Abstract: Fine TiB dispersed Ti–6Al–4V alloy composites were developed using a powder metallurgy method, in which high hardness, high strength, high wear resistance and superplasticity were expected. Boride powder (i.e. TiB2), MoB, CrB and Ti–6Al–4V prealloyed powder were mechanically blended in a high energy ball mill. The powder obtained was pressed into dies and consolidated by reaction sintering. The dispersed boride particles produced reactive TiB in the matrix during sintering. In the hot isostatic press (HIP) which followed, samples showed a very fine microstructure of TiB dispersing homogeneously. At room temperature, hardness, compressive strength and wear resistance had the tendency to increase as blended boride content increases. The results of compressive and tensile test at 1173 K, in the strain rate range of 1×10−3–1×10−4 s−1, showed that TiB dispersed composites exhibited m values of no less than 0.38 and large elongation and superplasticity was confirmed.

Abstract: The segregation behavior of boron at grain boundaries in two INCONEL 718+ based alloys with different B concentrations was studied. The alloys, one containing 11 ppm of B and the other 43 ppm, were homogenized at 1200 °C for 2 hours followed by water quenching and air cooling. A strong segregation of boron at grain boundaries was observed using secondary ion mass spectrometry after the heat treatment in both the alloys. The segregation was found mainly to be of nonequilibrium type. The homogenized samples were also annealed at 1050 °C for various lengths of time. During annealing, boride particles were observed to first form at grain boundaries and then to dissolve on continued annealing at 1050 °C. The mechanisms of segregation and desegregation of B are discussed.

Abstract: Pulse electrode surfacing (PES ) is an eVective process for depositing ultrahard, corrosion- and erosion-resistant ceramic coatings on metals. In the present work, a titanium diboride coating deposited on 1018 steel using PES technique has been investigated. An attempt has been made to correlate the thermodynamic predictions and experimental observations. The role of the ceramic‐metal interface in the development of these coatings has been studied. A thick, adherent, metallurgically bonded and crack-free coating is obtained. It has been found that Fe intermixes with TiB 2 layer and acts as an excellent binder for TiB 2 .I t promotes the composite eVect of both hardness and toughness in these coatings and, hence, provides a crack-free coating with the sound interface. © 1998 Elsevier Science S.A.

Abstract: The new compounds Sc3Ir5B2 and Sc2MIr5B2with M = Be, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, or Ge were prepared by arc-melting appropriate compressed mixtures of the elemental components in an ...

Abstract: A boronized wear-resistant material that includes a boron-containing composition is disclosed. The boron-containing composition includes tungsten carbide and a compound represented by the formula W3MB3, where M is selected from the group consisting of iron, nickel, cobalt and alloys thereof. Particularly, a boride layer containing WC and W3CoB3 may be formed over a cemented tungsten carbide substrate by a suitable boronizing process. Additional compounds present in the boride layer include CoB, W2CoB2, and WB. A relatively thick and uniform boride layer may be obtained over a carbide substrate to form a wear-resistant body. Such a wear-resistant body may be used to manufacture cutting tools, drawing dies, inserts for an earth-boring bit, face seals, bearing surfaces, nozzles, and so on.

Abstract: Plasma-assisted bonding was carried out on low-alloy steels with no subsequent heat treating in order to provide a substitute for high-alloy steels. It was found that arcing in the glow discharge of a BCl 3 -H 2 -Ar atmosphere can be retarded by pulsed direct current power and the discharge current dropped greatly. The growth of boride layer was slower than that of conventional bonding and, in addition, the hardness was lower.

Abstract: A study on the quantification of the minor precipitates such as σ-phase, carbide and boride in UDIMET™ alloy720 (U720) and alloy720LI (U720LI) was carried out. A quantitative X-ray diffraction technique combined with electrolytic extraction has been used to quantify the micro-constituents. It was shown that U720LI is much less prone to σ formation than U720. At 800oC, the weight fraction of σ in U720LI remained at a level as low as ≈0.1%, even after 3000 h of exposure. In U720, on the contrary, it increased remarkably with exposure up to 1000 h and then saturated at ≈5%. A close examination of the σ formation mechanism using transmission electron microscopy (TEM), shows that σ forms and grows in consumption of γ′-phases. M23C6-type carbide and M3B2-type boride precipitates did not show any significant variations of amount in both alloys, U720LI and U720, during long time exposure at 800oC.

Abstract: The fracture mechanism of Fe–40 at.% Al matrix composites reinforced with ceramic particles and continuous fibers was investigated to clarify the primary factor governing their mechanical properties. Composites with carbide, boride and oxide reinforcements can be successfully fabricated by reactive hot-pressing. The fracture toughness of the composites with several types of fine particles decreases with an increase of yield strength due to the suppression of ability of plastic deformation. The environmental effect, which is the hydrogen embrittlement originated from moisture in air, further influences their fracture toughness. The environmental embrittlement of the composites can be reduced by micro-alloying with B and the addition of boride particles. On the other hand, the bearing of load by the fibers during the multiple-fracture behavior can significantly contribute to the improvement of fracture strength for the composites reinforced with Al2O3 continuous fibers. The composites completely fracture by the crack propagation from cracks in the fractured fibers. The fracture resistance of the matrix against the crack propagation also depends on the environmental effect. Therefore the optimization of the matrix properties by alloying techniques is an indispensable problem for the composite design of Fe–40 at.% Al alloys. ©1998 Elsevier Science S.A. All rights reserved.

Abstract: Ohmic contacts have been fabricated on p-type 6H-SiC using CrB2. Two hundred nanometer thick films were sputter-deposited on substrates of doping concentration 1.3×1019 cm−3 in a system with a base pressure of 3×10−7 Torr. Specific contact resistances were measured using the linear transmission line method, and the physical properties of the contacts were examined using Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, and transmission electron microscopy. The as-deposited CrB2 contacts exhibited rectifying characteristics and contained oxygen as a major contaminant. Ohmic behavior with linear current-voltage characteristics was observed following short anneals at 1100°C for 2 min at a pressure of 5×10−7 Torr. The oxygen in the CrB2 films was removed by the annealing process, and the lowest value of the specific contact resistance (rc) measured at room temperature was 8.2×10−5 Ω-cm2. Longer anneals at 1100°C for 3.5 h and 1200°C for 2 h reduced the room temperature values of r to 1.4×10−5 Ω-cm2. A thin reaction region has been identified at the CrB2/SiC interface; however, the interface remains essentially stable. Thermal stressing at 300°C in vacuum for over 2200 h produced only a slight increase in the specific contact resistance. The low value of the specific contact resistance and the excellent high temperature stability of the CrB2/SiC interface make this contact a candidate for high power/high temperature SiC device applications.

Abstract: The title compound is not a hexaboride, as was believed for many years. It is therefore not surprising that its structure also contains a novelty: for the first time a pentagonal B7 bipyramid (shown on the right) has been identified as part of the framework of boron atoms in a solid-state compound.

Abstract: The effect of heat treatment on the microstructure of an extruded Fe-40Al-07C-05B (at%) alloy was investigated Four types of precipitates were found to be present in the B2 matrix in the as-extruded condition These were Fe 3 AlC 05 with the perovskite structure, Fe 2 B, a tetragonal boride with the CuAl 2 structure, graphite (free carbon), and a new tetragonal phase (v) that is likely coherent with the matrix In addition, fringe contrast was observed, both in the matrix and within the precipitates and is thought to arise from the presence of stacking faults The stability of these precipitates and the faults following various heat treatments was determined

Abstract: Borides are promising candidates for wear resistant materials. But poor sinterability and extreme brittleness of borides retarded the fabrication of bulk materials. This paper gives criteria for the development of boride base cermets. Reaction boronizing sintering developed by us is a novel strategy to form a ternary boride coexisting with a binder metal during sintering associated with liquid phase formation. This new sintering technique has successfully brought development of three ternary boride base cermets such as Mo2FeB2, Mo2NiB2 and WCoB base ones. This paper describes the sintering behavior, mechanical properties, microstructure and phase formation related with the alloying elements on Mo2NiB2 boride base cermets. This paper also illustrates Reitveld analysis results of the complex boride structure in the cermets.

Abstract: A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures The alloy can include alloying additions such as ≦10 at % W, Nb and/or Mo The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 03 to 2% W, up to 1% Mo and 01 to 03% B In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 002 to 008% B

Abstract: Magnetic nanocomposite materials including iron, rare earth elements, boron, refractory metal and, optionally, cobalt are disclosed. Neodymium and lanthanum are preferred rare earth elements. The amounts of Nd, La, B and refractory metal are controlled in order to produce both hard and soft magnetic phases, as well as a refractory metal boride precipitated phase. The refractory metal boride precipitates serve as grain refiners and substantially improve the magnetic properties of the nanocomposite materials. The materials are particularly suitable for making bonded magnets.

Abstract: The formation mechanism of aluminum borate in the combustion synthesis of Al2O3/B4C composite with Al, B2O3, and C as starting materials is proposed. Based on the formation mechanism, several approaches taken to eliminate them are discussed. The unconverted B2O3 is the major cause of the formation of 9Al2O3 · 2B2O3 when the reaction proceeds in the SHS mode. The amount of 9Al2O3 · 2B2O3 formed is very sensitive to the excess B2O3 to the stoichiometry 4Al + 2B2O3 + C and influenced by the size of B2O3 powder. The high dispersion of the reactants is helpful in prompting the thermite reaction to consume B2O3 and hence inhibiting the aluminum borate formation.

Abstract: Ohmic contacts have been fabricated on p-type 6H-SiC (1.3×1019 cm−3) using CrB2, W2B, and TiB2. The boride layers (∼100–200 nm) were sputter-deposited in a system with a base pressure of 3×10−7 Torr. Specific contact resistances were measured using the linear transmission line method, and the physical properties of the contacts were examined using Rutherford backscattering spectrometry. All as-deposited contacts exhibited rectifying characteristics. Ohmic behavior was observed following short anneals (2–10 min) at 1100°C and 5×10−7 Torr. Current-voltage characteristics were linear for CrB2 and W2B and quasi-linear for TiB2. The lowest values of the specific contact resistance (rc in Ω-cm2) measured at room temperature for CrB2 and W2B were 8.2×10−5 and 5.8×10−5, respectively. The specific contact resistance for TiB2 was not determined accurately. Longer anneals (30 min for W2B and 90 min for CrB2) reduced the room temperature values of rc to 6.1×10−5 for W2B and 1.9×10−5 for CrB2. Backscattering spectra revealed substantial concentrations of oxygen in all as-deposited boride films. The short anneal cycle removed the oxygen in the CrB2 films and reduced the concentration substantially in the W2B films; however, annealing had no affect on the oxygen concentration in the TiB2 films. The CrB2/SiC interface remained stable during annealing; i.e., Si and carbon were not observed in the boride layers after annealing. In contrast, W2B and TiB2 reacted with the SiC epilayers, and after annealing, Si and carbon were observed at the surface of each boride layer.

Abstract: There are developed the physical grounds of creation of the new type of advanced ceramic — ceramic composite materials based on eutectic mixtures of rare earth and transition metals boride phases. It is worked out the process of directional crystallization of such compositions, that results in “in-situ” formation of their specific real structure, consisted from single crystal matrix of rare earth boride, strengthened, also, by, regularly distributed into it, single crystal whiskers of transition metal boride. Received composites possess useful inherent matrix component properties simultaneously with high mechanical properties, that distinguish them from common ceramic materials. The main attention is paid to LaB6-ZrB2 system that could be of interest as thermal-shock resistant effective cathode material for electron-beam sources.

Abstract: Boriding has been employed with some success to increase the service life of commercial forging dies fabricated from the hot work steel AISI H13. This steel is poorly suited to the treatment, however, since an undesirable intermediate layer is formed between the hard boride coating and the core. In practice, a boride coating thickness well below that required for the application has been imposed by the need to minimise the thickness of this layer. An experimental study was undertaken with the aim of improving the effectiveness of a boriding treatment by engineering the subsurface of AISI H 13 steel. It was established that a carburising pretreatment markedly improved the microstructural features of the steel subsurface. The formation of the undesirable layer was completely inhibited within the range of boride thicknesses employed in commercial practice and severely limited at the higher thicknesses better suited to forging applications.

Abstract: The creation of high-strength heat-resistant alloys based on titanium is of great scientific interest. Double-phase titanium (α+β) alloys are widely used at present. The alloying sets for these alloys are mainly developed with the purpose of increasing their strength and heat resistance by solution strengthening of the phases with substitutional elements. However, the increasing strictness of the requirements on the level of their mechanical properties makes it necessary to create titanium alloys that, can be strengthened by the segregation of an intermetallic phase or chemical compounds. An important problem in the development of such alloys is the choice of the optimum composition and the attainment, of the requisite dispersity and uniformity of distribution of segregations of strengthening phases in the structure. In this connection, carbon and boron, poorly soluble in titanium and forming independent carbide and boride segregations, are of some interest as alloying additives to these alloys.

Abstract: Powder mixtures of FeB and CrB were compacted and then treated at 1000\(^\circ \)C under vacuum for 8 h in order to obtain information on the solid state reactivity of the monoborides, useful to clarify the growth mechanism of boride coatings on chromium steels and to optimize the conditions of the thermochemical process. The effects of diffusion phenomena are pointed out and the relevant mechanisms discussed.

Abstract: A connector element, comprising a metal core with an electrically conductive nonmetallic surface layer, is new. Preferred Features: The layer consists of carbon and/or electrically conductive ceramic, especially a boride, nitride or carbide ceramic.

Abstract: Nitrides (such as BN and TiN) are widely used in various industrial applications because of their excellent wear and corrosion resistance and their thermal and electronic properties. The structural and chemical features formed during plasma vapor deposition of Ti/TiN on BN substrates have been studied using synchrotron radiation near edge absorption spectroscopy (NEXAFS). Various phases of interest have been formed with different annealing temperatures. Diffusion of the nitridation and the interference from oxidation (e.g., TiO2) and boride formation are of particular concern. X-ray photoelectron spectroscopy and secondary ion mass spectroscopy measurements complement our NEXAFS data. Phase formation and chemical bonding between the coating and the substrate are shown to be determining factors for the microhardness.

Abstract: The industrial synthesis of cubic boron nitride is performed under high pressure and high temperature from the hexagonal phase with catalysts. Since it has been demonstrated that c-BN is the stable BN modification under standard conditions, there should also be a way to synthesize the superhard c-BN phase at normal or low pressure. To reach this goal growth conditions with high mobility for both the B and the N species have to be found. Melts containing Li/B/N could be a possible solvent to form c-BN analogous to the high-pressure synthesis, whereby Li3BN2 is acting as a solvent-catalyst. Under normal pressure possible interactions of two different c-BN samples with various phases from the ternary Li-B-N phase system were investigated at temperatures up to 950 °C. The following melts were applied: elemental lithium (Li), lithium fluoride (LiF), lithium nitride (Li3N), lithium boride (Li7B6), lithium boronitride (Li3BN2) and boronoxide (B2O3). After these melt treatments morphological and other changes of the c-BN crystals were examined by SEM, Raman spectroscopy and XRD.

Abstract: PROBLEM TO BE SOLVED: To provide an electrode for resistance welding in which the strength of the alloy is increased and the whole electrode is formed of the alloy by containing the prescribed quantity of W, Mo and K, and the service life is excellent even when it is used in the spot welding of a galvanized steel plate. SOLUTION: K of 10-100 ppm is added to the W-Mo alloy material having the composition consisting of, by weight, 5-95% W and the balance substantially Mo to form the whole electrode. K is added at least in one kind of mode of oxide, nitride, metallic K, carbide, and boride. K is added at least one kind of mode of oxide, nitride, metallic K, carbide and boride as the dope agent to the oxide powder consisting of W and Mo. The powder is heat-treated in the reducing atmosphere, the obtained powder is formed, sintered, and worked in the prescribed shape to manufacture an electrode for resistance welding.