increased from 5 to 20 at.%, the relative content of Laves phase increased correspondingly. With an increase in Cr content, the hardness, fracture toughness, compressive fracture strength, and compressive strain of the WMoNbTiCr HEAs increased, exhibiting the maximum values of 9.73 GPa, 6.68 MPa m1/2, 2116 MPa, and 5.1%, respectively. With an addition of 20 at.% Cr, the WMoNbTiCr HEA exhibited a more refined microstructure. The increasing fracture toughness and compressive strain were mainly attributed to the grain refinement. However, the solid solution strengthening, the second-phase (Laves phase) strengthening, and microstructure refinement resulted in an increase in the hardness and compressive fracture strength.

Effect of Cr content on the passivation behavior of Cr alloy steel in a CO2 aqueous environment containing silty sand

The effect of Cr content in steel on its passivation behavior in a CO2 aqueous environment containing silty sand was investigated. The results indicated that the stability of passive film was improved with increasing Cr content. High Fe3C content accelerated the rapid formation of a passive film as well as precipitates and dislocations. Increasing Cr content enhanced the contents of Cr2O3 and Cr(OH)3 in the passive film. Silty sand increased carrier densities of passive films, thereby reducing their protective effects. The role of the contents of Fe3C and Cr on corrosion mechanism of Cr steel with silty sand was emphasized.

Influence of Cr content on the microstructure and mechanical properties of CrxFeNiCu high entropy alloys

The effect of Cr content on the microstructure and mechanical properties of CrxFeNiCu high entropy alloys (HEAs) was firstly studied by first-principles calculations. The calculated results show that the hardness of the alloys increased with the expense of its plasticity decrease, if the content of Cr in the alloy increased. In order to verify the calculated results, CrxFeNiCu (x = 0.8, 1, 1.5 and 2) high entropy alloys were synthesized by vacuum induction melting in the present study. The results show that as the value of x increased from 0.8 to 2, the crystal structure changed from single phase face centered cubic (FCC) phase to a mixture of FCC and body centered cubic (BCC) phases. For the single phase FCC (x = 0.8) structure, both the tensile strength and hardness values were low, which were 491.6 MPa and 322.2 HV respectively, however, the plasticity was high, reaching 33.2%. With the formation and growth of BCC phase (x = 2) the tensile strength and hardness of the alloy were significantly improved, which were 872.6 MPa and 808 HV, respectively.

Effect of Cr content on microstructure and oxidation resistance of laser-clad Cu-Ni-Fe-Mo-xCr alloy coating

Cu-Ni-Fe-Mo-xCr type alloy coatings with different Cr content were produced on a medium carbon steel substrate by laser cladding in this investigation. The effect of Cr content on macro-quality, microstructure, phase structure and high temperature oxidation resistance of the coatings was revealed by macro photography, optical microscopy (OM), environmental scanning electron microscopy (ESEM) incorporating with EDX microanalysis, X-ray diffraction (XRD) analysis, respectively. Results showed that, the coatings with Cr content ranging from 0 to and 5 wt% are smooth and crack free while the coatings with Cr content ranging from 7.5 to and 10 wt% are smooth but cracked. The volume content of second phase (Fe,Ni,Si,Cr)2Mo and the high temperature oxidation resistance of the coatings are both increased with an increase in Cr content.

Erratum to “Effect of Cr content on interdiffusion and Kirkendall pore formation during homogenization of pack-aluminized Ni and Ni–Cr wires” [Intermetallics 101 (2018) 108–115

Erratum to “Effect of Cr content on interdiffusion and Kirkendall pore formation during homogenization of pack-aluminized Ni and Ni–Cr wires” [Intermetallics 101 (2018) 108–115