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This paper is devoted to the sintering process of Al 2 O 3 -SiO 2 -ZrO 2 ceramics. The studied method was electroconsolidation with directly applied electric current. This method provides substantial improvements to the mechanical properties of the sintered samples compared to the traditional sintering in the air. The research covered elemental and phase analysis of the samples, which revealed phase transition of high-alumina solid solutions into mullite and corundum. Zirconia was represented mainly by tetragonal phase, but monoclinic phase was present, too. Electroconsolidation enabled samples to reach a density of 3.0 g/cm 3 at 1300 °C, while the sample prepared by traditional sintering method obtained it only at 1700 °C. For the composite Al 2 O 3 -20 wt.% SiO 2 -10 wt.% ZrO 2 fabricated by electroconsolidation, it was demonstrated that fracture toughness was higher by 20-30%, and hardness was higher by 15-20% compared to that of samples sintered traditionally. Similarly, the samples fabricated by electroconsolidation exhibited elastic modulus E higher by 15-20%. The hypothesis was proposed that the difference in mechanical and physical properties could be attributed to the peculiarities of phase formation processes during electroconsolidation.

The paper presents and discusses questions on structure formation during the sintering process of Cr 2 O 3 -based composites using the hot pressing method, when a chemical reaction between the components takes place. The task was difficult because Cr 2 O 3 decomposes when sintered at temperatures above 1300 °C. The proposed novel method allowed for interaction between aluminum and chromia, thus avoiding the decomposition of the latter. Here, ultrafine aluminum powder played the role of the active agent forming a liquid phase and reacting with Cr 2 O 3 . The appearance of the solid solutions of (Cr,Al) 2 O 3 with different stoichiometry of Cr and Al depended on the aluminum content in the initial mixture. The solid solution significantly strengthened boundaries between composite phases, resulting in the composite material of high fracture toughness between 5 and 7 MPa m ½ and bending strength of ca. 500 MPa. The best mechanical properties exhibited the cermet with 22 wt.% of the restored chromium.

Fabrication of alumina-tungsten carbide nanocomposite was investigated. Characteristics of the densification and sintering were analyzed considering both the nano-size particle starting powders and the processing stages. Different heating rates were generated during densification and consolidation with a maximal load was applied only after a temperature of 1000 °C was reached. Due to the varying dominance of different physical processes affecting the grains, appropriate heating rates and pressure at different stages ensured that a structure with submicron grains was obtained. With directly applied alternating current, it was found that the proportion Al 2 O 3 (50 wt.%)-WC provided the highest fracture toughness, and a sintering temperature above 1600 °C was found to be disadvantageous. High heating rates and a short sintering time enabled the process to be completed in 12 min, saving energy and time.

The paper presents the results of investigations on the glass fiber reinforced composite for the floor panels with quartz powder additions of different percentages in terms of wear resistance, friction coefficient, hardness, and strength. The wear resistance was assessed using the specific wear work parameter determined by the novel tribotester with friction band. It was found that an increase in quartz powder addition to the tested polymer composite does not enhance its mechanical increasingly properties. From the wear tests it can be concluded that only the composite with four layers of glass fibers and 6 wt.% of the quartz powder exhibited improvement of the wear resistance, but its shear strength was lower than that of the two layer specimens with similar powder proportions. On the other hand, the highest friction coefficient's, which is microhardness HV 05 , shear strength and impact strength were attained for the composite with two layers of glass fibers and 3 wt.% of the quartz powder. Among four layer samples, very close results were obtained for the samples with 10% of powder and insignificantly lower strength were observed for the samples with no powder added. The results revealed that there is no clear trend for the effect of silica filler percentage on the composite performance, which indicates the need for individual purpose-dependent decision making in the design of the glass fiber reinforced composites with quartz powder filler.

The paper presents results of investigations on the binderless nanostructured tungsten carbide (WC) cutting tools fabrication and performance. The scientific novelty includes the description of some regularities of the powder consolidation under electric current and the subsequent possibility to utilize them for practical use in the fabrication of cutting tools. The sintering process of WC nanopowder was performed with the electroconsolidation method, which is a modification of spark plasma sintering (SPS). Its advantages include low temperatures and short sintering time which allows retaining nanosize grains of ca. 70 nm, close to the original particle size of the starting powder. In respect to the application of the cutting tools, pure WC nanostructure resulted in a smaller cutting edge radius providing a higher quality of TiC/Fe machined surface. In the range of cutting speeds, v c = 15-40 m/min the durability of the inserts was 75% of that achieved by cubic boron nitride ones, and more than two times better than that of WC-Co cutting tools. In additional tests of machining 13CrMo4 material at an elevated cutting speed of v c = 100 m/min, binderless nWC inserts worked almost three times longer than WC-Co composites.

In the paper, a novel technique for highly dispersed pyrochlore Y 2 Ti 2 O 7 is proposed. The experimental results proved that the application of microwave irradiation at a certain stage of calcination allowed synthesizing of Y 2 Ti 2 O 7 in much shorter time, which ensured substantial energy savings. An increase up to 98 wt.% in the content of the preferred phase with a pyrochlore-type structure Y 2 Ti 2 O 7 was obtained after 25 h of yttrium and titanium oxides calcination at a relatively low temperature of 1150 °C, while the microwave-supported process took only 9 h and provided 99 wt.% of pyrochlore. The proposed technology is suitable for industrial applications, enabling the fabrication of large industrial amounts of pyrochlore without solvent chemistry and high-energy mills. It reduced the cost of both equipment and energy and made the process more environmentally friendly. The particle size and morphology did not change significantly; therefore, the microwave-assisted method can fully replace the traditional one.

In this study, the effect of the addition of silicon carbide to alumina ceramics commonly used in cutting tool applications is addressed. Performance of Al 2 O 3 -SiC composite cutting inserts during the machining of hardened steels and ductile iron was compared to the results obtained for a cutting tool made out of 99 wt.% Al 2 O 3 , Al 2 O 3 -TiC, Al 2 O 3 -TiC-ZrO 2 , and Al 2 O 3 -TiN. In almost all tests, the composite with silicon carbide demonstrated better wear resistance, longer tool lifetime, and the ability to cut at higher speeds. The enhanced properties of cutting tools with SiC can be attributed to the morphology and dimensions of the inclusions in the matrix as well as to the strength of the interphase boundaries, small porosity, and lack of high inner stresses in the volume.

In the paper, the results of experimental investigations of ion implanted cutting tools performance are presented. The tools, made out of Si 3 N 4 with additives typically used for turning of Ti-6Al-4V alloy, underwent implantation with ions of yttrium (Y + ) and rhenium (Re + ) using the metal vapor vacuum arc method. Distribution of ions on the tool surface was measured. The cutting tools were tested in turning process with measurement of cutting forces and analysis of wear. A rather unexpected result was the increased wear of the tool after Y + implantation with 1 × 10 17 ion/cm 2 . It was demonstrated, however, that the tool after Y + 2 × 10 17 ion/cm 2 ion implantation provided the best machining performance.