Fe2B Layers Research Articles

Growth kinetics of Fe2B layer formed on the surface of borided AISI M2 high-speed steel

Abstract In this study, the growth kinetics of the Fe2B layer was investigated and formed on the surface of borided AISI M2 high-speed steel. Boriding treatments carried out by the pack-boriding method were carried out using Ekabor 2 boriding agent at 1,173, 1,273, and 1,373 K for 2, 4, and 6 h. After the boriding processes, the samples were prepared metallographically and their microstructures were examined with the help of backscattered electrons (BE) by scanning electron microscope (SEM). Following SEM examinations, microhardness measurements were carried out from a single sample using 100 g with the Vickers indentation method to understand whether the layer hardness was compatible with Fe2B. When the results of the experimental studies are compared with the results of the literature, it has been determined that AISI M2 high-speed steel can be borided and the boride layer formed on the surface is single-phased (Fe2B), unlike that formed on many other steel types. After determining that the layer formed on the borided AISI M2 surface is single-phase Fe2B, the growth kinetics calculations of this phase were carried out with the help of the Arrhenius equation.

Microstructural and kinetics analysis of FeB–Fe2B layer grown by pulsed-DC powder-pack boriding on AISI 316 L steel

In this study, novel findings were obtained regarding the influence of a 10 A current intensity on the growth of an FeB–Fe2B layer during pulsed-DC powder-pack boriding. Boride layer formation was carried out on AISI 316 L steel at 1123–1223 K for different exposure times at each temperature, considering 10 s polarity inversion cycles. The boride layer was characterized by x-ray diffraction and high-speed Berkovich nanoindentation, the latter being used to determine the hardness and reduced Young’s modulus mappings along the depth of the layer-substrate system. Moreover, the growth kinetics of the FeB–Fe2B layer on the steel’s surface was modeled using the heat balance integral method (HBIM). This involved transforming Fick’s second law into ordinary differential equations over time, assuming a quadratic boron concentration profile in space to determine the B diffusion coefficients in FeB and Fe2B, respectively. From the Arrhenius relationship, the B activation energies in the boride layer were estimated considering the contribution of the electromigration effect; the results showed an approximately 30% reduction compared to the values obtained in the conventional powder-pack boriding for AISI 316 L steel. Finally, the theoretical layer thickness obtained by the HBIM demonstrated an error of no more than 5% against the experimental FeB and FeB + Fe2B layer thickness values.

Boriding Effect on the Hardness of AISI 1020, AISI 1060, AISI 4140 Steels and Application of Artificial Neural Network for Prediction of Borided Layer

Artificial neural network approach was used to predict the thicknesses of total (FeB+Fe2B), FeB and Fe2B borides layers of AISI 1020, AISI 1060, and AISI 4140 steels. Boronizing heat treatment was conducted in a solid medium comprising of EKabor®2 powders at 840–960 ˚C at 40 ˚C intervals for 2, 4, 6, and 8 hours. Optical microscope analysis of the borided layer revealed the saw-tooth (columnar) and planar morphology. The depth of the total (FeB+Fe2B), FeB and Fe2B boride layers was accurately predicted. For total boride layers generated by the artificial neural network model, the average error varied between 0.04 and 7.64 µm. Micro hardness values increased by 423% in AISI 1020, 336% in AISI 1060, and 411% in AISI 41040 after the boronizing process.

The Effect of Chemical Composition on the Microstructure and Properties of Multicomponent Nickel-Based Boride Layers Produced on C45 Steel by the Hybrid Method

Layers of iron–nickel Fe-Ni-B-type borides were produced on C45 steel using a new hybrid treatment variant which combines boriding under glow discharge conditions with galvanic nickel precoating. The aim was to investigate whether these layers could constitute an alternative to the previously developed multicomponent Fe-Ni-B-P-type layers produced by a hybrid treatment variant using chemical nickel precoating. The basis for assessing the effects of both alternative treatments was a comparative analysis of the microstructure and performance properties of three model boride layers: iron–nickel boride layers of the Fe-Ni-B and Fe-Ni-B-P types, and reference iron Fe-B-type boride layer. It was demonstrated that the new variant of hybrid treatment produces Fe-Ni-B layers with the highest thickness, slight porosity, the optimal structure of Ni2B boride in the near-surface zone and the best performance properties. These layers show good adhesion, a much higher hardness of 2200 HV0.05 and near-surface compressive stresses of −450 MPa. Fe-Ni-B-P layers show slightly better wear resistance for higher loads, but like Fe-B layers, they are susceptible to spalling. It was demonstrated that Fe-Ni-B layers produced using boriding with nickel galvanic steel precoating could find application in heavy-duty elements of nanobainitic steel processing.

Fe2B layer growth kinetics on ASTM A307 steel evaluated by two diffusion models

Abstract In this study, we implemented two simple models to simulate the growth of the Fe2B layer on ASTM A307 steel through boriding. The first model considered steady-state boron diffusion, while the second model incorporated transient regime effects. In the steady-state model, the boron concentration profile within the Fe2B layer exhibited linearity. By correlating the boron chemical potential with the inward mass flux at the (Fe2B/substrate) interface, we confirmed the parabolic nature of layer growth. Both models were employed to determine the boron activation energies, yielding the same value of approximately 164 kJ mol−1. Experimental validation of the two models was conducted under two additional boriding conditions (1323 K for 1.5 and 2 h). Finally, the simulated layer thicknesses matched with the experimental values.

Solid particle erosion resistance of borided AISI D2 steel

Powder-pack boriding process was conducted on AISI D2 tool steel to improve its solid particle erosion resistance when compared to hardened and tempered (H&T) AISI D2 steel. FeB and Fe2B layers with thicknesses of 49 ± 6 μm and 44 ± 7 μm, respectively, were obtained. Erosion resistance was evaluated at different impingement angles at room temperature (RT) and 400 ºC using alumina particles. Novel results show that borided AISI D2 steel performs significantly better than H&T AISI D2 steel at impingement angles of 15º, 30º and 60º at both RT and 400 ºC, with reductions up to 81% in mass loss. However, at 90º, mass loss for borided AISI D2 steel is significantly higher. Mass loss in H&T AISI D2 steel is generated by progressive cutting and microforging, whereas in the borided AISI D2 steel it is generated by cracking and fracture.

Investigation of the influence of Fe2B layer thickness on the enhancement of tribological behavior of borided EN-GJL-250 cast iron: a comprehensive investigation under optimized lubrication

Investigation of the influence of Fe2B layer thickness on the enhancement of tribological behavior of borided EN-GJL-250 cast iron: a comprehensive investigation under optimized lubrication

Modelling boron diffusion for Fe2B layer formation: comparative kinetics analysis in pack-boronized AISI 4147 steel

Abstract In this current research paper, the modelling of boron diffusion during the powder-pack boronizing was achieved by utilizing two kinetics approaches: the integral method and average diffusion coefficient (ADC) method. This integral method used a general solution of algebraic differential equations (DAEs) system. The powders mixture composed of: 33.5 wt% B4C, 5.4 wt% KBF4 and 61.1 wt% SiC was employed to generate the Fe2B layers on AISI 4147 steel in the interval of 1123–1273 K for 2–8 h. The obtained surface layers have been characterized by Scanning electron microscopy (SEM) to examine the growth front with a typical saw-toothed morphology. The crystalline nature of boride phase has been verified by X-ray diffraction technique (XRD). The calculation results arising from the two models led to the similar boron activation energy in Fe2B equal to 196.19 kJ mol−1. Additionally, both models were checked out empirically by selecting three extra boronizing conditions obtained at 1273 K for increasing times (2.5, 4.5 and 8.5 h). The predicted layers’ thicknesses were found to be in line with the experimental results.

Characterizations and Kinetic Modelling of Boride Layers on Bohler K190 Steel

In this study, the Bohler K190 steel, manufactured by the powder metallurgy (PM) process, was subjected to the boronizing process. This thermochemical treatment was carried out in the range of 1173 to 1323 K, for 1–10 h. The scanning electron microscopy (SEM) was utilized for examining the morphology of layers’ interfaces with a dual-phase nature and measuring the layers’ thicknesses. The obtained boronized layers had a maximum thickness of 113 ± 4.5 µm. The X-ray diffraction analysis (XRD) confirmed the presence of FeB and Fe2B layers. The energy dispersive spectroscopy (EDS) mapping and EDS point analysis were used to investigate the redistribution of chemical elements within the boronized layers and the transition zone. The values of Vickers microhardness of Fe2B, FeB, and transition zone were estimated. Finally, the boron activation energies in FeB and Fe2B were found to be 204.54 and 196.67 kJ·mol−1 based on the integral method and compared to the literature results.

An experimental and modelling study on pulse current integrated CRTD-Bor process

In this study, pulse current integrated cathodic reduction and thermal diffusion-based boriding (PC/CRTD-Bor) process was applied to low carbon steels to grow industrially preferred single phase Fe2B layers in short durations (<1 h). For this purpose, the determination of combined effects of duty cycle and current density were examined at two sets of experiments as follows: (I) Duty cycle investigations where the specimens were borided at the constant current density of 200 mA/cm2 for different duty cycles (i.e., 1/8 - 1 s reduction & 7 s diffusion to 1/2 - 1 s reduction & 1 s diffusion) and (II) current density investigations where boriding trials were carried out at the constant duty cycle of 1/4 for different current densities (e.g., 50 mA/cm2 to 700 mA/cm2). Cross-sectional scanning electron microscope inspections along with X-ray diffraction analyses revealed that it is possible to grow a 20 μm thick Fe2B layer in 30 min at the condition of 1/4 duty cycle, 200 mA/cm2 current density and 950 °C. Additionally, the average diffusion coefficient model calculations were done which gave a good correlation with experimental results.

The influence of a pulsed-DC field on the growth of the Fe2B layer and the electrical behavior of the boriding media

Novel results about the growth kinetics of Fe2B layers produced by pulsed-DC powder-pack boriding (PDCPB) on AISI 1018 and 4140 steels were obtained. In the process, a DC-field is applied to ionize the B atoms and implements a programmable electronic control device (PECD) to maintain a constant B flux on both surfaces of the material. During PDCPB, the electrical resistivity (ER) was reduced due to the percolation of KBF4 in the boriding media. Nevertheless, the increase of ER was caused by the depletion of KBF4 after 1000s of the current induction. The PDCPB enhanced the growth kinetics of the Fe2B layer around of 9% for both borided steels compared to those estimated in the conventional powder-pack process.

Characterization and Boron Diffusion Kinetics on the Surface-Hardened Layers of Royalloy Steel

The Royalloy steel was boronized at 1173, 1223, 1248, 1273 or 1323 K for 1, 3, 5, 7 or 10 h using a Durborid powder mixture. The boronized samples were analyzed by scanning electron microscopy, X-ray diffraction and Vickers microhardness testing. The kinetic activity of boronized layers growth obeys the parabolic law, and the maximum thickness was 182 ± 10 µm. The thickness of FeB makes up to 40% of the total layer thickness. The obtained layers have two phases, which were composed of FeB and Fe2B phases, except for the sample boronized at 1173 K for 1 h which had an Fe2B layer only. The microhardness of the Fe2B phase had a range of 1370–1703 HV0.1, and that of the FeB phase was within 1727–2231 HV0.1. During the boronizing process, the chromium created extra particles with the highest amount of chromium in the transient region. The highest amount of silicon was observed at the boride layer/substrate interface. The amount of manganese was slightly lower in the boride layers compared to the amount in the substrate. Finally, the integral diffusion model was applied to determine the boron activation energies in the FeB and Fe2B layers, and this was followed by a comparison with the literature data.

Growth Kinetics, Microstructure Evolution, and Some Mechanical Properties of Boride Layers Produced on X165CrV12 Tool Steel

The powder-pack boriding technique with an open retort was used to form borided layers on X165CrV12 tool steel. The process was carried out at 1123, 1173, and 1223 K for 3, 6, and 9 h. As a result of boriding the high-chromium substrate, the produced layers consisted of three zones: an outer FeB layer, an inner Fe2B layer, and a transition zone, below which the substrate material was present. Depending on the applied parameters of boriding, the total thickness of the borided layers ranged from 12.45 to 78.76 µm. The increased temperature, as well as longer duration, was accompanied by an increase in the thickness of the FeB zone and the total layer thickness. The integral diffusion model was utilized to kinetically describe the time evolution of the thickness of the FeB and (FeB + Fe2B) layers grown on the surface of powder-pack borided X165CrV12 steel. The activation energy of boron for the FeB phase was lower than that for the Fe2B phase. This suggested that the FeB phase could be formed before the Fe2B phase appeared in the microstructure. The high chromium concentration in X165CrV12 steel led to the formation of chromium borides in the borided layer, which increased the hardness (21.88 ± 1.35 GPa for FeB zone, 17.45 ± 1.20 GPa for Fe2B zone) and Young's modulus (386.27 ± 27.04 GPa for FeB zone, 339.75 ± 17.44 GPa for Fe2B zone). The presence of the transition zone resulted from the accumulation of chromium and carbon atoms at the interface between the tips of Fe2B needles and the substrate material. The presence of hard iron and chromium borides provided significant improvement in the wear resistance of X165CrV12 steel. The powder-pack borided steel was characterized by a four times lower mass wear intensity factor and nine times lower ratio of mass loss to the length or wear path compared to the non-borided material.

Comparison and Analysis of Diffusion Models: Growth Kinetics of Diiron Boride Layers on ASTM A283 Steel

Hard-coated surfacing of a few micrometers is widely applied to increase the efficiency of tools, e.g., for cutting, forming, and casting applications. Therefore, the base thermodiffusion surface treatment is a practical solution to these issues by hardening surface layers with interstitial elements such as carbon, nitrogen, and boron. In particular, within this study, the growth kinetics of an iron boride layer on ASTM 283 steel were investigated with two diffusion models of the powder-pack boriding technique in the temperature range of 1123-1273 K with different treatment periods. The first model, called the steady-state diffusion model, used the modified version of the mass balance equations at the Fe2B/substrate growth interface, the parabolic growth law, and the solution of Fick's second law without time dependence. At the same time, the second diffusion model was based on Goodman's method, also called the integral heat balance method. Afterward, the diffusion coefficient of boron in the Fe2B phase was calculated by fitting the experimental data to the models. Nevertheless, the estimated value for the activation energy of ASTM A238 steel in both diffusion models was coincident (168.2 kJ∙mol-1). A mathematical analysis was implemented by means of a power series (Taylor series) to explain this similarity. The SEM examinations showed a solid tendency to saw-tooth morphology at the growth interface with the formation of the Fe2B layer, whose presence was verified by XRD analysis. The tribological characterizations, including the tests of Rockwell-C indentation, pin-on-disc, and Vickers hardness test method, were used to analyze the antiwear features of the Fe2B layers. Finally, this value of energy was compared to the literature for its experimental validation.

Structural and Magnetic Specificities of Fe-B Thin Films Obtained by Thermionic Vacuum Arc and Magnetron Sputtering

Fe-B based compounds are of high interest due to their special properties and the wide range of involved applications. While B is the element that facilitates the increase in the hardness and the degree of wear resistance, it is also an effective glass former, controlling the formation of a much-desired amorphous structure with specific magnetic properties. Major difficulties related to the proper engineering of Fe-B thin films lay especially in their preparation under well-defined compositions, which in turn, should be accurately determined. The present study closely analyzes the morpho-structural and magnetic properties of thin coatings of Fe-B of approximately 100 nm thickness and with the nominal B content ranging from 5 at. % to 50 at. %. The comparison between films obtained by two preparation methods, namely, the thermionic vacuum arc and the magnetron sputtering is envisaged. Morpho-structural properties were highlighted using X-ray diffraction supplemented with X-ray reflectometry and scanning electron microscopy, whereas the elemental investigations were performed by X-ray dispersive spectroscopy and Rutherford back-scattering spectroscopy. The magnetic properties of the Fe-B layers were carefully investigated by the vectorial magneto-optic Kerr effect and conversion electron Mössbauer spectroscopy. The high capability of Mössbauer Spectroscopy to provide the phase composition and the B content in the formed Fe-B intermetallic films was proven, in correlation to Rutherford back-scattering techniques, and to explain their magnetic properties, including the magnetic texture of interest in many applications, in correlation with longitudinal magneto-optic-Kerr-effect-based techniques.

TiN Coating and Fe2B Layer Obtained by PVD and Powder-pack Boriding Treatments Formed on ASTM A1011 Steel

TiN Coating and Fe2B Layer Obtained by PVD and Powder-pack Boriding Treatments Formed on ASTM A1011 Steel

The Supported Boro-Additive Effect for the Selective Recovery of Dy Elements from Rare-Earth-Elements-Based Magnets.

Liquid metal extraction (LME) for recycling rare-earth elements from magnets is studied, in the present study, to examine its suitability as an environmentally friendly alternative for a circular economy. While Nd (neodymium) extraction efficiency can easily reach almost 100%, based on the high reactivity of Mg (magnesium), Dy (dysprosium) extraction has been limited because of the Dy–Fe intermetallic phase as the main extractive bottleneck. In the present paper, the boro-additive effect is designed thermodynamically and examined in the ternary and quinary systems to improve the selectivity of recovery. Based on the strong chemical affinity between B (boron) and Fe, the effect of excess boron, which is produced by the depletion of B in FeB by Mg, successfully resulted in the formation of Fe2B instead of Dy–Fe bonding. However, the growth of the Fe2B layer, which is the reason for the isolated Mg, leads to the production of other byproducts, rare-earth borides (RB4, R = Nd and Dy), as the side effect. By adjusting the ratio of FeB, the extraction efficiency of Dy over 12 h with FeB addition is improved to 80%, which is almost the same extraction efficiency of the conventional LME process over 24 h.

MORPHOLOGICAL BEHAVIOR OF FEB AND FE2B IN BORIDE LAYER OF 304 STAINLESS STEEL UNDER DIFFERENT MEDIUM

This study investigates the morphological behavior of FeB and Fe2B phase in boronized 304 stainless steel under two different mediums which is powder and paste. Surface attrition was implemented in order to initiate better boron diffusivity. The comparison of microstructure in term of grain size and boride layer thickness were also analyzed. Scanning electron microscopy, X-Ray diffraction analysis and energy dispersive X-Ray Analysis were conducted to prove the existence of FeB and Fe2B phases. The relationship between the phase and Vickers microhardness was also investigated. The results show formation of flat-toothed boride layer in both sample with different FeB and Fe2B layer uniformity. Paste boronized sample with120 µm boride layer thickness had outperformed the powder boronized sample that with 43 µm boride layer thickness, thus providing significant improvement in microhardness values from 1500 Hv to 1800 Hv. In conclusion, paste medium provide outstanding boride layer thickness with 300% enhancement and excellent microhardness with 20% improvement. The results of this findings could offer a new insight in pack boronizing of stainless steel that can be complicated to boronized due to its high alloying element content.

Growth kinetics of diiron boride (Fe2B) layer on a carbon steel by four approaches

Abstract The pack-boriding kinetics of SAE 1020 steel has been addressed through utilizing four mathematical approaches in case of the formation of diiron boride layers. The values of boron diffusivities and activation energies in Fe2B were assessed in the interval of 1123 to 1223 K by using four models. Finally, the four models were experimentally verified by comparing the predicted results to the experimental value of Fe2B layer thickness determined at 1198 K for 6 hours. Finally, the simulated layers’ thicknesses agreed with the experimental result. In addition, similarities and differences observed in the models were also discussed.

The role of the carbon diffusion zone presence for the fracture toughness and wear resistance of a single-phase Fe2B layer produced on pure iron by gas boriding in N2–H2–B(CH3O)3 atmosphere

The aim of this work was to indicate the importance of the presence of the carbon diffusion zone on the fracture toughness of Fe2B layer. Single-phase Fe2B layer was produced as a result of gas boriding processes and simultaneous gas borocarburizing processes. The continuous gaseous processes were carried out at 1223 K for 2 h in N2–H2–B(CH3O)3 atmosphere. The temperature of trimethyl borate influenced its concentration in the gas atmosphere, therefore it was possible to carry out the two types of process: boriding and borocarburizing. As a result, in the case of the borided sample, the area directly of the Fe2B layer contained ferrite. Whereas, in the case of the borocarburized sample, pearlite grains appeared beneath the iron borides layer. Fracture toughness measurements were performed on the top surface of the specimens using a Vickers indenter under a load range from 0.981 N to 4.905 N. Both borided and borocarburized layers represent ceramic materials with a radial-median cracking mode. In the case of application of an indentation load lower than 3.924 N, an increase in indentation load from 0.981 N to 3.924 N resulted in increased fracture toughness. Whereas, a further increase in the load to 4.905 N was the reason for KC diminishing. In the case of high indentation load, the presence of a carbon diffusion zone in the gas borocarburized sample caused an increase in fracture toughness by about 50% compared to the gas-borided sample. The iron boride layers produced by gas boriding and simultaneous gas borocarburizing provided higher wear resistance in comparison to the pure iron without thermo-chemical surface treatment.