Authors: J. Abenojar, M.A. Martinez, Francisco Velasco
Abstract: Borides, especially transition metal borides, like Mo2FeB2 ternary boride, are promising
candidates for wear resistance applications. However, poor sinterability and extreme brittleness
raise difficulties to manufacture a structural material. In this work, the viability to obtain Fe-Mo-B
alloys with high wear resistance materials obtained by PM techniques is studied.
Other researchers use Cr and Ni alloyed steels and the B amount addition is very low. The main
objectives are to increase the amount of B, not to use Cr alloyed steels and to decrease the sintering
temperature. This can be obtained using mechanically alloyed Fe/B (50% by wt.) powders, which
are highly reactive after milling for 36 h.
The mixture has a composition of 40%Mo-40%Fe-20%Fe/B, being characterized by flow rate and
apparent density. These materials were uniaxially compacted and vacuum sintered. Specimens were
analysed by SEM and physical and mechanical properties were evaluated (density, dimensional
change, bending strength, hardness and wear).
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Authors: Ramazan Kayikci, Osman Kurtulus, Riza Gürbüz
Abstract: The formation of borides in an Al–3 wt.% B alloy produced from reaction between
aluminium and boron oxide (B2O3) has been investigated. Melting and cooling experiments were
carried out to explore the growth characteristics of aluminium boride crystals. During heating up
to1300 oC boron dissolved into molten aluminium and subsequently cooled to form solid aluminium
borides in the aluminium matrix. At room temperature boride particles was identified as AlB2.
Although, AlB12 phase is the first phase to form directly from the Al-B liquid above 1000 oC which
transforms to stable AlB2 crystals by a peritectic reaction during cooling. Scanning electron
microscope (SEM) and X-ray diffraction (XRD) techniques were employed. Results showed that
the shape and distribution of the borides are dependent on the cooling conditions of the liquid Al-B
alloy.
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Authors: Seung Jun Lee, Do Kyung Kim
Abstract: Zirconium diboride based composites containing silicon carbide with relative densities in excess of 99 % were produced by hot-pressing. Oxidation test was conducted in air at 1500 °C. ZrB2-SiC composite showed relatively low oxidation resistance due to the non-uniform surface silica-rich layer. But in case of mixed boride-SiC composites further improvement of the oxidation performance were observed due to the phase separation in the surface silica-rich layer.
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Authors: Jian Jun Zhang, Yi Min Gao, Jian Dong Xing, Sheng Qiang Ma, Wan Qin Yan, Jing Bo Yan
Abstract: Microstructure and properties of isothermally quenched high boron white cast iron were investigated in this paper. The results show that the microstructure of high boron white cast iron is mainly composed of many continuous and netlike eutectic borides, pearlite and ferrite under as-cast condition. The microhardness of Fe2B ranges in 1200-1600HV whose value seems to approximate that of (Fe,Cr)7C3–type carbide (HV1200~1800) in high chromium white cast iron. After isothermal quenching, the matrix transforms into lower bainite in which carbide precipitations are arranged in parallel rows at an angle of 60 deg to the long axis of the plates, but the morphology of boride remains nearly unchanged compared with its as-cast condition. Moreover, precipitation particles with the size of about 1~4 μm can be found in the matrix of isothermally quenched high boron white cast iron. Impact fracture morphology of isothermally quenched high boron white cast iron indicates that fracture propagated more easily through boride/matrix interface than through matrix.
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Authors: Matej Beznák, Alexander S. Chaus, Lubomír Čaplovič
Abstract: Diffusion boride layer has been produced on the surface of a hot work tool steel. The microstructure and elemental spectra as well as depth profiles of the elements in the boride layer have been studied by scanning electron microscopy, X-ray diffraction analysis and energy dispersive X-ray spectrometry. Micro-hardness measurement was carried out using the Vickers micro-hardness test. The results showed that the boride layer is formed by boron compound Fe2B. Additionally, boron carbide B4C has been revealed embedded in the bulk of the boride layer.
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