TiB2 Layer Research Articles

Kinetics simulation of TiB2 layers on the titanium alloy (Ti6Al4V) obtained by liquid boriding process

Kinetics simulation of TiB2 layers on the titanium alloy (Ti6Al4V) obtained by liquid boriding process

Characterization and Growth Kinetics of Borides Layers on Near-Alpha Titanium Alloys.

Pack boriding with CeO2 was performed on the powder metallurgical (PM) near-α type titanium alloy at a temperature of 1273-1373 K for 5-15 h followed by air cooling. The microstructure analysis showed that the boride layer on the surface of the alloy was mainly composed of a monolithic TiB2 outer layer, inner whisker TiB and sub-micron sized flake-like TiB layer. The growth kinetics of the TiB2 and TiB layers obeyed the parabolic diffusion model. The diffusion coefficient of boron in the boride layers obtained in the present study was well within the ranges reported in the literature. The activation energies of boron in the TiB2 and TiB layers during the pack boriding were estimated to be 166.4 kJ/mol and 122.8 kJ/mol, respectively. Friction tests showed that alloys borided at moderate temperatures and times had lower friction coefficients, which may have been due to the fine grain strengthening effect of TiB whiskers. The alloy borided at 1273 K for 10 h had a minimum friction coefficient of 0.73.

Analysis of solar absorption, degradation mechanism and thermal stability in air environments for SS/TiB2/Al2O3 spectrally selective absorber coating

The quest for high solar-thermal conversion efficiency and thermal stability is a significant challenge in the development of high-efficiency spectrally selectivity absorber coatings. A key aspect of this challenge is the creation of air-stabilized coatings, particularly crucial for scenarios involving unexpected vacuum loss or applications of concentrating solar power systems in air environments. In our study, TiB2 films own excellent spectral selectivity and thermal stability at air environment. In pursuit of revealing the absorption mechanism of the coating, the optical constants, absoption and transmission of the single TiB2 layer were measured. The result of analysis display that the TiB2 layer contribute the bulk of the sunlight absorption. Reflectance spectra of the SS/TiB2/Al2O3 coating was succeeding simulated by CODE software with the optical constant to fit the experimental spectra, which confirms the results obtained by spectroscopic ellipsometry. The solar-thermal conversion efficiency of the as-deposited coating could reach 88.9 % of 100 suns at 500 °C. After annealing at 300–500 °C, the absorbance and emittance of the coating change slightly. But after annealing at 600 °C, the changing surface morphology, increasing surface roughness, and oxidation reaction of TiB2 resulted in a decrease in the optical performance of the coating.

Topographical hard protective coating for joint replacement implants

Joint replacement surgery, essential for managing joint diseases, requires improvements in tribocorrosion performance to ensure surgical success and longevity of joint implants. Transition-metal light-element (TMLE) compound coatings, known for their high hardness and chemical stability, have been extensively researched and applied for surface protection of joint implants. However, these coatings typically lack a lubrication phase, leading to high friction coefficients and severe corrosion wear, which makes long-term effective protection challenging. A promising approach is to utilize the natural lubricating proteins present in body fluids, which are continuously available and can thus address long-term service issues of TMLE coatings. In this work, we utilized micro-arc oxidation (MAO) technology to develop an underlying morphology, then conformally deposited a TiB2 layer, resulting in a cratered dual-layer TiB2/MAO coating. This unique cratered dual-layer structure not only preserves the high hardness and wear resistance of TiB2 but also aims to (1) absorb wear particles to prevent abrasive wear and (2) increase surface energy to optimize protein lubrication capacity. Consequently, the TiB2/MAO coating exhibits low friction coefficients and wear rates in protein-containing simulated body fluids. Furthermore, the dual-layer TiB2/MAO coating demonstrates excellent corrosion resistance and biocompatibility. This dual-layer coating design synergistically combines the superior intrinsic properties of material with unique structural construction, while also harnessing continuously available external proteins as lubricants to further optimize performance, thereby introducing an advanced strategy for developing protective coatings for implant materials.

Characterization of Wear Resistance and Corrosion Resistance of Plasma Paste Borided Layers Produced on Pure Titanium.

Commercially pure titanium was plasma paste borided using various temperatures of the process. An increase in the boriding temperature resulted in an increase in the thickness of the borided layer. All the layers produced consisted of an outer compact TiB2 zone and an inner TiB zone in the form of whiskers penetrating into the substrate. The presence of hard titanium borides resulted in a significant increase in wear resistance compared to non-borided pure titanium. However, the thickness of the layer produced strongly influenced the wear behavior, in respect of the time required for complete destruction of the layer. Higher wear resistance was characteristic of the TiB2 layer due to its compact nature, whereas the specific morphology of TiB whiskers resulted in their lower wear resistance compared to the outer TiB2 layer. Plasma paste boriding of pure titanium also had an advantageous effect on corrosion resistance compared to non-borided pure titanium. Simultaneously, due to the higher thickness of TiB2 layer, the specimen borided at a higher temperature showed higher corrosion resistance.

Defect Engineering of Hexagonal MAB Phase Ti2InB2 as Anode of Lithium-Ion Battery with Excellent Cycling Stability.

Hexagonal MABphases （h-MAB） have attracted attention due to their potential to exfoliate into MBenes, similar to MXenes, which are predicted to be promising for Li-ion battery applications. However, the high cost of synthesizing MBenes poses challenges for their use in batteries. This study presents a novel approach where a simple ball-milling treatment is employed to enhance the purity of the h-MAB phase Ti2InB2 and introduce significant indium defects, resulting in improved conductivity and the creation of abundant active sites. The synthesized Ti2InB2 with indium defects (VIn-Ti2InB2) exhibits excellent electrochemical properties, particularly exceptional long-cycle stability at current densities of 5Ag-1 (5000 cycles, average capacity decay of 0.0018%) and 10Ag-1 (15000 cycles, average capacity decay of 0.093%). The charge storage mechanism of VIn-Ti2InB2, involving a dual redox reaction, is proposed, where defects promote the In-Li alloy reaction and a redox reaction with Li in the TiB layer. Finally, a Li-ion full cell demonstrates cycling stability at 0.5Ag-1 after 350 cycles. This work presents the first accessible and scalable application of VIn-Ti2InB2 as a Li-ion anode, unlocking a wealth of possibilities for sustainable electrochemical applications of h-MAB phases.

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.

Compactability Regularities Observed during Cold Uniaxial Pressing of Layered Powder Green Samples Based on Ti-Al-Nb-Mo-B and Ti-B

We determined the compactability regularities observed during the cold uniaxial pressing of layered powder green samples, taking into account factors such as composition, height, and number of Ti–B (TiB) and Ti–Al–Nb–Mo–B (TNM) layers. The following composition was chosen for the TNM layer at %: 51.85Ti–43Al–4Nb–1Mo–0.15B, while for the Ti-B layer we selected the composition wt %: Ti-B-(20, 30, 40) Ti. Green samples were made containing both 100 vol % TiB and TNM, and those taken in the following proportions, vol %: 70TiB/30TNM, 50TiB/50TNM, 30TiB/70TNM; multilayer green samples were studied in the following proportions, vol %: 35TiB/30TNM/35TiB, 25TiB/25TNM/25TiB/25TNM, 35TNM/30TiB/35TNM. Based on the obtained rheological data, we determined the rheological characteristics of the layered green samples, including compressibility modulus, compressibility coefficient, relaxation time, and limiting value of linear section deformation. These characteristics were found to vary depending on the composition, height, and number of layers. Our findings revealed that reducing the TNM content in the charge billet composition improves the compaction of powder materials under the given technological parameters of uniaxial cold pressing. Moreover, we observed that increasing the boron content and decreasing the amount of titanium in the Ti–B composition enhances the compactability of powder materials. We also established a relationship between the compaction pressure interval and the density of the layered powder green sample.

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.

Structures and formation mechanism of borides with varied morphologies in cast γ-TiAl alloys

Borides with varied morphologies and structures obtained by changing B content in as-cast Ti-45Al-2Mn-2Nb alloys are investigated. With the increase of B content, morphologies of borides change from curved to straight, and flake shape, ribbon shape, needle/rod shape, and blocky appear in turn. Curved boride particles have a lamellar structure composed of TiB2 and B2 layers, accompanied by the random appearance and distribution of Ti3B4 and Bf-TiB layers. Except for the absence of the B2 layer, straight needle-like and blocky boride particles have roughly the same structure as curved boride particles, revealing that the formation of curved boride particles is accompanied by divorced eutectic with the matrix and internal irregular eutectic, while no eutectics occurs in straight boride particles. The lack of B atoms during solidification in alloys with lower B content results in a less regular structure and higher stacking fault density of curved boride particles compared to straight boride particles in alloys with higher B content. In addition, some needle-like boride particles are observed to have pure B27-TiB structure without intergrowth. The difference in morphologies and structures can be attributed to the difference in formation mechanism and crystallographic structures of the borides.

Alternative approach for the growth of a TiB2/TiC multilayer on M2 steel using the duplex method: Cathodic arc physical vapor deposition and cathodic reduction and thermal diffusion boriding

An alternative approach for producing a hard TiB2/TiC multilayer on M2 high-speed steel was introduced by combining cathodic arc physical vapor deposition (CA-PVD) and cathodic reduction and thermal diffusion-based boriding (CRTD-Bor). In this regard, the CRTD-Bor process was applied on CA-PVD Ti-deposited M2 steel and the effects of boriding parameters (i.e., temperatures and durations) on multilayer growth were examined. During boriding, Ti coating on the substrate was converted into Ti-borides on the top surface and a TiC layer was simultaneously formed at the interface of the Ti deposit and the steel matrix. The growth of boride and carbide phases was found to obey the parabolic law. The pre-exponential factors (K0) and the activation energy (Q) values were calculated as 7.50 × 10−9 m2/s and 146.10 kJ/mol for TiB2 growth and 1.81 × 10−7 m2/s and 187.31 kJ/mol for TiC formations, respectively. Additionally, empirical equations for estimating the thicknesses of TiB2 and TiC layers were derived. The penetration depth-dependent hardness measurements revealed the TiB2 layer hardness as 41 ± 5 Gpa, which decreased gradually toward the TiB region (24 ± 2 GPa) and fell to 13 ± 1 GPa in the Ti-rich area. The hardness then increased to 20 ± 1 GPa with the contribution of the TiC layer adjacent to the substrate. This multilayer coating exhibited −5.5 to −4.5 GPa compressive stress and good adhesions (HF1) to the substrates. Also, the results of tribological tests indicated a sevenfold increase in wear resistance under dry sliding conditions.

How positioning of a hard ceramic TiB2 layer in Al/CuO multilayers can regulate the overall energy release behavior

This study reports on a new ternary thermite comprising of Al-TiB2/CuO multilayers, designed to take the advantage of high ignitability of titanium (Ti), high volumetric density of boron (B), and low melting point of aluminum (Al). Results demonstrate synergetic effects leading to an energetic layer outperforming its single fuel counterparts, Al/CuO or TiB2/CuO, while being safe to handle. The additive TiB2 not only lowers the ignition energy by 100%, but also enhances the burn rate by more than a factor of two compared to the single fuel samples (Al/CuO and TiB2/CuO). The thermite reaction sequences and synergy of Ti, B and Al oxidation, examined by thermo-analytical analyses coupled with X-ray spectroscopy and high-resolution electron energy loss spectroscopy, demonstrate the strong affinity of TiB2 to oxygen that catalyzes CuO decomposition at temperatures as low as 380 °C; followed by a dual-step TiB2 oxidation: first to TiO, and then to TiO2 led by a reaction limiting step of oxidizer availability. Finally, Al undergoes oxidation via liquid boron oxide as well as gaseous oxygen. This study also underlines the crucial effect of the nanolayer morphology in the thin-film technology: when Al is sputter-deposited onto the TiB2 layer, Al ions penetrate into the grain boundaries penalizing TiB2 reactivity. The results demonstrate the advantages of using TiB2 fuel to improve the ignitability and the combustion performance of Al based thermite and offer some means to finely tune the energetic properties.

Microstructure and wear properties of powder-pack borided Ti–5Al–2.5Sn alloy

The boride layer was prepared on the surface of Ti–5Al–2.5Sn alloy by powder-pack borided at 975–1075 °C for 20 h with a temperature interval of 25 °C, and surface morphology, phase composition, microstructure, hardness, and wear properties of the borided Ti–5Al–2.5Sn alloy were investigated. The crystal parameters of TiB2 phase in the boride layer at different boriding conditions were obtained from the Rietveld structure refinement of Ti–5Al–2.5Sn samples, and the theoretical hardness values of TiB2 were calculated using the first-principles calculations. The results indicate that the boride layer comprises the outer TiB2 layer and the inner TiB whisker, and TiB2 layer thickens and TiB whiskers coarsen with the increase of temperature. The hardness of TiB2 layer is related to the boriding temperature, the greater hardness of TiB2 layer corresponds to the higher boriding temperature, which is in good agreement with the theoretically predicted results. Ti–5Al–2.5Sn alloy borided at 1075 °C–20 h has the highest hardness and excellent wear resistance. Finally, wear mechanisms were also discussed, which is a combination of abrasive and adhesive wear.

Wire electrode of 5754 aluminum modified by PVD-thin film depositions

Manufacturers of welding wire electrodes for GMAW welding adapt the alloy compositions of welding wire electrodes in order to adjust the weld pool behavior and the properties of the weld. Additively manufactured components in various sizes and with complex structures and multi-axial stress states place diverse demands on the material. The filler wire can significantly influence the material properties. The approach shown here describes the possibility of coating welding wire electrodes by physical vapor deposition, which enables flexible adjustment of the welding material composition. The element content in the weld metal can be adjusted within certain limits via the coating thickness. In the arc, applied thin-film coatings with coating thicknesses < 1 µm pass into the molten phase together with the substrate wire electrode according to ISO 18273—S Al 5754 (AlMg3). Microalloying elements such as TiB2 or Ti added to the weld pool in this way change the composition and thus influence the microstructure in the weld metal. This results in a grain refinement of up to 46%, which in turn has a positive effect on hot cracking susceptibility. PVD-coated welding electrodes also show changes in arc characteristics. With increasing TiB2 layer thickness, the arc length decreases by up to 44%, while the arc current increases. The fusion penetration behavior changes from a narrow finger-shaped to a round fusion penetration.

The effect of alloying elements in Ti-5Mo-5V-8Cr-3Al alloy on growth kinetics of TiB whiskers in boride layer

As one of the important ways to improve surface properties of Ti alloys, the boride layer prepared by the pack boriding is closely related to the growth and morphology of TiB whiskers in the boride layer, whereas the growth and morphology of TiB whiskers are significantly affected by alloying elements in the alloys. This work systematically explored the effect of alloying elements in β-type Ti-5Mo-5V-8Cr-3Al Ti alloy on growth kinetics of TiB whiskers and thickness of the boride layer using experiment and first-principles investigations. After boriding, an outer TiB2 layer and an inner TiB whisker + Ti layer are formed on Ti surface. TiB/β-Ti interface herein is non-coherent with the orientation relationships of (011)TiB//(1¯1¯ 0)β-Ti and [1¯ 00]TiB//[1¯ 11]β-Ti. Alloying elements segregated at the interface can increase diffusion energy barrier and slow down diffusion rate of active [B] atoms, and further reduce growth rate of TiB whiskers. Finally, a theoretical model for the boride layer growth on Ti surface was proposed.

Tribocorrosion and corrosion behavior of double borided layers formed on Ti-6Al-4V alloy: An approach for applications to bio-implants

TiB2 and TiB double layers were formed on surface of Ti-6Al-4V by a diffusional process at 850 ͦC for 4–16 h. EIS and XPS analyses revealed that formation of a passive film on the coated samples in a PBS solution increased corrosion resistance of Ti-6Al-4V. Tribocorrosion rate of the borided samples decreased up to 40 times compared with Ti-6Al-4V under a reciprocating condition and normal loads of 0.5–15 N against an alumina ball. The presence of B2O3/H3BO3 tribofilm on the borided samples led to a lower coefficient of friction and a more stable fluctuation of OCP.

Adhesive assisted TiB2 coating effects on friction stir welded joints

Friction stir welding is a novel technique for joining ferrous and non-ferrous materials in a solid state. The groove fill techniques are most popular and generally used by researchers to dope reinforcement in the FSWed zone to improve the properties of joints. The main drawback of this technique is that a few amounts of reinforcement material come out from the groove during the fabrication of the joint. In the present work, the adhesive-assisted reinforcement technique was used to overcome this problem for the fabrication of particulates reinforced friction stirred weld joint. In the present work, the aluminum alloy plate edges were coated with a thin layer of TiB2. The coated and non-coated edge plates were joined using friction stir welding at the rotational speed of 1400 and 2240 rpm, and welding speed of 32 mm/min using a taper threaded pin tool. The tensile strength of coated edge plate welded joints was found highest in comparison to non-coated joints which was 39.74% superior. The percentage elongation of coated edge joint was observed about 1.5 times lower than the non-coated edge plate joint. The flexure strength of TiB2 reinforced coated edge joint was found about 1.5 times higher. However, the impact strength of coated edge plate was found nearly three times lower than the uncoated edge joints. The TiB2 coated edge joints reveal 22.75% higher hardness than the non-coated edge plate joints welded at the rotational speed of 2240.

Critical current properties of an ex-situ MgB[formula omitted]/TiB[formula omitted] sample fabricated by spark plasma sintering using MgB[formula omitted] powder containing TiB[formula omitted

A critical current density, Jc, of an in-situ processed MgB2 is known to be improved by doping or adding Ti, in which Ti does not substitute for Mg-site but rather creates a thin layer of TiB2 on the surface of the MgB2 grain. For this study, we fabricated the in-situ (1−x)MgB2/xTiB2 samples from the mixture of (Mg1−xTixB2) (x=0 and 0.1), and then confirmed that the Jc of the Ti10% (x=0.1) sample was higher than that of the pristine (x=0) sample. To obtain a higher Jc(B), we prepared the dense ex-situ (1−x)MgB2/xTiB2 samples using a spark plasma sintering (SPS) method from the above powdered (1−x)MgB2/xTiB2 precursors. Contrary to the in-situ samples, the ex-situ Ti10% sample showed a degraded Jc compared to the ex-situ pristine sample. The microstructural analysis revealed that the grain growth of MgB2 occurred in the ex-situ Ti10% sample, which identifies the decrease of the number density of grain boundaries acting as the predominant pinning centers. We propose a possible mechanism that the TiB2 in the in-situ precursor powder promoted grain growth for the ex-situ Ti10% sample during the SPS process.

An investigation of the influence of the coating on the tool lifetime and surface quality for ultra-small micro end mills with different diameters

Micro milling tools are subjected to high abrasive wear and the probability of tool breakage rises with the decrease in tool diameter. Coatings can help to counteract abrasive wear and to increase tool life. In this paper, micro milling tools with diameters of 50 μm, 25 μm, 12.5 μm and 6 μm are coated with a 200 nm thick TiB2 layer and applied to machine commercially pure titanium. The achieved feed travel as well as the slot bottom quality is evaluated qualitatively and the roughness quantitatively via confocal microscopy. For the first time, ultra-small micro end mills with diameters below 50 μm were able to fabricate microstructures in commercially pure titanium in a robust process. Results show that a superior tool life can be achieved via coating, especially for the smallest diameters. This enables a more productive generation of ultra-small microstructures.

Microstructure and high-temperature oxidation behaviors of surface layer on TA2 pure titanium by boriding and aluminizing two-steps method

The surface layer on pure TA2 titanium was manufactured using boriding and aluminizing two-step methods. High-temperature oxidation experiments were carried out at 600 °C, 700 °C, and 800 °C for 100 h. Microstructure characterization of the surface layer was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). After 1050°C-4 h boriding and 1050°C-4 h aluminizing, the composite layer from the surface to the matrix consists of a TiB2 layer, TiB whisker + Al3Ti layer, Al3Ti layer, and diffusion layer. The Al3Ti layer could effectively protect the matrix, and thus, the borided and aluminized pure titanium shows excellent high-temperature oxidation resistance.