Yu. Tyurin

Electric heating using a liquid electrode

Abstract This work deals with analysis of the processes occurring in the electrolyte and in the plasma layer formed between the liquid electrode-anode and the solid workpiece surface. The electrolyte-plasma quenching method, in which the formation and stabilization of the plasma layer are supported by periodical increase and decrease of the electric voltage was utilized. Changing of switching on time of an increased electric potential and varying its value, we could control the heating and cooling rates of the workpiece surface within 20–500°C/s. This allowed us to form the quenched layers, with thickness from 1 to 10 mm. The possibility of controlling the rate of this periodical heating and cooling allowed us to realize the thermo-cycling treatment of surfaces. Applications of electrolyte plasma quenching include: inner cylindrical surfaces; workpieces, e.g. rolls, knives, saws in metallurgy, metal mining industry and agriculture.

Surface Modification of Iron Carbon Alloys by Plasma Detonation Treatment

Abstract Plasma detonation method (PDM) is based on the use of pulse plasma jets formed by transformation of a detonation wave into a plasma pulse. Energy density in such a jet amounts to 107 W cm−2, Consumable electrodes used here allow the vapors of various metals to be introduced into the jet. PDM is applied for heat treatment of surfaces, their alloying, as well as for coating deposition. The process of surface modification of carbon steels using various electrodes is investigated. The effect of the treatment conditions and the electrode materials on surface hardening is discussed.

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.

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.