M. Prozorova

Structure and properties of an Al2O3 powder coating formed by a cumulative detonation method

The strength of the Al2O3 powder coating formed by a cumulative detonation method on a steel St3 substrate is determined, and its structure is studied. The optimum conditions for deposition are chosen. They make it possible to form a dense high-strength coating with good adhesion to the substrate.

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF ALUMINA POWDER COATINGS BY A NEW MULTI-CHAMBER DETONATION SPRAYER

The dense ceramic coatings based on alumina with hardness of 1100±25 HV0.3 and porosity of less than 1% have been prepared by multi-chamber detonation sprayer (MCDS) with a barrel length of 500mm. The intermetallic compound of type FeAl was revealed in the area of the coating that adjoins the substrate.

Synthesis of Magnesium Oxide Nanopowder by Thermal Plasma Using Magnesium Nitrate Hexahydrate

Magnesium oxide (MgO) nanopowder was synthesized by thermal plasma in a novel thermal DC plasma torch using magnesium nitrate hexahydrate. Magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) was obtained from serpentinite (Mg3Si2O5(OH)4; lizardite) (Halilovskiy array, Orenburg region, Russia). The synthesized samples were characterized by analytical techniques including X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD and TEM characterization studies confirmed that MgO nanopowder obtained has periclase structure with high purity, and the particle sizes vary within the range of 100 nm to 150 nm. We believe that the present work will promote further experimental studies on the physical properties and the applications of MgO nanopowders in the fields such as high-densed ceramics, additives in bactericide, and refractory products.

Properties of Alumina-Titania Coating Formed by a New Multi-Chamber Gas-Dynamic Accelerator

Thermal-sprayed alumina–titania coatings (Al2O3:Ti wt ratio = 60:40) were prepared by a new multi-chamber gas-dynamic accelerator. The coatings were examined by using scanning electron microscopy, X-ray phase analysis and Vickers hardness tester at a test load 0.2 kg. The coating was well-adhered with corrosion-resistant steel substrate. The results show that the microstructure of the alumina–titania coatings consists of areas with different degrees of melting: the lamella built up from the fully melted particles of the powder, and partially melted areas. The developed coating is highly dense (porosity is less than 0.7%). Research results show that hardness of alumina–titania coatings (Al2O3:Ti wt ratio = 60:40) can achieve up to 655 HV0.2 and the specific wear rate of alumina-titania coatings is 52.40∙10-5 mm3 (m∙N)-1.

Structure and Microhardness of Titanium-Based Coatings Formed by Multichamber Detonation Sprayer

A series of titanium-based coatings (50–550 μm thick) on an aluminium substrate was deposited via multichamber detonation sprayer with different barrel lengths (300, 400, and 500, all in mm). The titanium-based coatings obtained in these three experiments were examined by optical microscopy, scanning electron microscopy, and X-ray phase analysis. The hardness tests were carried out by the Vickers method with a test load of 50 g. The multichamber detonation sprayer with a barrel length of 500 mm produced the dense layers of coating with hardness of  HV0.05 and porosity of 0.24%, the best result in the experiments.

Properties of Powder Coatings Formed by Gas-Dynamic Accelerator

Abstract The paper presents the results of investigating the properties of metal and ceramic coatings deposited on the steel or the aluminium substrates by using a multi-chamber gas-dynamic accelerator. The multi-chamber gas-dynamic accelerator (MCDS) has replaceable nozzles and operates with a fuel mixture of low-pressure gases – propane (30 %) + butane (70 %) – oxygen – air. The velocity of the frontal area of the cloud of the Al 2 O 3 powder with particle sizes of 5.6 – 22.5 μm at a nozzle length of 500 mm is 1300 ± 200 m/s. MCDS with a nozzle length of 500 mm provides the conditions for formation of a dense ceramic layer having hardness of 1320 ± 25 HV 0.3 and porosity of less than 1 %. Productivity of the technology is 0.72 kg/h at a deposition efficiency - 65 %, flow rate of oxygen equal to 7.7 m 3 /h, and flow rate of propane + butane equal to 1.3 m 3 /h. High adhesion of the ceramic layer to the substrate is provided by the transition layer up to 15 μm thick. MCDS allows form Nano-crystalline coating of the titanium or nickel based alloy powders. The dense layer of lamellas and deformed particles of powder is formed on the sample surface. Lamellas consist of Nano-crystalline grains size of 30 – 100 nm. Scratch-test has shown that the coatings are plastic and have high adhesive and cohesive strength.

Tribological characteristics of nanosized carbon coatings obtained by the pulsed vacuum-arc method on the modified TiNi surface

Tribological tests of nanosized carbon coatings produced by the pulsed vacuum-arc method on the surface of NiTi premodified by ions of nitrogen and titanium are conducted. The surface modification and formation of a carbon coating 180 nm thick on the surface of a softer material, titanium nickelide, is shown to considerably increase wear resistance and reduce the coefficient of friction.