Boride Layer Research Articles

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.

Insight into tribocorrosion resistance and tribofilm formation on titanium boride coatings in a phosphate buffer saline solution

TiB2+TiB coatings were formed on Ti–6Al–4V through a molten-salt diffusional process at temperatures of 850 °C and 900 °C for 16 h. The thickness of the TiB layer increased by about two times at the higher process temperature, while the thickness of the TiB2 layer remained constant. Tribocorrosion rate of Ti–6Al–4V and the coated samples was evaluated in a reciprocating sliding under a normal load of 15 N in a phosphate buffer saline (PBS) solution for 3600–36000 cycles against an alumina ball. The results showed that the tribocorrosion rate of the borided samples decreased up to 56 times compared with Ti–6Al–4V after 36000 cycles. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies showed the presence of oxide-rich patches on the wear surface of Ti–6Al–4V with a thickness of up to 1 μm. TEM and atomic force microscopy (AFM) images also revealed the presence of a tribofilm with a thickness of up to 200 nm on the surface of the boride coating. In addition, X-ray photoelectron spectroscopy (XPS) analysis confirmed the tribofilm formed on the wear surface of coated samples contained B2O3/H3BO3 compound, resulting in a more stable fluctuation in coefficient of friction and open circuit potential during sliding. The SEM images of the alumina wear surface showed cracks and titanium transfer layers in contact with the borided layers and Ti–6Al–4V, respectively.

Direct current field enhanced boronizing of stainless steels and predictive performance of diffusion kinetics, deep neural network, and adaptive neuro-fuzzy inference system on boride layer thickness

Direct current field enhanced boronizing of stainless steels and predictive performance of diffusion kinetics, deep neural network, and adaptive neuro-fuzzy inference system on boride layer thickness

Research of Increase of the Wear Resistance of Machine Parts and Tools by Surface Alloying

The work scientifically substantiates the application of an effective technology for increasing the wear resistance of machine parts and tools due to complex diffusion saturation of the surface layer of parts made of iron-carbon alloys in the process of casting on gasified models based on the optimization of the composition of saturating mixtures and the establishment of patterns of structure formation.
 The possibility of strengthening the surface of castings from cast iron SCH20 and steels of various composition (25L, 30L, 35L, 45L, 25HL, 110H13L), obtained by methods of casting in an open mold and on gasified models, has been established. It is shown that the diffusion boride layer on 35L steel, obtained during casting, has an order of magnitude greater thickness (up to 5 mm) compared to the diffusion layers obtained by chemical-thermal treatment methods (up to 0.25 mm). Analytical dependencies have been established that connect the components of the composition of the mixture (chromium boride (CrB2), boron carbide (B4C), graphite, bentonite, sodium fluoride (NaF)), which saturates, with wear resistance and the thickness of the diffusion layer after hardening in the process of obtaining a casting by the method of casting on gasified models.
 A new composition of the saturating medium has been developed for surface strengthening in the production of cast parts from gray iron, carbon and alloy steels by simultaneous saturation with boron and chromium, containing chromium boride, boron carbide, graphite, bentonite, sodium fluoride (50-60 wt. % B4C + 20-25 wt. % CrB2 + 2-3 wt. % + 5-15 wt. % finely dispersed graphite + 5-7 wt. % bentonite). The application of the developed strengthening technology allows to improve operational properties, in particular, the wear resistance of machine parts and tools up to 25 times (compared to previously used methods), as well as to reduce the labor intensity of the strengthening process by up to 3.5 times.
 Tests of dies for pressing wood waste into briquettes made of 45L steel, strengthened with the help of the developed technology, showed that their stability increases more than 4.5 times compared to the previously used ones made of HVH steel strengthened by carbonitriding, and the use of the developed strengthening technology allows reduce the cost of manufacturing this part by 1.5 times.

Growth kinetics and corrosion properties of pack-borided Ti-5Al-2.5Sn alloy

In this work, the pack boriding method was used to treat the surface of Ti-5Al-2.5Sn (TA7) titanium alloy. The boriding temperatures were selected as 975 °C, 1000 °C, 1025 °C, 1050 °C, and 1075 °C, and the boriding time was 6, 8, 10, and 12 h. The phase and microstructure of the boride layer were analyzed using X-ray diffraction and scanning electron microscopy. The corrosion resistance was studied through polarization curves and electrochemical impedance spectroscopy, and the growth kinetics of the boride layer was modeled using the diffusion model of d2 = Dt and the parabolic model. After boriding at 1075 °C for 12 h, the thickness of the boride layer reaches the maximum with a maximum thickness of 45.75 μm. In addition, the diffusion model of d2 = Dt is more accurate in predicting the thickness of boride layer. The activation energies of boron diffusion in TiB2, TiB, and TiB2 + TiB layers are 94.78, 221.15, and 256.90 kJ/mol, respectively. Finally, the corrosion properties of borided TA7 alloy in NaCl and H2SO4 solutions were also discussed.

Investigation on microstructure and mechanical properties of boron-modified 13Cr5Ni2Mo by powder-pack boriding

ABSTRACT The main objective of the present paper is to investigate the effect of pack boriding treatment at 950°C/4 h on surface 13 Cr supermartensitic stainless steel. Scanning electron microscopy and X-ray diffractometry were used to characterise the grown boride layers microstructures. In addition, we performed 3D profilometry, microhardness measurements, nanoindentation tests with a Berkovich diamond tip, Daimler-Benz Rockwell-C adhesion, and ball-on-disk wear tests in order to evaluate the mechanical properties. After boriding, the phases were found to be iron borides (FeB/Fe2B), chromium borides (CrB), nickel borides (Ni2B), and molybdenum borides (Mo2B). The results showed that the use of the powder-pack boriding process on 13Cr SMSS at 950°C/4 h conducted in the presence of dual phases (FeB/Fe2B) improved the mechanical properties compared to untreated material.

Study on Microstructure of Pack-Borided GH4169 Alloy

The structure of the solid pack-boriding layer of nickel-based alloy is studied in this paper. The nickel-based alloy GH4169 was subjected to pack-boriding treatment at 850 °C and 950 °C, and the structure of the alloy boriding layer was studied. After the boriding treatment, a relatively continuous and uniform boriding layer was formed on the surface, which was mainly composed of nickel borides and chromium borides. The sample formed a layered structure of a boriding layer, diffusion zone, and substrate. After boriding treatment, Cr migrated to the surface to form CrB, Cr5B3, and Cr2B chromium borides, while Ni migrated to the lower part of the boriding layer to form Ni2B and Ni3B nickel borides.

Analysis of the Boronizing Process of High-vanadium Alloy Steel

The high-vanadium alloy steel substrate surface was carried out by solid powder boronizing. The results showed that a certain thickness and compact structure of the boronizing layers could be obtained after boronizing. The thickness of the boronizing layer was about –53 μm; the thickness of the transition zone was about –36 μm, and the boronizing layer was combined with the substrate firmly. The boronizing layers consist of FeB and embed into the substrate like a spider. The alloying elements have little effect on the formation of sawtooth morphology in the boride layers. The thickness of the boronizing layers increased with the boronizing time and temperature increase, and the thickness of the boronizing layer has a parabola relationship with the processing time.

High-temperature corrosion and oxidation properties of borided CoCrFeNiAl0.5Nb0.5 HEA

This study is focused on a detailed investigation of high-temperature corrosion and oxidation behavior of borided CoCrFeNiAl0.5Nb0.5 HEAs, considering their use in advanced engineering applications. CoCrFeNiAl0.5Nb0.5 HEA was produced by arc melting. XRD and SEM-EDS analysis before boriding determined that the alloy consisted of four different phases with different chemical compositions. Powder-pack boriding of a CoCrFeNiAl0.5Nb0.5 HEA was performed at 1000 °C for 3 h in a boriding media containing 90 % boron carbide and 10 % sodium tetrafluoroborate. As a result of the boriding process, complex boride layers consisting of (CoFe)B2, CrFeB, CoNbB, FeB and NiB phases were obtained on the surface with a thickness of 40 μm and hardness of 3004 HV. it was determined that the microstructure with cauliflower appearance evolved towards a dense and non-porous appearance around 20 μm as the boron diffusing into the HEA microstructure filling the gaps of intermetallic compound in the single structure, HEA and borided HEAs were each subjected to a cyclic hot corrosion test at 900 °C in molten corrosion salts of Na2SO4 and V2O5. After hot corrosion tests, long rod-like structures were observed in both samples due to the excessive corrosion, while borided alloys were more resistant to hot corrosion damage. After oxidation tests, HEA consists of a compact protective alumina scale that provided better oxidation resistance, while non-protective mixed oxides with cracks were dominant in the borided HEA.

Tribological Evaluation of Boride Layers Formed on an AISI M2 Steel Substrate by the Powder Packing Method.

Tribological Evaluation of Boride Layers Formed on an AISI M2 Steel Substrate by the Powder Packing Method.

A Comparative Study on Characterization and High-Temperature Wear Behaviors of Thermochemical Coatings Applied to Cobalt-Based Haynes 25 Superalloys

This study investigated the characteristic properties of aluminizing, boronizing, and boro-aluminizing coatings grown on Haynes 25 superalloys and their effects on the high-temperature wear behavior. The coating processes were conducted in a controlled atmosphere at 950 °C for 3 h. Characterization studies were performed using scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction analysis, nanoindentation testing, and high-temperature wear tests. It was determined that the thickness values of aluminide, boride, and boride–aluminide coatings were 140 ± 1.50 µm, 37.58 ± 2.85 µm, and 14.73 ± 1.71 µm, and their hardness values were 12.23 ± 0.9 GPa, 26.34 ± 2.33 GPa, and 23.46 ± 1.29 GPa, respectively. The hardness of the coatings resulted in reduced wear volume losses both at room temperature and at 500 °C. While the best wear resistance was obtained in the boronized sample at room temperature due to its high hardness, the best wear resistance at 500 °C was obtained in the boro-aluminized sample with the oxidation–reduction effect of Al content and the lubricating effect of B content in the boro-aluminide coating. This indicates that the presence of aluminum in boride layers improves the high-temperature wear resistance of boride coatings. The coated samples underwent abrasive wear at room temperature, whereas at 500 °C, the wear mechanism shifted to an oxidative-assisted adhesive wear mechanism.

Surface Growth of Boron Nitride Nanotubes through Boron Source Design

AbstractBoron nitride nanotubes (BNNTs) are promising materials due to their unique physical and chemical properties. Fabrication technologies based on gas‐phase reactions reduce the control and collection efficiency of BNNTs due to reactant and product dispersion within the reaction vessel. A surface growth method that allows for controllable growth of BNNTs in certain regions using a preburied boron source is introduced. This work leverages the high solubility of boron in metals to create a boronized layer on the surface which serves as the boron source to confine the growth of BNNTs. Dense and uniform BNNTs are obtained after loading catalysts onto the boronized substrate and annealing under ammonia. Confirmatory experiments demonstrate that the boride layer provides boron for BNNTs growth. Furthermore, the patterned growth of BNNTs is realized by patterning the boronizing region, demonstrating the controllability of this method. In addition, the Ni substrate with BNNTs growth exhibits better performance in corrosion resistance and thermal conductivity than pure Ni. This study introduces an alternative strategy for the surface growth of BNNTs based on boron source design, which offers new possibilities for the controllable preparation of BNNTs for various applications.

Influence of Surface Nanocrystallization on Two-Step Pack-Boronizing of AISI 5120 Steel

AISI 5120 steel, which underwent 30 min single-surface nanocrystallization via supersonic fine particle bombarding (SFPB), was pre-boronized at 600 °C for 2 h, and then final-boronized at 800 °C or 900 °C for 2–6 h, i.e., two-step pack-boronizing. The specimens’ microstructure and mechanical characteristics before and after two-step boronizing were examined in detail. The results showed that the hardness of the SFPB surface reached 570 HV, which was 2.73 times higher than its original hardness (209 HV). The nanocrystallized surface exhibited the increased thickness and hardness of the boride layer, in comparison to that of the un-SFPB surface. Two-step pack-boronizing further improved the thickness and hardness of the SFPB surface of AISI 5120 steel. When final-boronizing at 900 °C for 6 h, the thickness and hardness of the boronizing layer in the SFPB surface was 88 µm and 2196 HV, respectively, which was 10.5 times higher than the original hardness. Additionally, the CeO2 added in the boronizing agent was helpful in obtaining the boride layer with the ductile-serrated Fe2B phase rather than the brittle phase of FeB in the boride layer, which was expected for industrial applications.

Tribological investigations of boride layers on Ti6Al4V at room and elevated temperatures

PurposeThis paper aims to improve the wear resistance of titanium alloy using a high-hardness boride layer, which was fabricated on Ti6Al4V by a high-temperature boronizing process.Design/methodology/approachThe boride layers on Ti6Al4V were obtained at 1000°C for 5–15 h. Scanning electron microscopy, energy dispersive analysis and X-ray diffractometer were used to characterize the properties of the boride layer. The tribological performance of the boride layer at room and elevated temperatures was investigated.FindingsThe X-ray diffraction analysis showed that the boride layers were a dual-phase structure of TiB and TiB2. When the boronizing time increased from 5 h to 15 h, the microhardness increased from 1192 HV0.5 to 1619.8 HV0.5. At 25°C and elevated temperatures, the friction coefficients of the boride layers were higher than that of Ti6Al4V. The wear track areas of T-5 at 200°C and 400°C were 2.5 × 10–3 and 1.1 × 10–3 mm2, respectively, which were 6.1% and 2.6% of that of Ti6Al4V, indicating boride layer exhibited a significant wear resistance. The wear mechanisms of the boride layer transformed from slight peeling to oxidative wear and abrasive wear as the temperature was raised.Originality/valueThe findings provide an effective strategy for improving the wear resistance of Ti6Al4V and have important implications for the application of titanium alloy in a high-temperature field.

Boron capture stabilizing the diffusion barriers in a two-step Mo-Si-B coated refractory multi-principal element alloy

A Mo-Si-B based coating has been applied on a refractory multi-principal element alloy (RMPEA) using a two-step coating strategy and has endured more than 750 h of thermal cycling oxidation exposure between room temperature to 1300 °C with a minimal weight change. The formation of the Mo5SiB2 diffusion barrier in the coating prevents the inward diffusion of the coating components. Then, boron is captured by the RMPEA, resulting in the formation of a solid solution X5SiB2 (X = W, Mo, Ta, Nb, V) layer and an RMPEA-B boride layer underneath it that acts as the second diffusion barrier.

Improving Boride Layer Adhesion to AISI D2 Steel by Post-heat Treatments

Improving Boride Layer Adhesion to AISI D2 Steel by Post-heat Treatments

Effect of boriding on high temperature tribological behavior of CoCrMo alloy

In the present work, CoCrMo alloy surfaces were subjected to powder-pack boriding at 950 ℃ for 5-hour and 7-hour treatment periods. The obtained boride layers were characterized with scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, nanoindentation and high temperature wear tests. Characterization results show that boride layers are composed of CoB, Co2B, CrB and Co2MoB2 phases. Up to 4-fold increase is achieved in nanohardness values due to the boride layers in addition to increased elastic moduli. Increased surface hardness coupled with the high temperature stability of boride layers led to nearly 12, 7 and 10-fold increase in the wear resistance of CoCrMo alloys, worn at room temperature, 250 ℃ and 500 ℃, respectively.

Effect of Prior Boriding on Microstructure and Mechanical Properties of Nanobainitic X37CrMoV5-1 Hot-Work Tool Steel.

The influence of prior pack boriding on the microstructure and properties of nanobainitised X37CrMoV5-1 hot-work tool steel was investigated in the present work. Pack boriding was conducted at 950 °C for 4 h. Nanobainitising consisted of two-step isothermal quenching at 320 °C for 1 h, followed by annealing at 260 °C for 18 h. A combination of boriding with nanobainitising constituted a new hybrid treatment. The obtained material exhibited a hard borided layer (up to 1822 ± 226 HV0.05) and a strong (rupture strength 1233 ± 41 MPa) nanobainitic core. However, the presence of a borided layer decreased mechanical properties under tensile and impact load conditions (total elongation decreased by 95% and impact toughness by 92%). Compared with borided and conventionally quenched and tempered steel, the hybrid-treated material retained higher plasticity (total elongation higher by 80%) and higher impact toughness (higher by 21%). It was found that the boriding led to the redistribution of carbon and silicon atoms between the borided layer and substrate, which could influence bainitic transformation in the transition zone. Furthermore, the thermal cycle in the boriding process also influenced the phase transformations during subsequent nanobainitising.

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.

Wear properties of borided WC-Co

Abstract Today, artificially produced tungsten carbide (WC) tools are used as an alternative to diamonds such as mining, drilling, cutting, or machining. Although it is called WC, it also contains a certain amount of cobalt (Co). The most important reason for this is that it increases the wear resistance of the WC. Boriding is a type of surface hardening method that provides wear, hardness, and corrosion resistance to the applied surface. In boriding, which is a kind of diffusion process, there is no change in the dimensions of the materials since the boride layer grows from the outer surface of the materials to the inside. In this study, the development of surface properties by boriding of 90 wt% WC and 10 wt% Co-containing abrasive bits used for drilling were investigated. The samples were borided in an atmosphere-controlled furnace at 1173, 1273, and 1373 K for 1, 2, and 3 h by the pack boriding method. After the boriding processes, the microstructure, hardness, and chemical composition of the boride layers formed on the surface of the samples were examined, and finally, the wear tests were carried out to reveal the differences compared to the unborided sample.