Papers by Author: Paweł Rutkowski

Abstract: 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.

Abstract: The earlier studies showed that addition of different chromium carbides to nonstoichiometric fine titanium carbide improve sintering in the similar way. The phase, structural and microstructural changes for addition of various chromium carbides were also similar. In the present work the composite materials were made of various carbon quantity saturated titanium carbide (as matrix) and commercial chromium carbide Cr3C2 (as additive). The titanium carbide powders with variable content of carbon in structure were synthesized by the SHS method. The chromium carbide in quantity of 7.5 % by volume was added to the initial mixture. The influence of various stoichiometry of titanium carbide on onset temperature of sintering was examined by use of high temperature dilatometer. The phase and structural changes of examined materials during sintering were made using XRD and Rietveld method. The evolution of microstructure, versus of different stoichiometry titanium carbides, was observed by use of scanning electron microscopy.

Abstract: 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.