Fe Powders Research Articles

Coercivity of Fe–Mn powders prepared through hydrogen reduction of wet-process-synthesized oxide powders

In this study, metallic Fe–Mn soft magnetic powders were produced via hydrogen reduction of the oxide powders consisting of nanoferrites produced by a wet process. The effects of solution concentration and pH value during the wet process on the magnetization and coercivity after the hydrogen reduction were investigated. The experimental results indicated that the solution concentration exhibited no effect on the coercivity, whereas the pH produced a large effect on the coercivity. In the wet process at pH greater than 12, irregular-shaped oxide powders were precipitated. The reduced irregular-shaped metallic Fe–Mn powders showed a small coercivity of approximately 90 A/m. In contrast, at pH = 7–8, both irregular- and plate-shaped oxide powders were precipitated, and the reduced Fe–Mn powders showed a large coercivity of ∼ 250 A/m. The reduced plate-shaped Fe–Mn powders exhibited smaller grain sizes (diameter: 15.9 µm) than those of the irregular-shaped Fe–Mn powders (diameter: ∼120–140 µm), indicating that the plate-shaped Fe–Mn powders exhibited increased coercivities. The plate-shaped metallic powders were produced by the reduction of the plate-shaped oxide powders, which contained ferrihydrite and green rust. These results reveal that the pH value of the wet process changes the oxide shape, which in turn affects the shape and grain size of the metallic Fe–Mn powders. By optimizing the wet process conditions, the coercivity of the Fe–Mn powder was improved to 80.9 A/m, although this value is lower than that of the atomized pure Fe powders.

Effect of Magnesium Addition and High Energy Processing on the Degradation Behavior of Iron Powder in Modified Hanks’ Solution for Bioabsorbable Implant Applications

This paper shows the results of applying a combination of high energy processing and magnesium (Mg) as an alloying element in a strategy for enhancing the degradation rate of iron (Fe) for applications in the field of non-permanent medical implants. For this purpose, Fe powder was milled with 5 wt% of Mg (Fe5Mg) and its microstructure and characterized degradation behavior. As-received Fe powder was also milled in order to distinguish between the effects due to high energy processing from those due to the presence of Mg. The powders were prepared by high energy planetary ball milling for 16 h. The results show that the initial crystallite size diminishes from >150 nm to 16 nm for Fe and 46 nm for Fe5Mg. Static degradation tests of loose powder particles were performed in Hanks’ solution. Visual inspection of the immersed powders and the X-ray diffraction (XRD) phase quantification indicate that Fe5Mg exhibited the highest degradation rate followed by milled Fe and as received Fe, in this order. The analysis of degradation products of Fe5Mg showed that they consist on magnesium ferrite and pyroaurite, which are known to present good biocompatibility and low toxicity. Differences in structural features and degradation behaviors of milled Fe and milled Fe5Mg suggest the effective dissolution of Mg in the Fe lattice. Based on the obtained results, it can be said that Fe5Mg powder would be a suitable candidate for non-permanent medical implants with a higher degradation rate than Fe.

Formation of different phases and their influences on the mechanical and tribological properties of surface alloyed FeCoCrNiAl particles using PTA technique

Titanium alloys (Ti–6Al–4V) are attractive in many industries due to their weight ratio, high thermal stability and corrosion resistance. However, their poor tribological properties limit their usage in many applications. In this work, Fe, Co, Cr, Ni and Al powders are mechanically mixed by ball milling and preplaced on the Ti–6Al–4V substrate. Plasma Transferred Arc (PTA) alloying process is performed to fuse the preplaced powder into the substrate surface. X-ray diffraction (XRD), microstructure and microhardness testing is performed to assess the presence of phases, formation of structure and hardness improvement, respectively. Then, the dry sliding pin-on-disc wear testing is conducted on the substrate and PTA alloyed samples. The various wear mechanism and their corresponding roughness were analysed and discussed. XRD result reveals that the ball milled powder and PTA samples possess BCC and FCC phases. However, BCC phases are formed higher than FCC phases due to rapid cooling and controlled heat input. Moreover, broadened BCC phases are observed in the PTA sample at 27°, 36°, 42°, 54° and 70° than that of the ball milled powder. Microstructure of the PTA sample contains both (Ni, Co) rich inter-dendrite and (Al, Fe, Cr) rich needle like dendrite. The microhardness of PTA region has improved with 2.39 times higher than substrate. The wear resistance of the PTA sample has improved by two times compared to substrate. Abrasive, adhesive and plastic deformation were observed on the worn out substrate while PTA sample showed with mild abrasive wear with reduced roughness. The overall results reveal that the various elements are properly alloyed on the Ti–6Al–4V surface through the PTA process and significantly improved the wear resistance. As a result, the PTA process can be used for alloying of other elements to improve the wear resistance of Ti–6Al–4V substrate.

Influence of porosity to dynamic Young’s modulus of sintered iron. Bayesian approach

In this paper Young’s modulus against porosity relation E/Eo = f(P) for sintered Fe and steel powder compacts is discussed. For the experiment beam like (5 × 10 × 50 mm3) compacts, in density range 6.6–7.0 g/cm3 (P = 0.12–0.09), prepared from Fe powder (ASC100.29) are sintered in industrial conditions. Elastic constants E, G, ν are calculated from experimentally obtained fundamental mode shape frequencies, specimen mass and dimensions, using impulse excitation technique (IET). To ensure free beam boundary conditions, supports are placed in mode shapes nodal points. Popular model equation is fitted to experimental data. A Bayesian approach is used for parameter estimation. Fitted model equation predicts reasonably well the data from our and another researchers experiments with pre-alloyed Fe-Cr-Mo powder compacts, but fails for sintered steels prepared from powder mixtures and diffusion alloyed powders with Cu additions.

Fabrication and characterization of iron (Fe) nanoparticles by Hall-Williamson, ball milling and X-ray diffraction method

Iron (Fe) powder was ball milled in an argon inert atmosphere. The milled powders were characterized by X-ray diffraction. The high-energy ball milling of Fe after 20 h resulted in particle size of 38.44 nm. Lattice strains in Fe powder produced by milling have been analyzed by X-ray powder diffraction. The lattice strain (ε) and Debye-Waller factor (B) are determined from the half-widths and integrated intensities of the Bragg reflections. Debye-Waller factor is found to increase with the lattice strain. From the correlation between the strain and effective Debye-Waller factors have been estimated for iron. The variation of energy of vacancy formation as a function of lattice strain has been studied. In the present study, the Hall-Williamson (HW) and Ball Milling (BM) method was used. Mechanical properties, i.e., Lattice Strain (LS) and Particle Size(PS) of Fe nanopowders have been systematically studied. SEM values of particle size 175 nm for zero hour and 45 nm for 20 h. The SEM values agree well with estimated values 168.46 nm for zero and 38.4 nm for 20 h by Hall-Williumson method.

Study on the Doping Effect Cr-doped Fe Metal Powder and Sintering Temperature on Microstructure and Mechanical Properties of Spur Gear Fabricated by Powder Metallurgy

We fabricated mechanical parts of the automotive machines by using Cr-doped the Fe metal powder. We used water as a binder and used a mechanical press for compaction of about 20 ton/in2 followed by non-reactive sintering at 1100 oC. Cr doped Fe metal powder was prepared in the form of GC with percentage values of 0, 0.5, 1.0, 1.5, and 2.0%. The Cr element has been successfully distributed into the main ferrite or Fe phase. However, there is a difference when the Cr percentage is 2%, it is possible that saturation will occur which results in the accumulation of Cr powder so that a new phase is formed which gives rise to new granules. We can confirm that there is a certain limit in the addition of the element Cr in the manufacture of gears made from Fe powder. Based on the calculation, the average number of the Vickers microhardness as a function of Cr content of 0, 0.5, 1, 1.5, and 2% respectively were estimated at about 131, 184, 291, 302, and 270 HV/0.01, respectively. Furthermore, four samples with different sintering temperatures were prepared for comparative purposes. The shrinkage ratio of the GC after sintering at 900, 1000, 1100, and 1200 oC was estimated to be 4.3, 5.7, 7.6, and 9.4%, respectively. The shrinkage ratio of the GC increased linearly when the sintering temperature increased. Sintering temperature variations produce differences in the microstructure of each sample. With the increase of the sintering temperatures, the grains will reach a permanent bond because the constituent particles are fully agglomerate. As a result, grain boundaries between particles will decrease causing the dimensions of the product to shrink so that its density increases. Theoretically, the density value is inversely proportional to porosity. The higher the density value of a product, the lower the porosity value. Increasing the sintering temperature could lead to the appearance of a liquid and the healing of pores. The hardness value and the shrinkage ratio increased with the sintering temperature increased from 900 to 1200 oC. The hardness value increased from 297 to 305 HV/0.01, as the sintering temperature increased from 900 to 1200 oC.

Исследование применения композиционного материала для временного ремонта запорной арматуры на магистральных нефтепроводах

The paper presents the results of studies of composite materials based on epoxy resins with different types of filling are considered. It is shown that a material with a metal filler has higher mechanical characteristics compared to a material filled with ceramics. The material retains high mechanical properties at low temperatures and after interaction with petroleum products. Hydraulic tests showed that the material with a ceramic filler withstood only on non-through defects. The metal-filled material has passed the tests for non-through defects and through defects at pressures up to 4,0 MPa. The material with a filler based on Fe and Cr powder can be used in pipeline construction for temporary repair of valves with non-through defects or through defects of valves operating up to 1,6 MPa.

Effect of Process Control Agents on Fe-15at.%Nb powder during Mechanical Alloying

In this paper, Fe-15at.%Nb alloys were produced from high purity Fe (min. 99.8%) and Nb (min. 99.8%) powders via a mechanical alloying process. The effects of different Process Control Agents (i.e., methanol, hexane, and stearic acid) were investigated with powder morphologies, particle size distribution, and phase formation, and were sampled after up to 80 milling hours at 350 rpm. The powder morphologies and particle sizes were evaluated using scanning electron microscopy and laser diffraction analysis, respectively, and phases were identified via X-ray powder diffractometry. The results demonstrate for all conditions that, in the early stages, there was significant particle agglomeration due to the ductile-ductile feature of Fe and Nb powders, and latter an amorphization trend up to 80 milling hours. Methanol was the most efficient Process Control Agent in terms of avoiding cold welding, reducing of agglomeration, particle size distribution, reducing contamination and crystallinity reduction rate.

Investigation on aluminum based surface composite through FSP using metal (Fe-Sn-Mn) and ceramic (SiC) reinforcements

In the present study, the surface composite was fabricated via friction stir processing on AA5083 using mixture of Fe powder, SiC, Sn and Mn powder. Microstructural characterization with the help of bead geometry and micro-hardness analysis were performed to study the various zones of the processed samples. L4 orthogonal array from the Taguchi method is used for analysis. Improvement in microstructure and hardness is achieved at a rotational speed of 900 rpm, traverse speed of 50 mm/min and 24 mm shoulder diameter. Grain size is varying from one zone to another and enhanced properties are obtained because of grain refinement after friction stir processing.

Structure and properties of powder alloys Fe–(45-15)%Ni–(10-5)%Cu, obtained via mechanical alloying

The article investigates the structure and properties of Fe–(45-15)%Ni–(10-5)%Cu powder alloys. The production method included low- and high-energy (mechanical alloying, МА) treatment of Fe, Ni, and Cu powders in a planetary ball mills followed by hot-pressing of mixes at 950 °С. After MA, the mixtures consist of composite granules with a lamellar structure and particle size of 10–100 μm. After low-energy treatment, three phases were detected by XRD in hot-pressed samples: α-Fe-based solid solution BCC-(Fe, Ni, Cu), Ni-based solid solution FCC-(Ni, Fe, Cu), and FCC-FeO. The appearance of FeO is caused by the partial oxidation of iron during mixing and hot pressing. The total oxide content does not exceed 1.3 wt%. For Fe-X% Ni-5% Cu alloys the ultimate bending strength depends on the nickel content (X, %) linearly according to the equation σben = −19⋅X + 1995 [MPa], where 15 % ≤ X ≤45 %. Alloys obtained by MA have a homogeneous structure and depending on the composition can be either two- or three-phase. As a result of MA the hardness of the alloys increased by 20–21 HRB, and the ultimate bending strength increases by 300–540 MPa. The alloy with the composition 80%Fe-15%Ni-5%Cu has the maximum bending strength σben = 2135 ± 60 MPa. The wear of MA alloys is (4.1–4.4)⋅10−5 mm3 /(N⋅m) which is more than two times lower than the wear of alloys obtained by low-energy treatment. This work was carried out with financial support from the Russian Science Foundation (Project No. 17-79-20384).

Mechanical properties of ultra-high strength cement-based materials (UHSC) incorporating metal powders and steel fibers

In this work, the mechanical properties of ultra-high strength cement-based materials (UHSC) incorporating metal powders and steel fibers under steam curing and autoclave curing were studied, with the special attention devoted to the flexural load-deflection response and compressive stress-strain behavior. Additionally, the hydration degree, pore structure characteristics and micro interface morphology were investigated to provide a thorough insight into the enhancement mechanism of metal powders and steel fibers on UHSC. The results show that the incorporation of Fe and Cu powders could enhance the flexural performance of UHSC, including the increased flexural strength and energy absorption capacity. Under uniaxial compression, improved peak stress, secant modulus, and energy absorption capacity of UHSC could be observed after the addition of Fe powders, but this improvement was negligible after the addition of Cu powders. Moreover, the statistical damage constitutive model based on strain equivalence hypothesis and improved statistical damage theory could reasonably describe the stress-strain behavior of UHSC under uniaxial compression. Furthermore, incorporating Fe and Cu powders could ameliorate the pore structure of UHSC, in which the harmful pores was converted into less harmful pores. Micro-interface morphology demonstrated that metal powders were closely bonded with cement paste, and no cracks or micro pores could be detected around the interface.

Microstructure and mechanical properties of novel tungsten heavy alloys prepared using FeNiCoCrCu HEA as binder

In the present work, novel tungsten heavy alloys (WHAs) have been developed using FeNiCoCrCu high entropy alloy (HEA) as binder through conventional sintering process. The composition of the alloy is 90 wt% W-10 wt% HEA. FeNiCoCrCu HEA was prepared by mechanical milling of elemental Fe, Ni, Co, Cr, and Cu powders in an equiatomic ratio for 60 h. XRD analyses revealed that HEA contains predominant FCC phase along with BCC minor phase. In order to evaluate the effectiveness of FeNiCoCrCu HEA as a binder of WHA, in this study, W and HEA were mixed in the ratio of 9:1, pressed and sintered at temperatures of 1470 and 1500 °C for dwell time of 1 h 30 min under hydrogen atmosphere. These sintered samples are mentioned as WHEAs (W-High Entropy Alloys). The evolution of phases, microstructures, and mechanical properties was investigated as a function of sintering temperature vis-á-vis those prepared by mixing of W and Fe, Ni, Co, Cr, Cu in the same proportion as in HEA (W-EleMental: WEM). The effect of hydrogen treatment (HyT) prior to the sintering of WHEAs on above mentioned characteristics was studied. Structural investigation of WEMs and WHEAs showed high intense W-peaks. Micrographs of these sintered samples showed typical liquid phase sintered microstructures having three distinct phases: bright W-phase, gray matrix phase, and black Cr-oxide phase. With the increase of sintering temperature and introduction of HyT step, the volume fraction of solid W-grain has been increased and W-content in the matrix of WHEAs is reduced. Upon sintering, WHEAs yield better densification, higher compressive strength, and higher bulk hardness. This increase of strength from WEMs to WHEAs was attributed to better densification of WHEAs compared to the former. The maximum values of compressive strength (1912 ± 14 MPa) and bulk hardness (479 ± 16 VHN) were achieved in the case of hydrogen treated W-HEA powder sintered at 1500 °C.

Using the thermochemical corrosion method to prepare porous diamonds

To improve the grinding precision and efficiency of diamond abrasives in slurries, a new type of porous diamonds was prepared by the thermochemical corrosion method. Fe, Fe2O3 and Fe/Fe2O3 were separately used as corrosive agent to explore formation mechanism of porous diamond. The results showed that Fe began to graphitize diamond at 800 °C, whereas Fe2O3 began to oxidize diamond at 700 °C. Neither was able to individually corrode the diamonds into a porous structure. Impressively, it was when a mixture of Fe and Fe2O3 powders was used as the corrosive agent that the diamonds were able to take on a porous structure. Compared to ordinary diamonds, the porous diamonds produced in our study had outstanding advantages of high specific surface area and larger pore volume, which resulted in the porous diamonds having remarkable self-sharpening properties. Grinding contrast experiments were conducted on sapphire substrates using ordinary diamonds slurry and porous diamonds slurry. Notably, when porous diamonds were used as a grinding agent in the slurry, the sapphire substrate removal rate remarkably increased by 26%, and the surface roughness (Ra) of the sapphire substrate significantly decreased by 31%. In this paper, a simple and robust method was proposed to fabricate diamonds with a novel structure, which may help to reduce the surface grinding damage inflicted on hard and brittle materials and improve the quality of processed surfaces and grinding efficiency.

Utilizing aluminum sheets with FeCu deposits as cheap water cleaning electrodes

This work investigates the synthesis of Fe-Cu bimetallic alloy and its subsequent deposition on aluminum substrates for iron contaminants elemination in aqueous solutions. The sequential processes of synthesis (with grinding balls) and deposition (without balls) are carried out in a single ball mill resulting in a coating at room temperature. Detailed microstructural analysis revealed the successful deposition and a single-phase uniform coating of up to 500 nm layer thickness. Magnetic and electrical transport properties of the coating were studied. The coated aluminum electrodes, magnetized via an electromagnet, were eventually used in an aqueous solution containing Fe powder. The transmission of the solution was studied before and after the insertion of the electrodes and the tests revealed a significant increase in transmission from only 20% to around 40%. This is a promising result of an electrode that would normally behave as a paramagnet while being both cheap and recyclable.

Investigations on mechanical properties of secondary recycled ABS reinforced with Fe powder for 3D printing applications

Researchers throughout the world extensively adopting recycling techniques in order to manage polymer waste. But hitherto, less work has been performed on fabrication of fused filaments based on secondary (2°) recycled acrylonitrile butadiene styrene (ABS) polymer reinforced with industrial waste of Fe powder. In present study, efforts have been made on development of composite filaments for fused deposition modelling (FDM) technique of additive manufacturing by controlling different parameters like speed, temperature and load of twin-screw extruder using recycled ABS reinforced with Fe powder. Total nine composite filaments were prepared by taking 90% ABS and 10% Fe powder by weight. The maximum peak strength (32.82 MPa) of ABS + Fe based composite filament was observed at 15 kg (load), 225 °C (extrusion temperature) and 70 rpm (speed) whereas the maximum %BE (7.13%) was obtained at parametric settings of 10 kg, 245 °C and 70 rpm respectively. The observed mechanical and thermal properties of the composite filaments were analysed through porosity analysis, scanning electron microscopy characterization and differential scanning calorimeter.

Terahertz linear polarizers fabricated using magnetorheological fluid

In this work, we fabricated a metacomposite using magnetorheological fluid, in which Fe nanoparticles dispersed in silica gel spontaneously aligned under a magnetic field to form chain-like grids, thus working as a wire-grid polarizer. A single-layer polarizer was fabricated by mixing silica gel, silicone oil, high-purity spherical Fe powder with about 100 nm in diameter, followed by spin-coating and curing the mixture under a uniform magnetic field to form a solid matecomposite layer on a Teflon substrate. The polarizer was characterized by terahertz time-domain spectroscopy, showing good anisotropy and polarizing characteristics. Its performance was improved by multiple-layer stacking. The extinction ratio and degree of polarization of a five-layer polarizer are above 20 dB and 0.95 respectively in a frequency range of 0.8–2 THz.

Effects of Al and Fe powders on the formation of foamed cement obtained by phosphoric acid activation of volcanic ash

The present study aims to compare the effects of aluminum (Al) and iron (Fe) powders as a foaming agent in the synthesis of cement based on phosphoric acid activation of volcanic ash. The compressive strength, X-ray diffraction and microstructure were performed on specimens to elucidate the mechanism involved. The results obtained has proven that the reduction of compressive strength and mass are more prominent with the addition of Al than that of Fe. Also, the addition of Al and Fe induced respectively the formation of amorphous AlPO4 and FeHPO4. Thus, the formation of foams cements can be controlled by the addition of appropriate foaming agent.

Achieving in-situ alloy-hardening core-shell structured carbonyl iron powders for magnetic abrasive finishing

The finishing accuracy and efficiency of magnetic abrasive finishing (MAF) are mainly depending on magnetic abrasive powders (MAPs). A new kind of core–shell structured carbonyl iron powders (CI-MAPs) with a hard Fe/Al intermetallic shell for magnetic abrasive finishing is successfully synthesized by in-situ alloy-hardening the surface of spherical carbonyl iron powders in this study. The feasibility of such an in-situ alloy-hardening strategy is theoretically designed according to the Fe/Al intermetallic compound formation chemical reaction using the Gibbs free energy principle and the TG-DSC testing, and thus the experimental thermodynamics temperature and time ranges of such chemical reactions are proposed. Experimental results shown that a densely zigzag-like uniform alloy-hardening layer with a thickness of about 11 μm, which are composed of Fe3Al, FeAl, and Fe2Al5 intermetallic compounds, was in-situ chemically synthesized on the surface of the spherical carbonyl Fe powders. The achieved core–shell structured powder is performed to finishing a Zirconium tube experimentally, and the roughness (Ra) of the Zirconium tube is greatly improved from 0.361 μm to 0.085 μm by 3 MAF passes.

Application of Al2O3/iron-based composite abrasives on MAF process for inner surface finishing of oval-shaped tube: predicting results of MAF process using artificial neural network model

The oval-shaped tubes are the valuable product for using to transport the clean gas and high-purity solutions in the field of aerospace, semiconductor, LCD, and medical industries. However, due to their complex shape, it could significantly difficult to improve their inner surface quality by the conventional processes. In this study, the application of Al2O3/iron-based composite abrasives on magnetic abrasive finishing (MAF) process was used to finish the inner surface of oval-shaped SUS 316L tubes. Their inner surface was finished by a mixture of magnetic abrasive tools of Al2O3/iron-based composite abrasives with Fe powders, and light oil. An artificial neural network (ANN) model was used to predict the results of MAF process and then was compared with the actual test. It is found that the results predicted by the ANN model have significant agreement with the actual test results. The correlation coefficient (R2) for both training and testing of surface roughness on span and rise portion is larger than 0.92, and RMSE values for both cases are extremely small (less than 0.01). The actual test results showed that the inner surface of oval-shaped SUS 316L tube was smoothly improved from 0.24 μm to 0.05 μm and 0.04 μm on the rise and span portion, respectively. The application of Al2O3/iron-based composite abrasives on MAF process is an efficient method for inner surface finishing of the oval-shaped tubes.

Galvanic corrosion induced by heterogeneous bimodal grain structures in Fe-Mn implant

Fe is a promising implant material but its application is obstructed by the slow degradation rate. The introduction of Mn in Fe offers potential because the Fe-Mn alloy has improved degradation rate and antiferromagnetic behaviour. Nevertheless, the problem of slow degradation rate persists in that alloy. In this study, a heterogeneous bimodal micro/nano-structured Fe-Mn alloy was prepared by mechanical alloying (MA) and laser powder bed fusion (LPBF). In detail, the Fe and Mn powders were mechanically milled, of which the impact energy exerted plastic deformation not only refined the grains to nanometres, but also promoted the solid solution of Mn (austenite forming elements) in Fe, and thus obtaining the nano γ-austenite grains. And then the nano-structured powders were blended with unmilled Fe-Mn powders which had micro-structured grains to prepare the bimodal-structured powders. Subsequently, the bimodal powders were prepared by LPBF, in which the fast cooling rate maintained the heterogeneous bimodal grain structure. Results showed that the prepared bimodal alloy had a mixture of micro α-ferrite grains and nano γ-austenite grains. The active γ-austenite grains were predominately anodic while the negative α-ferrite grains act as cathodes, between them a galvanic current flow generated to accelerate degradation. More significantly, the mixture of micro- and nano-sized grains enlarged the electrochemical heterogeneity characteristics of the alloy, which not only encouraged the corrosion susceptibility but also increased the destabilization of the passive film, and thus further promoting the degradation propagation. The electrochemical experiments showed that the bimodal alloy corroded at a higher current density of about 50.2 μA/cm2 compared with the micro (11 μA/cm2) and nano (18 μA/cm2) groups. In summary, the heterogeneous bimodal Fe-Mn alloy could be a reliable alternative for repairing bone defects.