Virial Ltd

Saint Petersburg, Russia

Virial Ltd

Saint Petersburg, Russia
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Chuvil'deev V.N.,Novgorod State University | Boldin M.S.,Novgorod State University | Dyatlova Ya.G.,VIRIAL Ltd. | Rumyantsev V.I.,VIRIAL Ltd. | Ordanyan S.S.,Saint Petersburg State University
Inorganic Materials | Year: 2015

We have studied the sintering kinetics of Al2O3-ZrO2-Ti(C,N) powders during hot pressing and spark plasma sintering. The results demonstrate that, at slow heating rates and under identical hot pressing and spark plasma sintering conditions, the consolidation processes have identical kinetics in the active densification stage and are characterized by identical activation energies. © 2015 Pleiades Publishing, Ltd.

Rumyantsev V.,VIRIAL Ltd. | Kovelenov N.,VIRIAL Ltd. | Korableva N.,VIRIAL Ltd. | Bulatov O.,VIRIAL Ltd. | Ordanyan S.,Saint Petersburg State University
Proceedings of the Euro International Powder Metallurgy Congress and Exhibition, Euro PM 2011 | Year: 2011

The plasma chemical TiN-TiB2 powders and mechanically activated equiweight mixture of submicron TiN-TiB2 powders were consolidated by hot pressing and spark plasma sintering in N2 atmosphere. Samples based on mechanically activated equiweight mixture of submicron TiN-TiB2 powders showed optimal physical and mechanical parameters when consolidated by hot pressing at 1770°S (bending strength 500 MPa, Vickers' hardness 22 GPa, fracture toughness (K1S) 5 MPa·m1/2), while samples based on plasma chemical powders achieved maximum parameters when processed by spark plasma sintering at 1400°S (bending strength 390 MPa, Vickers' hardness 18. 7 GPa, fracture toughness (K1S) 6 MPa·m1/2). Cutting insert samples based on hot-pressed activated equiweight mixture of submicron TiN-TiB2 powders demonstrated acceptable results in turning tests performed on cast iron workpieces.

Rumyantsev V.,VIRIAL Ltd | Osmakov A.,VIRIAL Ltd | Korableva N.,VIRIAL Ltd | Belykh N.,VIRIAL Ltd | And 4 more authors.
Proceedings of the World Powder Metallurgy Congress and Exhibition, World PM 2010 | Year: 2010

Dense ceramics based on nanosized composite plasma chemical powders Si3N4 (30-100 nm) was obtained by activated pressureless sintering (PS), hot pressing (HP), hot isostatic pressing (HIP) and spark plasma sintering (SPS). XRD analysis showed the obtained ceramics to contain predominantly β-Si3N4 and cubic YAG-type phase. Microstructure characterization by light and scanning electron microscopy showed the smoothing of grain outlines after PS. Such texture effects are supposedly related to prolonged dwell time during heat treatment that leads to greater amount of liquid phase in the material. In SPS-ed samples the smoothed grain outlines might be related to the considerable overheating caused by specific process features. Physical and mechanical performance of the samples is compared. The HP-ed samples showed optimal hardness/fracture toughness ratio. Relative density of ceramics is over 0. 99, flexural strength is over 800 MPa, Vickers' hardness is 17-18 GPa, fracture toughness ratio is 7. 5 to 8. 5 MPa·m1/2. The obtained samples were characterized for cutting performance, as compared to existing commercial cutting inserts based on silicon nitride. The highest wear resistance values were demonstrated by hot-pressed insert samples.

Fedorov D.,VIRIAL Ltd. | Rumyantsev V.,VIRIAL Ltd. | Radtsig N.,VIRIAL Ltd. | Osmakov A.,VIRIAL Ltd. | And 2 more authors.
Proceedings of the World Powder Metallurgy Congress and Exhibition, World PM 2010 | Year: 2010

Following the general trend of development of cutting tool materials with improved wearresistance the new composite materials based on conventional cemented carbide grade VK6 were developed, using disperse cubic BN as reinforcement and pulsed current sintering technique. Fully dense composite material samples were developed by high-speed hot pressing (HSHP) and spark plasma sintering (SPS) at 1120-1280°C and pressure of 100 to 200 MPa. Microstructures and mechanical performance of these materials were compared to similar samples consolidated by high pressure - high temperature techniques (HPHT) and to conventional WC-Co cemented carbide with similar Co binder contents. New materials demonstrated over 30% improvement in hardness and fracture toughness.

Dyatlova Y.G.,Virial Ltd | Agafonov S.V.,Virial Ltd | Boikov S.Y.,Virial Ltd | Ordanyan S.S.,Saint Petersburg State Polytechnic University | Rumyantsev V.I.,Virial Ltd
Powder Metallurgy and Metal Ceramics | Year: 2011

Oxide composite Al 2O 3-ZrO 2(Y 2O 3) powders containing 50 and 70 vol.% Al 2O 3, are deposited from salt solutions. The surface area of the deposited powders exceeds 75 m 2/g. It is established that the α-Al 2O 3 and t-ZrO 2(Y 2O 3) matrix has an effect on stepwise crystallization of α-Al 2O 3 and the powder production history on the sinterability of oxide composites. Ceramics based on Al 2O 3-ZrO 2(Y 2O 3) composite powder containing 20 vol.% titanium carbonitride are hot pressed to be used as a cutting tool. The microstructure and mechanical properties of the ceramics are analyzed. The best mechanical properties are shown by ceramic samples sintered at 1550°C at 35 MPa: bending strength 950 MPa, fracture toughness 10.1 MPa . m 1/2, and hardness 18.0 GPa. The performance and lifetime of cutting tools based on these ceramics are tested according to GOST 26613-85. © 2011 Springer Science+Business Media, Inc.

Pesin V.,VIRIAL Ltd. | Rybin D.,VIRIAL Ltd. | Dyatlova Y.,VIRIAL Ltd. | Osmakov A.,VIRIAL Ltd.
Technical Physics Letters | Year: 2012

Samples of yttria-stabilized zirconia (YSZ) and magnesia-stabilized zirconia (MSZ) ceramics were analyzed by grazing angle XRD technique in order to gain insights into the effects of the autoclave treatment (140°, 207 kPa, 15 h) on transformation of tetragonal ZrO 2 into monoclinic zirconia (known as low-temperature degradation, LTD). Models were developed to describe the distribution of m-ZrO 2 across the depth of the degraded layer. Based on the results of the study it was established that the m-ZrO 2 contents in the polished YSZ surfaces after the autoclave treatment was changed by 48%, whereas those of MSZ-only by 4%. Moreover, the hydrothermal modification process is confined to the thin near-surface layer. This layer had thickness corresponding approximately to one average grain size. It was shown that the grazing angle XRD technique was the only method capable of adequate characterization of the degraded layer thickness and overall LTD effect parameters. © 2012 Pleiades Publishing, Ltd.

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