Evgeny Grigoryev

Spark-plasma sintering (SPS) of composite ceramics in the β-Si5AlON7– system (SiC, TiN, BN) was studied. An effective mechanism of intensification of sintering processes was revealed due to the introduction of h-BN, having a scaly structure and playing the role of a solid lubricant, which improves the compressibility of the sintered powder mixtures under load. For composites containing 0–30 wt. % h-BN, 0–40 wt.% β-SiC, and 0–40 wt. % TiN, with different character distribution of components by volume (homogeneous, layered and gradient), the optimal parameters of the PCA were established, ensuring the achievement of a high level of relative density (not less than 95%) and functional characteristics. According to XRD results, the raw powders of β-Si5AlON7, h-BN, and TiN did not contain impurity phases while β-SiC had trace amounts of Si3N4. According to SEM results, all as-synthesized powders appeared largely as agglomerates. Their specific surface was about 1.3 m2/g for β-Si5AlON7 pow...

The main features of high-voltage electropulse consolidation (H-VEC) of powder materials and the unique possibilities of the method caused by them are considered. The electro-thermal processes in the H-VEC at the contacts between the powder particles and in the macroscale of the whole consolidated sample are analyzed. The results of calculations of the dynamics of closure (collapse) of interparticle pores in the consolidated material are presented. The experimental results of high voltage consolidation W-based heavy alloys are discussed and a theoretical analysis of the kinetics of compaction of powder materials is made. The results of investigation of the macroand microstructure of consolidated materials and the stress strain testing are presented. Compression testing showed that all tested alloys bear compressive stress at room temperature without failure. Figure 1 shows a characteristic diagram of the compressive deformation, which indicates the appearance and development of plas...

ABSTRACT Fe, Ti powders, and their mixtures were subjected to electric discharges in a hydrocarbon liquid. During this treatment, the powder particles’ refinement and carbide phase formation occurred. The obtained powder mixtures were consolidated by spark plasma sintering at 900 °C for 5 min under uniaxial pressure of 50–60 MPa. The densification behavior, microstructure, phase composition, and mechanical properties of the processed powder samples were investigated. The obtained results indicate the final structure sensitivity to the powder chemical composition and to the regimes of the powder synthesis by the electric discharges. The developed fabrication approach represents a novel technological route for metal–ceramic powder composites’ fabrication where the electromagnetic field assistance is employed at both powder synthesis and powder consolidation stages.

—In the present work, the properties of Al 2 O 3 nanocomposite prepared via spark-plasma sintering and reinforced with 0.5–2 wt % graphene are studied. Samples with different graphene contents are subjected to measurements of density, microhardness, coefficient of friction of composite–ruby, and frictional wear rate of composite. The fracture and wear track surface are inspected via fractography, and the composite as a whole is examined via X-ray diffraction. The graphene additive is established to increase the microhardness and to decrease the frictional wear rate by two orders of magnitude on account of absence of flaking of grains.