Добірка наукової літератури з теми "TiB2/TiB(N)/Si3N4"

AbstractA hard composite coating was fabricated by laser alloying of the Co-Fe-Al+B4C-Si3N4 mixed powders on TA15 (Ti-6Al-2Zr-1Mo-1V) titanium alloy in an open system. The composite coating mainly consisted of γ-Co, TiB2, TiB, TiC0.3N0.7, SiC, Ti3Al, FeAl, and Co-Ti intermetallics. The TEM diffraction pattern results indicated that the orientation relationship between TiB2 and TiC0.3N0.7 was (1-20)TiB2//(2-20)TiC0.3N0.7 in such a coating. Furthermore, during the alloying process, a number of Mo and Zr entered into the molten pool from the substrate due to the dilution effect, which refined the microstructures of the composite coating and also increased the amorphous phase content.

The technology of the TiB2/TiB cladding layer addresses the issue of the insufficient wear resistance of cup-shaped parts composed of titanium alloy materials. In order to eliminate the cracking problem of laser cladding TiB2/Ti-based alloy, 30%TiB2/Ti-based alloy gradient coating was prepared on the surface of titanium alloy by laser cladding in this study. The results revealed that the microstructure of the matrix and the cladding layer is metallurgically bonded. The microstructures of the cladding layer appear as rod-like and coarse-grained features on the surface, and fine needle-like and small-grained morphologies inside. The fine needle-like TiB precipitated in situ from the melt has a flat interface with Ti and exhibits a low degree of interfacial mismatch, while the interface between small particle-like TiB and Ti is wavy and has a high degree of interfacial mismatch. The gradual increase in the amount of TiB is present from the surface to the bottom of the cladding layer, while the amount of unmelted TiB2 particles decreases. The chemical structure of the cladding layer is mainly presented as TiB2, TiB and α-Ti phases. The maximum hardness of the cladding layer is 725 HV0.2, where it is more than twice the hardness of the substrate. The fretting wear resistance of the cladding layer is better than that of the titanium alloy substrate under low loads (50 N–100 N), while a high load (more than 150 N) triggers a reverse outcome.

The microstructure and friction/wear properties of TiB2-C (carbon-doped TiB2) films in TiB2-C/SiC double layer films (SiC films as interlayer) deposited on Ti6Al4V alloy substrate using magnetron sputtering technique at room temperature were investigated. The results show that the TiB2-C films exhibited the microstructural characteristics with nano-scale particles (domains), and the doped-carbon presented in manner of sp3 C-C and sp2 C-C bonds i.e. DLC (diamond-like carbon). The interface between the substrate and the SiC films and the interface between the SiC films and the TiB2-C composite films both showed good adhesion, with obvious element diffusions. As sliding against Si3N4 (silicon nitride) balls (2 mm in radius) using ball-on-disc type wear tester at room temperature under Kokubo simulation body fluid (SBF) and 50g load, the TiB2 -C composite films exhibited the friction coefficient of about 0.14 and the specific wear rate of 10.710-6 mm3 m−1 N−1. It is believed that the superior friction properties of the TiB2-C films are due to the role of the doped-carbon.

TiB2-TiN composite films/SiC films (SiC films as interlayer) were deposited on biomedical titanium alloy (Ti6Al4V) through magnetron sputtering technique. The friction/wear behaviors of the TiB2-TiN composite films under Kokubo simulation body fluid (SBF) were investigated. The results show that as sliding against Si3N4 ball (4 mm in diameter) at 200g load, the TiB2-TiN composite films exhibited the superior friction/wear properties with the friction coefficient of 0.22, the special wear rate in the magnitude order of 10−6 mm3 m−1 N−1together without interface delaminating. It was found that the films exhibited navel adhesion to Ca and P elements in Kokubo SBF. The present results demonstrate the possibility of developing the surface modification procedure of combining superior wear resistance and good osseointegration for application of orthopaedic implants.

Dense p-type and n-type SiGe thermoelectric conversion units were fabricated with a double-layer electrode of W/TiB2 or W/MoSi2 by using glass encapsulation hot-isostatic-pressing process. The TiB2 and MoSi2 layers were used to prevent the chemical reaction between the tungsten and SiGe materials. Si3N4 ceramic particles were added into the electrode materials to reduce the mismatch of the thermal expansion between the electrode and the SiGe. Finite element analysis showed that the addition of 40 vol% Si3N4 into the TiB2 layer and 55 vol% Si3N4 into the MoSi2 layer reduced the thermal residual stress to a much lower value than the strength of individual layer. Sintered units had electrical resistivities of (1.5–2.0) × 10−3 Ω cm in the SiGe zone and 10−4 Ω cm in the electrodes. The comparison of the thermoelectric properties of the SiGe sintered with and without electrodes confirmed that the electrodes did not deteriorate the Seebeck coefficient of the SiGe alloys.

Ti (C,N)-TiB2-Al2O3 multiphase ceramic coatings were in-situ synthesized on a steel substrate by SHS reactive arc spray technique. The composition and microstructure of the coatings were characterized by X ray diffraction, scanning electron microscopy and energy dispersive spectrometry. The results showed that multiphase ceramic coatings, composed of TiB2, TiB, TiC0.3N0.7, TiN, Al2O3 and AlN, can be prepared with the reactive cored wires by SHS reactive arc spray. The coatings exhibit the typical layer microstructure, with discrete second phases distributed in the continuous base phase. The bonding strength between the coating and substrate is 18.9MPa. The micro-hardness and elastic modulus of the coatings are 4.91GPa and 461.4GPa, respectively. The abrasion resistance is 3 times more than that of the substrate.

A variety of superhard coatings with Vickers plastic hardness exceeding 40 GPa have been reported by several research groups during the last five years (for recent reviews see refs [1,2]). However, one has to distinguish between superhard nanocomposites, such as nc-TiN/a-Si3N4, nc-TiN/a-Si3N4/a- and nc-TiSi2, nc-(Ti1-xAlx)N/a-Si3N4, nc-TiN/TiB2, nc-TiN/BN, etc. where the high hardness originates from the nanostrucutre and, therefore, remains stable upon annealing to high temperatures [1], and coatings, such as CrN/Ni, ZrN/Ni, and others [2] in which the measured high hardness is due to a high compressive stress that is induced in the coatings due to energetic ion bombardment during their deposition (e.g., by magnetron sputtering). We also summarize the recent progress in the industrial applications of the superhard nanocomposite coatings on machining tools.

Authors have studied the interaction between high-melting compounds from various classes, such as transition-metal carbides, borides, nitrides, and silicides, and covalent-bonded B4C, SiC, Si3N4, AlN etc. (over 160 phase diagrams), ternary B4C-SiC-MedB2, SiC-TiC-TiB2and other eutectics, which is important for optimizing the sintering temperature, material design and prediction of properties of many materials for high temperature applications including wear, aggressive, impact and radiation conditions. A vast identified group of eutectics with number of components n ≥ 2 has reduced eutectic temperature Тeut.(in some sistems reducing reaches 1200 °C). Noted, that increasing of n suppresses grain growth, which is particularly important for developing nanostructured ceramics via pressureless sintering and for controlling the ceramic's performance. Multiphase ceramics (SiC-TiC-TiB2, B4C-SiC-MedB2, B4C-W2B5-MedB2, B4C-LnB6-MedB2, etc.) feature improved mechanical parameters and high wear and impact resistance.

Abstract In this study, mechanical and tribological properties of the borided dual-phase α + β type Ti6Al4V titanium alloy were examined. For this purpose, Ti6Al4V alloy samples were borided for 6 h at a temperature of 1100 °C by the powder-pack boriding process. As a result of boriding, a boride layer consisting of TiB2 with a thickness of max ∼25 µm and TiB phases with a thickness of max ∼10 µm was obtained on the Ti6Al4V sample surfaces. As a result of the boride layer’s nanoindentation tests carried out using the Berkovich indenter, it was found to have an elastic modulus of 534.255 GPa and a hardness of 36.537 GPa. Wear tests were carried out using the pin-on-disc method under a load of 10 N and with a sliding distance of 1000 m. Whereas the dominant type of wear in non-borided samples was abrasive wear, oxidative mild wear was generally observed in borided samples. In borided samples, as a result of becoming of surface smoother by hard asperities breaking and increasing the actual contact area, the friction coefficients increased. It was determined that with boriding, the wear performance of Ti6Al4V alloy improved ∼46.8 times against the Al2O3 counterpart and ∼4.57 times against WC-6Co counterpart.

Solar energy is the inexhaustible and abundant energy resources on the earth which can be a best substitute for the fossil fuels. Over the past couple of decades, all the solar technologies are rising very steadily in two main branches including photovoltaics and solar thermal. One of the major components of solar thermal system is receiver, which plays an important role to enhance the photo-thermal efficiency by absorbing maximum amount of solar radiation with a minimum heat loss. In this regard, our objective was to fabricate a spectrally selective absorber coating for receiver which should have a high absorptance of ≥ 0.95 in the solar spectrum (0.25-2.5 μm) and a low thermal emittance of ≤ 0.05 in the infrared region (2.5-25 μm). In addition, while considering the real field applications, these coatings should exhibit exceptional thermal (> 450 °C) and environmental stability in different operational conditions. In spite of the outstanding thermo-chemical and thermo-physical stability of the ultra-high temperature ceramics (UHTCs), there are only a few reports on the spectral selectivity of these materials. Therefore, in the first part, we have utilized DC and RF magnetron sputtering system to prepare TiB2/TiB(N)/Si3N4 -based multilayer absorber coating. A systematic investigation was carried out to understand the influence of various deposition parameters including target power, deposition time and reactive gas flow on the spectral selectivity of the coating. The optimal process parameters lead to a high absorptance of 0.964 and an emittance of 0.18. However, the film is inadequate in terms of environmental stability. We have subsequently developed W/WAlN/WAlON/Al2O3 -based multifunctional novel coating using magnetron sputtering. The rationale behind this specific coating design was based on good optical properties and high diffusion block ability of transition metal -based oxides and oxynitrides. The optimally fabricated coating has a superior spectral selectivity with a maximum absorptance of 0.958 and a low emittance of 0.08. Based on the extensive analysis using the transmission electron microscopy (TEM), phase modulated spectroscopic ellipsometry along with computational analysis, we have manifested that the optical constants of each layer decrease from substrate to surface of coating, leading to enhance the photo-thermal efficiency. A prolonged thermal annealing established that the spectral properties of the coating could be retained at 500 °C in air for 150 hrs, indicating a service durability of ~ 25 years. Also, the directional and hemispherical emissivity is not compromised during annealing at 500 °C in air and in vacuum for 12 hrs. It is noteworthy to mention that the recently conducted high temperature testing (30 cycles at 450°C) in simulated solar field environment at Sandia National Laboratory establishes excellent thermal shock resistance property of the coating. In summary, a broad spectrum of ceramic combinations as tandem absorber coatings was investigated, and attempts were made to demonstrate the governing physical phenomena to explain the origin of spectral selectivity of ceramic absorbers. This dissertation will also provide guidelines to develop multilayer ceramic absorber coating for high temperature photo-thermal conversion systems.