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WC-(Fe-Mn-C) composites with γ-iron and γ + α’ matrices were sintered and then tested at sliding speeds in the range 7–37 m/s. The coefficient of friction was exponentially reduced as a function of sliding speed reaching its minimum at 37 m/s. This behavior was provided by the mechanochemical formation of iron tungstate FeWO4 on the worn surfaces of composite samples. The lubricating effect of iron tungstate did not, however, allow for a reduction in wear. The worn surface was represented by a 3–10 μm-thickness tribological layer composed of fine WC and iron particles cemented by FeWO4. This layer provided the self-lubricating effect in high-speed (high-temperature) sliding because of its easy shear and quasi-viscous behavior. The underlying 25–65 μm of thickness layer was composed of only heat-affected WC and recrystallized iron grains.

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Abstract. This work investigates the behavior of porous alumina (with the porosity ranging from 18% to 70%) and zirconia (with the porosity ranging from 10% to 60%) ceramics when subjected to deformation by compression and shearing. The analysis of stress-strain curves showed that there is a transition from a typical brittle state for relatively dense ceramics, to a pseudo-plastic one for ceramics with high porosity. The values of the effective Young's modulus, effective shear modulus and Poisson's ratio decrease with the increase of the pore space volume of ceramics, which correlates with the appearance of multiple cracking during the deformation of the high porosity ceramics.

this work investigates the behavior of porous alumina ceramics (within the porosity range of 18% to 70%) when subjected to deformation by compression and shear. the analysis of straindeformation curves showed that there was a transition from a typically brittle state for relatively dense ceramics (≤20% porosity), to a pseudo-plastic one with a high rate of porosity (above 50%). the values of the modulus of elasticity, shear modulus and Poisson's ratio decrease with an increase in volume in the pore space of Al 2 o 3 ceramics, which correlates with the appearance of multiple cracking during the deformation of ceramics with a high level of porosity.

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The behavior of alumina and zirconia compression-and shear-test specimens with porosity ranging from 10 to 70% is investigated. Analysis of the stress-strain curves for the materials under study has revealed a transition from a characteristically brittle fracture of fairly dense Al 2 O 3 and ZrO 2 specimens to pseudo-plastic fracture for a high porosity level. The ultimate compression strength, effective elastic and shear moduli, and Poisson's ratio are found to decrease with increase in the pore space volume of the ceramic specimens, which is shown to correlate with development of strain-induced multiple cracking of the materials.

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