Gabriela Górny

Effect of carbon content on the microstructure and properties of silicon carbide-based sinters

The paper presents the results of investigations of the influence of carbon activator content on the microstructure and mechanical properties of silicon carbide sinters with 1, 3, and 6 wt.% of carbon.

Microstructure-property relationship in B4C-βSiC materials

Abstract The microstructure-property relationships have been studied in B 4 C-βSiC materials for boron contents from 0 to 30 wt.% (corresponding to a range from 0 to about 45 vol.% of B 4 C). The materials were produced by sintering or hot-pressing of composite BSiC powders synthesized by solid combustion. In order to characterise the microstructure quantitatively, observations of polished sections of the materials, etched by potassium salts, were made by using the scanning electron microscopy. After binarisation, the data were eventually subjected to image processing. For both coexisting phases (βSiC and B 4 C) the distribution and mean values of the following microstructural parameters were determined: grain area, grain aspect ratio and grain dimensions. The electrical resistivity and bending strength were also determined for the materials characterised microstructurally.

Effect of Processing Conditions on Microstructure of SiC-TiB2 Composite

The objective of the study as described in this paper is to analyse the effect of processing conditions as: volumetric content of TiB2 powders and the time of milling them on the parameters of microstructure of particulate composite with a SiC matrix and 10 or 20 vol.% of the TiB2 as dispersed phase. From the initial research conducted by the authors, as well as from the data contained in the reference literature, it is known that the SiC-TiB2 composite is a potential material to be applied in the manufacture of cutting tool inserts. To manufacture composites, SiC powders (Starck, UF-15) and TiB2 powders (Momentive, HCT-30) were used; they were milled for 15 or 30 h in a vibrating-rotating mill with silicon carbide balls as grinding media. The SiC-TiB2 composite was manufactured using a hot pressing method under the following conditions: temperature: 2120 oC; pressure: 25 MPa; and sintering time: 30 min. Under the stereological analysis of SiC-TiB2 some selected microstructural parameters were measured, i.e.: volume fraction of TiB2, average size of TiB2 particles, mean diameter of particles (D), shape factor of TiB2 particles, α, as well as NA and NV parameters that determine the quantity of TiB2 particles contained in the composite. Computer-aided analysis of microstructure of the SiC-TiB2 composites and analysis of results of measurements of mechanical properties of these composites prove their the microstructure and properties depend on the volumetric content of TiB2 dispersed phase, and this dependence is significant.

Ceramic Tool Materials for High Speed Cutting Process

Frictional and mechanical properties of hot-pressed Al2O3 and Si3N4 - matrix composites containing up to 5 vol. % hexagonal BN as a solid lubricant. A very low coefficient of friction which is necessary for high-speed cutting has been observed. Fracture toughness remained constant with increase of h-BN content while flexural strength changes with the hBN content have been found to depend upon the material homogeneity. The work has been supported by EU Funds in Poland under contract UDA-POIG.01.03-12-024/08-00.and has been realized in the frame of scientific-industrial consortium.

Description of the homogeneity of material microstructures: using computer-aided analysis

The paper presents and compares three methods for the quantitative description of particle spatial distribution, namely, the linear covariance, Radial Distribution Function (RDF) and tessellation methods. First, model structures were analysed using these methods. It was shown that the particle spatial distribution and the quantitative parameters are clearly interrelated. The presented methods were applied for a quantitative description of the structure of AlN-TiB2 composite obtained via Self-Propagation High-Temperature Synthesis (SHS). Several parameters quantitatively describing the particle spatial distribution in the studied material were determined. The influence of the structural parameters on mechanical properties was investigated. The results are discussed in terms of further optimisation of the studied material.