Hardness and wear resistance of B4C ceramics prepared with several additives

Zorzi, J. E.; Perottoni, C. A.; Jornada, J. A. H. da

doi:10.1016/j.matlet.2005.04.047

Cited by 138 publications

(69 citation statements)

References 25 publications

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“…O resultado será a formação de uma cratera, cujo diâmetro é medido por microscopia óptica. A partir deste diâmetro, obtém-se o coeficiente de desgaste, K, definido como [40][41][42][43][44][45][46] K= pb…”

Section: Materiais E Métodosunclassified

Dureza e resistência ao desgaste da camada de ZrN formada por nitretação a plasma sobre zircônia parcialmente estabilizada com ítria

et al. 2010

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ResumoCorpos-de-prova de zircônia parcialmente estabilizada com ítria foram moldados por prensagem uniaxial, sinterizados e nitretados em plasma de micro-ondas à pressão atmosférica. A camada de ZrN sobre zircônia formou-se a uma taxa de 4 μm.min -1 , podendo atingir uma espessura de 500 μm. As amostras foram caracterizadas por meio de medidas de dureza e resistência ao desgaste. A superfície nitretada apresentou dureza superior e resistência ao desgaste similar ao substrato de zircônia. Palavras-chave: zircônia, nitreto de zircônio, resistência ao desgaste, dureza. Abstract Samples of yttria partially-stabilized zirconia were molded by uniaxial pressing, sintered and nitrided in an atmospheric

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Section: Materiais E Métodosunclassified

Dureza e resistência ao desgaste da camada de ZrN formada por nitretação a plasma sobre zircônia parcialmente estabilizada com ítria

et al. 2010

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“…Within a certain range, the higher the hardness of the material, the greater the wear resistance, therefore hardness is a very important measure. The problem of processing performance of gray cast iron cylinder liners has been gradually highlighted at present [2]. It is often found that the mechanical properties of domestic and imported cylinder liner are almost the same, but the wear of the tool is more serious during the processing, indicating that the microstructure of gray cast iron have a great impact on the mechanical properties and cutting performance.…”

Section: Introductionmentioning

confidence: 99%

Study on Cutting Performance of Gray Cast Iron Cylinder Liner

Wang¹,

Su²,

Zhao³

2017

dtetr

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Abstract. Cutting performance of gray cast iron cylinder has been valued in the recently years. The microstructures and mechanical properties of four sets of gray cast iron cylinder liners were compared and studied. At the same time, the effect of microstructure on the cutting performance was explored. It is concluded that uniform matrix of gray cast iron will improve the cutting performance, and the higher the graphite content, the finer the size, the better the cutting performance. Ultimately, the condition of gray cast iron with good mechanical properties and cutting performance is below: fine, curved, disordered and evenly distributed flaky graphite structure and large lamellar spacing and uniform pearlite matrix.

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“…high hardness, low density, high melting point, low wear coefficient, high chemical stability. Such properties thus make icosahedral boron-rich solids useful as, for instance light weight armor, wear-resistant materials, cutting tool materials [16][17][18][19], candidate materials for high temperature electronic [15,20] and thermoelectric devices [15,21,22], etc. Due to high absorption cross section for thermal neutron of the isotope 10 B, icosahedral boron-rich solids can be used as neutron absorbing materials in nuclear reactors [15,16,23,24].…”

Section: Introductionmentioning

confidence: 99%

First-principles study of configurational disorder in icosahedral boron-rich solids

Ektarawong¹

2015

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This thesis is a theoretical study of configurationally disordered icosahedral boronrich solids, in particular boron carbides, using density functional theory and alloy theory. The goal is to resolve discrepancies, regarding the properties of boron carbides, between experiments and previous theoretical calculations which have been a controversial issue in the field of icosahedral boron-rich solids. For instance, B 13 C 2 is observed experimentally to be a semiconductor, meanwhile electronic band structure calculations reveal a metallic character of B 13 C 2 due to its electron deficiency. In B 4 C, on the other hand, the experimentally observed band gap is unexpectedly smaller, not the usual larger, than that of standard DFT calculations. Another example is given by the existence of a small structural distortion in B 4 C, as predicted in theoretical calculations, which reduces the crystal symmetry from the experimentally observed rhombohedral (R3m) to the based-centered monoclinic (Cm). Since boron carbide is stable as a single-phase over a broad composition range (∼8-20 at.% C), substitution of boron and carbon atoms for one another is conceivable. For this reason, the discrepancies have been speculated in the literature, without a proof, to originate from configurational disorder induced by substitutional defects. However, owing to its complex atomic structure, represented by 12-atom icosahedra and 3-atom intericosahedral chains, a practical alloy theory method for direct calculations of the properties of the relevant configurations of disordered boron carbides, as well as for a thermodynamic assessment of their stability has been missing.In this thesis, a new approach, the superatom-special quasirandom structure (SA-SQS), has been developed. The approach allows one to model configurational disorder in boron carbide, induced by high concentrations of low-energy B/C substitutional defects. B 13 C 2 and B 4 C are the two stoichiometries, mainly considered in this study, as they are of particular importance and have been in focus in the literature. The results demonstrate that, from thermodynamic considerations, both B 13 C 2 and B 4 C configurationally disorder at high temperature. In the case of B 13 C 2 , the configurational disorder splits off some valence states into the band gap that in turn compensates the electron deficiency in ordered B 13 C 2 , thus resulting in a semiconducting character. As for B 4 C, the configurational disorder eliminates the monoclinic distortion, thus resulting in the restoration of the higher rhombohedral symmetry. Configurational disorder can also account for an exceliii iv lent agreement on elastic moduli of boron carbide between theory and experiment. Thus, several of the previous discrepancies between theory and experiments are resolved.Inspired by attempts to enhance the mechanical properties of boron suboxide by fabricating boron suboxide-boron carbide composites, as recently suggested in the literature, the SA-SQS approach is used for modeling mixtures of boron sub...

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Hardness and wear resistance of B4C ceramics prepared with several additives

Cited by 138 publications

References 25 publications

Dureza e resistência ao desgaste da camada de ZrN formada por nitretação a plasma sobre zircônia parcialmente estabilizada com ítria

Dureza e resistência ao desgaste da camada de ZrN formada por nitretação a plasma sobre zircônia parcialmente estabilizada com ítria

Study on Cutting Performance of Gray Cast Iron Cylinder Liner

First-principles study of configurational disorder in icosahedral boron-rich solids

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