Fe2B Phase Research Articles

Research on the multi environmental corrosion characteristics and mechanism of B4C doped Fe–Cr–Ni composite coating produced by laser cladding

Different Fe–Cr–Ni composite coatings doped with B4C were produced on the surface of Cr12MoV steel by laser cladding. Special attention was paid to the effects of B4C content on the phase composition, microstructure, and corrosion resistance of the cladded layers. The results indicated that the Fe–Cr–Ni composite coating was primarily composed of α-(Fe, Cr) and γ-(Ni–Cr–Fe) solid-solution phases, as well as Fe2B, M7C3, Fe3Si and M23C6 phases. Once the B4C content increased to 10 wt%, the microstructure of the cladding layer became coarse and exhibited the prominent carbide agglomeration. The composite coatings with different B4C contents exhibited superior corrosion resistance compared to the pure substrate in both 3.5 wt% NaCl and 1 mol/L HCl solutions. Furthermore, as the B4C content increased, the corrosion resistance of the coating initially increased and then declined. In particular, the Fe–Cr–Ni composite coating with an 8 wt% B4C content experienced the pronounced passivation in the corrosive media and possessed the optimal corrosion resistance due to the synergistic effect of the passive film and carbide barrier layer.

Adomian decomposition method for modelling the growthof FeB/Fe2B layer in boronizing process

The main objective of this paper is to explore the practical implementation of the Adomian decomposition method (ADM) in effectively solving the system of equations governing boron diffusion during the boronizing process. This study uses ADM to investigate the kinetics of the boronizing process, assess the influence of various parameters on the growth of the layer thickness, and determine the boron concentration in FeB and Fe2B phases. To validate the simulation results, data obtained from the literature were utilized. Overall, this research contributes to understanding the boronizing process and demonstrates the effectiveness of ADM as a mathematical tool for solving complex diffusion equations.

Development of nanocrystallized magnetoelastic sensors with self-biased effect and improved mass sensitivity

The growing demand for cost-effective and wireless sensing technologies requires the development of simple, efficient and optimized sensors able to accurately detecting external agents. Magnetoelastic resonators represent an alternative to the traditional sensing systems, able to combine all the previously cited factors. Several studies have focused on increasing their sensitivity, in order to make it closer to the market. The present study explores thermal treatments as a novel approach to enhance the sensitivity of magnetoelastic resonators, focusing on the positive impact of crystallization processes induced in magnetoelastic platforms. The experimental results confirm an enhancement of resonant frequency and quality factor of the magnetoelastic platforms as treatment temperature increases. Particularly, the sensor annealed at 550 °C shows an increase of the resonant frequency value of 45 % with respect to the as-quenched platform, being that increase of around 1700 % for the quality factor. In addition, the nanocrystallization induction leads to a self-biased resonance, consequence of the intrinsic magnetization resulting from the crystallization in Fe2B and FeCo phases. Further, the study shows the importance of stability in resonant frequency, emphasizing the potential of the 550 °C-annealed platform for mass sensor applications. Gold deposition experiments reveal the enhanced sensitivity of the sensor annealed at 550 °C of 40 % compared to the as-quenched sensor, as well as an increase of 38 % on its accuracy. These findings represent a significant step forward in the development of magnetoelastic-based mass sensors, highlighting the pivotal role of thermal treatments in optimizing sensitivity for practical and efficient external agents detection systems.

Insights on the pulsed-DC powder-pack boriding process: Kinetic, statistic, and electric field dynamics in low and medium temperatures

This study presents novel insights into the Pulsed-DC Powder-pack Boriding (PDCPB) process applied to AISI 1018 steel at low (700 °C) and medium (750–850 °C) temperatures for 1, 2, and 3 h of exposure. The electric field, induced with periodic polarity inversion half-cycles of 10 s under 5–10 A, promoted a constant B+ flux, ensuring a uniform boride layer thickness. The growth of the boride layers was estimated using Dybkov's Chemical Interaction Model (DCIM) and analysis of variance (ANOVA). DCIM established the B activation energies in FeB and Fe2B phases, while ANOVA determined the influence of treatment parameters on the total layer thickness.The results demonstrated a reduction of B activation energies in FeB and Fe2B by up to ∼ 23 % and ∼ 15 %, respectively, compared to conventional powder-pack boriding. These reductions were attributed to electromigration and Joule heating phenomena. ANOVA results indicated that temperature was the most significant parameter (77 %) for total (FeB + Fe2B) layer thickness. At the lowest treatment temperature (700 °C), the highest average boriding media resistance (∼ 3.06 Ω) was measured, and the maximal electric field magnitude (3098 V m−1) was determined through computational analysis.

FeSiBCCr bulk metallic glasses with excellent soft magnetic properties prepared using spark plasma sintering technology

Fe-based amorphous alloys have received much attention in the fields of electronics and electrical due to their excellent soft magnetic properties at high frequency. However, the controllable preparation of large-sized Fe-based bulk metallic glasses (BMGs) still faces numerous challenges. In this study, FeSiBCCr amorphous powders prepared by gas-water combined atomization were used as raw materials, and FeSiBCCr BMGs were prepared through spark plasma sintering (SPS) at different pressures. The microstructure, phase and magnetic properties of the compacts were systematically characterized using SEM, XRD, TEM, DSC, and VSM. The results showed that when the sintering pressure was 50 MPa, the slow densification process dominated by particle rearrangement at the initial densification process made the internal contact resistance of the compacts larger. This led to macroscopic inhomogeneous physical fields and severe local overheating during the later stages of sintering, causing the precipitation of α-(Fe, Si) and Fe3B phases. Although the material exhibited a relatively high saturation magnetization (Bs) of 1.08 ± 0.01 T, the low density and amorphous fraction resulted in a high coercivity (Hc) of 1060.8 ± 37.8 A·m-1. When the sintering pressure was increased to 250 MPa, the degree of particle densification significantly improved, and the temperature inhomogeneity was markedly suppressed due to reduced internal resistance. Thus, the prepared FeSiBCCr BMGs exhibited an extremely high density of 6.66 ± 0.06 g·cm-3 and excellent soft magnetic properties with Bs of 1.23 ± 0.01 T and Hc of 18.8 ± 1.8 A·m-1. This indicated that the FeSiBCCr BMGs prepared in this study exhibited broad application prospects in efficient electromagnetic conversion and advanced electronic devices.

Effect of manganese and vanadium additions on the microstructures and two-body abrasive wear behaviors of Fe–B hardfacing alloys

Fe–B wear-resistant alloys often exhibit brittleness and suboptimal wear resistance, making them unsuitable for severe operational conditions. In this study, we incorporated ferromanganese powder and ferrovanadium powder were compounded into the Fe–B wear-resistant alloy by plasma cladding technology. The results indicate that the addition of a minor percentage of vanadium, such as about 2 wt%, does not induce any changes in the phase composition. The alloy layer primarily consists of (Mn,Fe)2B and γ-Fe, with vanadium predominantly dissolving in the primary (Mn,Fe)2B phase. This dissolution enhances the toughness of the hard phase and refines the grain structure. At around 4 wt% vanadium, a spherical VB phase precipitates. This inclusion elevates the impact toughness of the alloy layer. The impact toughness of the high manganese content with 4.69 wt% vanadium is the highest, up to 39.11 J/cm2, which is about 30 %higher than that of the sample without vanadium. As vanadium content rises, both the hardness and wear resistance of the alloy layer improve. The most optimal performance was observed with a manganese content of 20.15 wt% and vanadium at 4.69 wt%, achieving a hardness of 65.5 HRC and wear amounts of 48.1 mg (24 N load) and 85.0 mg (48 N load).

Influence of boriding on the tribological behavior of AISI D2 tool steel for dry deep drawing of stainless steel and aluminum

Deep drawing of stainless steel and aluminum is a widely adopted method for manufacturing various industrial goods. However, the wear damage produced to die tools is a recurring problem in these processes. While lubricants are often employed to lubricate and reduce die wear, dry deep drawing is the current best alternative for meeting green manufacturing demands. Hence, enhanced solid lubricants or surface treatments for dies are highly required. This study aims to evaluate and compare the tribological behavior of a heat-treated AISI D2 steel and a boriding AISI D2 tool steel against stainless steel (AISI 304) and aluminum alloy (AA 6061 T6) in the absence of lubricant. The boride coating was formed on the AISI D2 steel by the closed-pack boriding technique, resulting in a tooth-saw morphology with an overall thickness of 33.6 μm. X-ray diffraction analysis confirmed the presence of FeB, Fe2B, and Cr2B3 phases on the surface of the borided AISI D2 tool steel. Notably, the boriding treatment led to a significant increase in the surface hardness of the tool steel, reaching a value of 20.7 GPa. The coefficient of friction (CoF) behavior and wear were evaluated by pin-on-disk tests, simulating conditions similar to those found in cold deep drawing operations. The wear surfaces were analyzed by optical profilometry and scanning electron microscopy (SEM). The results suggest boriding as a suitable treatment to reduce wear damage on the surface of deep drawing dies used for stainless steel and aluminum forming processes in the absence of lubricant. Two-body abrasion and adhesion were identified as the main wear mechanisms in AISI D2 steel against stainless steel and aluminum, with a significant amount of oxidation observed when aluminum was tested. Additionally, a reduction of approximately 20 % in the CoF was observed when employing borided tool steel against stainless steel. However, there was an observed increase of around 75 % in the CoF when the borided tool steel was tested against aluminum.

Microstructure Features and Mechanical Properties of Casted CoFeB Alloy Target

CoFeB alloy, as a promising magneto-resistive material, has attracted extensive attention concerning the magnetic properties of its thin film in the field of magneto-resistive random memory (MRAM). Although there are many studies on the magnetic properties of CoFeB thin films, there is relatively little research on the microstructure and mechanical properties of casted CoFeB alloy. In this work, Co20Fe60B20 (at%) alloy was fabricated through the vacuum induction melting method, and its microstructure features and mechanical performance were studied. Scanning electron microscopy (SEM), electron back scatter diffraction (EBSD), and transmission electron microscopy (TEM) were utilized to characterize the microstructure, which consists of the coarse, needle-like Fe2B phase that crystallizes first, the primary lamellar binary eutectic structure (Fe2B + bcc-Fe), and the ternary eutectic structure (Fe3B + Fe2B + bcc-Fe phase). It is found that Fe3B precipitates on the Fe2B with a core–shell structure. The orientation of bcc-Fe is randomly distributed, while there are two main kinds of textures in Fe2B: {100} <001> and Gaussian texture {110} <001>. In terms of mechanical properties, Co20Fe60B20 alloy’s tensile strength is 140MPa, and the yield strength is 87MPa. Because the cracks are easy to generate and expand along the needle-shaped pre-crystallized Fe2B, the plasticity of Co20Fe60B20 alloy is very poor, only 1%.

The Structure of Boride Diffusion Coatings Produced on Selected Grades of Structural Steels

In the article the microstructure and phase composition of boride coatings deposited on selected structural steels were investigated. The boride coatings were produced using pack cementation method using commercial EKABOR-2 mixture containing of 50 wt. % of new and 50 wt. % of used powder. Boride coatings were deposited on alloyed structural steels grades (PN/EN 10084 standard): 16MnCr5, 18CrNiMo7-6, 41CrAlMo7 42CrMo4. Cylindrical samples with a diameter of 30 mm and a height of 30 mm were boronized in powder at 1000°C for 2, 4 and 6 hours in an argon atmosphere. The process was carried out in an industrial CVD Bernex BPX 325S device. The microstructure was analyzed using scanning electron microscope Phenom XL equipped with EDS spectrometer. The XRD phase analysis was conducted using XTRa diffractometer (ARL). The thickness as well as phase composition was analyzed on coatings formed on each grades of steels. The most of obtained boride coatings were characterized by single-phase structure (Fe2B). The formation of brittle FeB phase was detected only on 16MnCr5 steel grades steels.

Melting, Solidification, and Viscosity Properties of Multicomponent Fe-Cu-Nb-Mo-Si-B Alloys with Low Aluminum Addition.

Melting, solidification, and viscosity properties of multicomponent Fe-Cu-Nb-Mo-Si-B alloys with low aluminum addition (up to 0.42 at.% Al) were studied using an oscillating cup viscometer. It is shown that melting and solidification are divided into two stages with a knee point at 1461 K. The temperature dependences of the liquid fraction between the liquidus and solidus temperatures during melting and solidification are calculated. It has been proven that aluminum accelerates the processes of melting and solidification and leads to an increase in liquidus and solidus temperatures. In the liquid state at temperatures above 1700 K in an alloy with a low aluminum content, the activation energy of viscous flow increases. This growth was associated with the liquid-liquid structure transition, caused by the formation of large clusters based on the metastable Fe23B6 phase. Aluminum atoms attract iron and boron atoms and contribute to the formation of clusters based on the Fe2AlB2 phase and metastable phases of a higher order.

Tribological, oxidation and corrosion properties of ceramic coating on AISI H13 steel by rare earth-Cr composite boronizing

In this paper, a rare earth-Cr composite boronizing method to prepare boride ceramic coatings for AISI H13 steel was proposed. The effect of rare earth elements and Cr on the microstructure, hardness, wear resistance, high temperature oxidation resistance, and corrosion of boride ceramic layers was researched. The characteristics of the boride layers were investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM), electron probe microanalysis (EPMA), wear tests, high-temperature oxidation tests, and corrosion immersion tests, etc. The results showed that the boride layer comprised of Fe2B, FeB, CrB and Cr2B phases. The addition of rare earth CeO2 and Cr nanopowder promoted the growth of the boride layer, and its surface hardness increased by 3.5 times compared with that of tempered AISI H13 steel. In addition, the addition of CeO2 and Cr significantly reduced the wear rate of the boride layer, with the surface wear mechanism being abrasive oxidative wear. Furthermore, the oxidation rate of the boride layer was 71 % lower than that of AISI H13 steel, demonstrating excellent high-temperature oxidation resistance; and the boride layer showed good acid corrosion resistance in corrosion immersion tests.

Phase diagram-guided composition design and property investigation of Ni-based filler metals

The fundamental mechanism underlying the formation of brazed joints involves the diffusion of elements between the base metal (BM) and the brazing filler metal (FM). The formation of brittle compounds in FM during the brazing process frequently results in a significant deterioration of the mechanical properties of the brazed joints. Ni and Cu elements exhibit infinite solubility, and the incorporation of Cu element results in a decrease in the liquidus temperature of FM, thereby enhancing its surface wettability on the BM. The present investigation involves the preparation of as-cast and amorphous FMs with varying Cu element concentrations to examine their material properties, such as weldability, wettability, thermophysical behavior, and creep resistance. The thermophysical and mechanical properties of the nickel-based filler metal BNi-2 were evaluated using the JMatPro software for material thermodynamic simulation and compared with data obtained from existing literatures. An analysis is conducted on the creep properties of a novel FM comprising of Ni, Cr, Fe, Si, B, and Cu. The results suggest that the thermophysical properties of BNi-2 filler are minimally impacted by the presence of Cr (6–8 wt%), Fe (2.5–3.5 wt%), Si (4–5 wt%), and B (2.75–3.5 wt%). Furthermore, alterations in the composition of Si and B elements have a significant impact on the distribution of γ and γ′ phases, consequently influencing the creep properties of the material. At 25 °C, the equilibrium phase of BNi-2 with different Cu contents indicates a gradual decrease in the content of γ phase, while the content of γ′ and Cu–Ni phases increases with an increase in Cu content. The BNi-2 filler with 3 % Cu exhibits the most favorable properties in terms of steady creep rate and fracture life compared to other fillers. This is attributed to the competitive equilibrium between the γ phase and Cu–Ni phase. The addition of 6 % Cu element results in the optimal wettability of the filler metal and creep resistance of the brazed joints. It is also observed that as the concentration of Cu reaches 9 %, there is a gradual increase in the FeB phase, a rise in the proportion of brittle compounds, and a decline in the amorphous forming ability.

Pack-boriding of Sleipner steel: microstructure analysis and kinetics modeling

Abstract In this research work, we subjected the Sleipner steel to pack-boronizing within the temperature range of 1173–1323 K, lasting from 1 to 10 h. Our study involved assessing the steel’s microstructure by examining interphase morphology and measuring the layers’ thicknesses through scanning electron microscopy. To determine the phase composition of the boronized layers, we employed X-ray diffraction analysis. Furthermore, we investigated the redistribution of certain elements during the boronizing process using EDS mapping and EDS point analysis. The boride layers were found to consist of FeB and Fe2B phases. We conducted microhardness testing using the Vickers method on the diffusion zone, Fe2B, and FeB. Lastly, we utilized a diffusion model to evaluate the activation energies of boron in FeB and Fe2B, and we presented the results in terms of activation energies.

Improving the Mechanical and Electrochemical Performance of Additively Manufactured 8620 Low Alloy Steel via Boriding

In this study, mechanical and electrochemical performance of borided additively manufactured (AM) and wrought 8620 low alloy steel were investigated and compared to their bare counterparts. The microstructure of borided 8620 exhibited the presence of FeB and Fe2B phases with a saw tooth morphology. Both AM and wrought samples with boride layers showed a similar performance in hardness, wear, potentiodynamic polarization (PD), electrochemical impedance spectroscopy (EIS), and linear polarization resistance (LPR) experiments. However, borided steels exhibited about an 8-fold increase in Vickers hardness and about a 6-fold enhancement in wear resistance compared to bare ones. Electrochemical experiments of borided specimens (both AM and wrought) in 0.1 M Na2S2O3 + 1 M NH4Cl solution revealed a 3–6-fold lower corrosion current density, about a 6-fold higher charge transfer resistance, and about a 6-fold lower double-layer capacitance, demonstrating an improved corrosion resistance compared to their bare counterparts. Post-corrosion surface analysis revealed the presence of thick sulfide and oxide layers on the bare steels, whereas dispersed corrosion particles were observed on the borided samples. The enhanced wear and electrochemical performance of the borided steels were attributed to the hard FeB/Fe2B layers and the reduced amount of adsorbed sulfur on their surface.

Unveiling the pitting corrosion mechanism of borated stainless steel in the wet storage environment of spent nuclear fuels

Borated stainless steels (BSSs) with high neutron absorbability are promising alloys for the wet storage of spent nuclear fuel. However, consensus on the underlying mechanisms for the effects of B content in BSS and H3BO3 in wet storage environment on the pitting corrosion resistance of BSSs is still lacking. To determine the mechanisms, we designed three hypoeutectic BSSs containing 0.6, 1.2 and 1.8 wt.% B and systematically investigated their electrochemical behavior in solutions with various Cl−/H3BO3 ratios through experimental and computational studies. Results revealed that the pitting corrosion resistance of BSS was dependent on the synergistic effect of the pit initiation induced by localized Cr depletion and the pit stable growth caused by microgalvanic effect, causing the pitting corrosion preferentially occurred at the (Cr, Fe)2B/matrix interface. A higher B content increased the density and width while reduced the Cr contents of the Cr-depleted regions, enhancing the susceptibility to pitting initiation. Meanwhile, the strengthened micro-galvanic effect between the (Cr, Fe)2B phase and γ matrix further facilitated the stable pit growth. For the H3BO3 effect, the first-principles calculations indicated that the competitive adsorption of B(OH)4− to Cl− inhibited pitting initiation in solutions with lower Cl−/H3BO3 ratios. However, as the Cl−/H3BO3 increased, the inhibition effect of the H3BO3 was weakened, and the acidizing effect became the dominant factor deteriorating the corrosion property. Ultimately, based on the Cr depletion-microgalvanic synergetic mechanism, the corrosion resistance of the BSS was significantly improved by tailoring the size and distribution of the (Cr, Fe)2B phase.

Alumino-Silico-thermic synthesis of high purity ferroboron alloy and its characterization

High purity ferroboron (Fe–B) alloy is used as an alloying agent for making special grades of steels, Nd-Fe-B magnets etc. In this study, alumino-silico-thermic co-reduction of Fe2O3 and B2O3 was attempted to prepare high purity Fe–B. Extensive differential thermal analysis (DTA) studies were carried out to understand the reduction behaviour of Fe2O3 and B2O3 by Al and Si. DTA exothermic peaks indicated three step reduction of Fe2O3 (Fe2O3→Fe3O4→FeO→Fe) when reacted with Al and Si separately. B2O3–Si system did not show exothermic peaks while heating indicating sluggish or no reduction, however, B2O3–Al DTA peaks indicated two step reduction behaviour. Differential thermal analysis of Fe2O3–B2O3–Al–Si indicated completion of reduction of oxides, and formation of different intermediate phases. Specially designed reduction reactors were used to produce ferroboron alloy in bulk quantities. Thermal analysis results suggested that the formation of aluminium and silicon borides could be avoided using sub-stoichiometric amount of Al and Si, which was further confirmed from the bulk thermit product. Si acted as reducing agent as well as forming low melting slag comprising of Al(Si)–B–O type oxides. Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and Particle Induced Gamma-ray Emission (PIGE) analysis confirmed the presence of 12 wt% boron in the alloy product with lower content (<1 %) of impurity elements like Al and Si. The relationship between the chemical homogeneity with the thermit process parameters was established. Microstructure and mechanical properties confirmed the formation of Fe2B and FeB phase in the thermit alloy.

Relationship among intrinsic magnetic parameters and structure and crucial effect of metastable Fe3B phase in Fe-metalloid amorphous alloys

The intrinsic heterogeneity of an amorphous structure originates from composition, and the structure determines the magnetic properties and crystallization models of amorphous magnets. Based on classical Fe–B binary magnetic amorphous alloys, the relationship between the structure and magnetic properties was extensively studied. The stacking structure of Fe–B binary amorphous alloys exhibit discontinuous changes within the range of 74–87 at.% Fe. The structural feature can be expressed as Amor. Fe3B matrix + Fe atoms are transforming into Amor. Fe matrix + B atoms with the increase of Fe content. The solute atoms are uniformly distributed in the amorphous matrix holes, similar to a single-phase solid solution structure. The transition point corresponds to the eutectic crystallization model composition (Fe82B18 to Fe83B17). A high Fe content will amplify magnetic moment sensitivity to temperature. Under a given service temperature, the disturbance effect of magnetic moment self-spinning will offset the beneficial effect of increasing Fe content and induce the saturation magnetization (Ms) value to decrease. Binary amorphous Fe–B alloys obtain the maximum Curie temperature near 75 at.% Fe, which is slightly smaller than that of the corresponding metastable Fe3B phase, i.e., the amorphous short-range order structure maintains the highest similarity to the Fe3B phase. The chemical short-range ordering (SRO) structure of amorphous alloys exhibits heredity to corresponding (meta)stable crystal phases. The unique spatial orientation structure of the metastable Fe3B phase is the structural origin of the amorphous nature. This study can guide the composition design of Fe-metalloid magnetic amorphous alloys. The design of materials with excellent magnetic properties originates from a deep understanding of precise composition control and temperature disturbance mechanism.

Grain refinement in solidification of undercooled Fe2B intermetallic compound alloy

Spontaneous grain refinement widely occurs in solidification of highly undercooled solid solution alloys, but the case in stoichiometric intermetallic compound alloys is seldom concerned. In this paper, Fe2B alloy was undercooled up to 336 K to investigate the solidification structure’s evolution with undercooling. It is shown that the equilibrium peritectic reaction L + FeB → Fe2B is completely suppressed and there is only an Fe2B phase to solidify at various undercoolings. As the undercooling increases, Fe2B crystals change from a faceted into non-faceted morphology, and grain refinement takes place from 48 K undercooling until a fully refined solidification structure is obtained above 92 K undercooling. When the sample solidified at a large undercooling is immediately annealed at high temperature, the grains are coarsened quickly. In combination with the electron backscattered diffraction and transmission electron microscopy analysis results, it is suggested that the solidification stress-induced recrystallization triggers the grain refinement in Fe2B alloy.

Influence of Nb and Mo Substitution on the Structure and Magnetic Properties of a Rapidly Quenched Fe79.4Co5Cu0.6B15 Alloy.

The importance of amorphous and nanocrystalline Fe-based soft magnetic materials is increasing annually. Thus, characterisation of the chemical compositions, alloying additives, and crystal structures is significant for obtaining the appropriate functional properties. The purpose of this work is to present comparative studies on the influence of Nb (1, 2, 3 at.%) and Mo (1, 2, 3 at.%) in Fe substitution on the thermal stability, crystal structure, and magnetic properties of a rapidly quenched Fe79.4Co5Cu0.6B15 alloy. Additional heat treatments in a vacuum (260-640 °C) were performed for all samples based on the crystallisation kinetics. Substantial improvement in thermal stability was achieved with increasing Nb substitution, while this effect was less noticeable for Mo-containing alloys. The heat treatment optimisation process showed that the least lossy states (with a minimum value of coercivity below 10 A/m and high saturation induction up to 1.7 T) were the intermediate state of the relaxed amorphous state and the nanocomposite state of nanocrystals immersed in the amorphous matrix obtained by annealing in the temperature range of 340-360 °C for 20 min. Only for the alloy with the highest thermal stability (Nb = 3%), the α-Fe(Co) nanograin grows, without the co-participation of the hard magnetic Fe3B, in a relatively wide range of annealing temperatures up to 460 °C, where the second local minimum in coercivity and core power losses exists. For the remaining annealed alloys, due to lower thermal stability than the Nb = 3% alloy, the Fe3B phase starts to crystallise at lower annealing temperatures, making an essential contribution to magneto-crystalline anisotropy, thus the substantial increase in coercivity and induction saturation. The air-annealing process tested on the studied alloys for optimal annealing conditions has potential use for this type of material. Additionally, optimally annealed Mo-containing alloys are less lossy materials than Nb-containing alloys in a frequency range up to 400 kHz and magnetic induction up to 0.8 T.

Fabrication, microstructure, and wear properties of novel Fe–Cr–B–Nb–Mo metamorphic alloy coatings manufactured by the HVOF thermal spray process

Novel Fe–Cr–B based metamorphic alloy coating layers were manufactured using newly designed Fe–Cr–B–C–Mo–Nb metamorphic alloy powders (M1 (Nb:3.50 wt%), M2 (Nb: 1.75 wt%)) and an HVOF (high-velocity oxygen fuel) thermal spray process. The microstructures and wear properties of the coating layers were investigated and compared with those of a conventional Fe–Cr–B based metamorphic alloy (M) coating layer. The investigation of the microstructure revealed that the (Cr, Fe)2B phase is densely distributed in the α-Fe matrix and metallic glass phases in the M and M2 coating layers. The M1 coating layer was mainly composed of the α-Fe phase, some metallic glass, and nano-sized Nb boride particles. The results of measuring the oxide fraction indicated that the M2 layer showed 10 times better in-flight oxidation resistance than the M layers. A wear test resulted in the wear rates of M, M1, and M2 being 1.68 × 10−6 mm3/Nm, 7.65 × 10−6 mm3/Nm, and 8.16 × 10−7 mm3/Nm respectively, indicating that the wear resistance of the M2 coating layer was 2.06 times higher than that of the M coating layer. Based on the above results, the dependence of the wear mechanism of the HVOF Fe–Cr–B based metamorphic alloy coating layers on the additive element content is also discussed.