Igor S. Batraev

Detonation Spraying of Ti–Al Intermetallics: Phase and Microstructure Development of the Coatings

The goal of this work was to study the phase and microstructure changes involved in the process of coating formation by detonation spraying of Ti3Al, TiAl, and TiAl3 intermetallics. The O2/C2H2 ratio was varied between 1.1 and 2.0, and the explosive charge was 30–40% of the barrel volume. In most experiments air was used as a carrier gas; selected experiments were performed with argon. We found that depending on the spraying parameters, TiAl3 essentially retains in the coatings or partially decomposes forming TiAl and Ti3Al as minor phases. Detonation sprayed Ti3Al reacts with nitrogen and oxygen partially transforming into titanium nitrides TiN/Ti2N and titanium oxynitrides TiNxOy. TiAl partially decomposes forming Ti3Al, which further reacts with oxygen and nitrogen as the particle temperature and the content of oxygen in the explosive mixture increase. The in situ formed titanium nitrides and oxynitrides show a reinforcing effect increasing the hardness of the coatings.

Effect of the microstructure of SHS powders of titanium carbide–nichrome on the properties of detonation coatings

Experiments are carried out for the self-propagating high-temperature synthesis of TiC–NiCr cermets, implemented in a mechanically activated powder mixture of Ti–C–NiCr in the free combustion mode and under pressure. It is found that an increase in the volume fraction of the binder decreases the size of TiC inclusions in particles obtained by the mechanical grinding of synthesized cermet compacts. A CCDS2000 computerized facility developed at the Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, is used to sputter the coatings. The results of comparison of the characteristics of detonation coatings made from the powders produced in this work and commercial Cr3C2–NiCr powder are given. The prospects of employing the self-propagating high-temperature synthesis of TiC–NiCr powders for the thermal spraying of wear resistant coatings are discussed.

Control of interfacial interaction during detonation spraying of Ti 3 SiC 2 -Cu composites

Changes in the phase composition of the 20 vol % Ti3SiC2-Cu composite during detonation spraying as well as corresponding microstructure formation processes in the sprayed coatings have been studied. It was demonstrated that when the amount of the explosive acetylene+oxygen mixture is kept constant (under the constant filled volume fraction of the barrel of the detonation gun of a CCDS2000 facility), the phase composition of the coating depends on the composition of the explosive mixture. The Ti3SiC2-Cu system is prone to interfacial interaction; therefore, in order to produce a dense coating preserving the phase composition, oxygen-depleted explosive mixtures should be used and small filled fractions of the barrel. As the temperature of the sprayed particles increases with increasing oxygen content in the explosive mixture, titanium silicon carbide reacts with copper, which results in the formation of the titanium carbide phase and dissolution of the de-intercalated silicon in the copper matrix leading to the formation of TiCx-Cu〈Si〉 coatings.

Diagnostics of the structure and composition of ultrafine carbon obtained by detonation

A complex of methods is employed to study the properties of carbon condensate obtained by detonation of the enriched acetylene/oxygen mixture. The effect of the gas mixture composition and the methods to initiate detonation, which provide the preparation of ultrafine products, are analyzed. According to the powder X-ray diffraction and electron microscopy data, the detonation products are a carbon condensate consisting of coalescent amorphous particles with a size of ∼100 nm.

In situ formation of metal-ceramic composite coatings by detonation spraying of titanium

We have studied the phase formation and concomitant microstructure evolution in the coatings deposited by detonation spraying of a titanium powder. By varying the O2/C2H2 ratio, detonation products of different compositions were produced, which determined the course of the phase evolution. The carrier gas also played an important role in the phase formation of the coatings. It was found that the phase composition of the coatings forms as a result of nitridation, oxidation and carbon capture depending on the O2/C2H2 ratio and the nature of the carrier gas. The in situ formed metal-ceramic coatings possess unique microstructures and present interesting objects for studying their mechanical behavior. Detonation spraying of titanium can be suggested as a convenient way of forming metal-ceramic coatings with a controlled phase composition resulting from the reactions of titanium with the spraying environment of variable chemistry.

Microstructure and Wear Resistance of Detonation Coatings Obtained from Titanium Carbide–Nichrome SHS Powders Having Different Particle Sizes

The size effect of particles (20–45, 45–56, 56–71, 71–90 μm) of TiC–NiCr n vol % (n = 30, 40, 50) self-propagating high-temperature synthesis (SHS) cermet powders synthesized in the direct combustion mode on the tribological characteristics of detonation coatings is studied. These powders are sprayed in a mode optimized previously using Cr3C2–NiCr 21 vol % commercial cermet powder (PraxAir 1375VM, USA) with particle sizes ranging from 20 to 45 μm.

Generation of Hypervelocity Particle Flows by Explosive Compression of Ceramic Tubes

The compression of ceramic (corundum) tubes by the detonation products of explosives have been studied experimentally and numerically. The formation of the shaped-charge jet of ceramic particles and its effect on steel witnesses targets has been investigated. The tubes were produced by detonation spraying. Ceramic particles were deposited on copper tubes, which were then dissolved in a solution of ferric chloride. In the experiments, a considerable penetration of the flow of ceramic particles was observed. During the interaction of the flow with the target, the target material was partially evaporated, as shown by metallographic analysis. Numerical analysis of the formation of the discrete shaped-charge jet showed that the maximum velocity of the jet head was about 23 km/s, and the velocity of the main part of the jet was about 14 km/s.

Investigation of Gas Detonation in Over-Rich Mixtures of Hydrocarbons with Oxygen

Detonation in mixtures of acetylene, ethylene, and propylene with oxygen in the range of fuel component concentrations with possible formation of carbon condensate in detonation products is studied both experimentally and theoretically. In contrast to the traditional method of studying detonation in a quiescent mixture located in a closed tube, the present investigations are performed in a tube with an open end (for exhaustion of detonation products) under the conditions of separate injection of the components and their mixing after injection into the detonation tube through the ignition chamber. The components are injected into the tube from a computercontrolled multichannel system of gas injection of the CCDS2000 detonation spraying setup. The detonation cell size and detonation velocity are measured; these parameters are also calculated by the BEZOPASNOST (SAFETY) computer program. A comparison of the computed and experimental dependences testifies to a complicated character of transformation of detonation products from a purely gaseous to heterogeneous state and to its effect on the detonation wave.

Structural and mechanical characterization of detonation coatings formed by reaction products of titanium with components of the spraying atmosphere

Structural characterization of detonation deposits formed by reaction products of titanium with the components of the spraying atmosphere showed that ceramic-based coatings of unique microstructures—consisting of alternating layers of different compositions—can be formed. For the first time, mechanical characteristics of the coatings formed by reaction-accompanied detonation spraying of titanium were evaluated. It was found that high-yield transformation of titanium into oxides and nitrides during spraying can result in the formation of coatings with high fracture resistance and interface fracture toughness. The hardness of the coatings measured along the cross-section of the specimens was higher than that on the surface of the coatings, which indicated mechanical anisotropy of the deposited material. In terms of mechanical properties, coatings formed by the reaction products appear to be more attractive than those specially treated to preserve metallic titanium.

Detonation of a gas fuel based on methyl acetylene and allene

A special facility for investigating gaseous detonation was designed using a CCDS2000 computerized detonation-spraying complex to implement flow-through supply of the components of an explosive mixture and activation of deflagration-to-detonation transition in a long cylindrical channel. The detonation velocity and the cell size of the detonation front in mixtures of a composite fuel based on methyl acetylene and allene with oxygen were experimentally determined, and the concentration limits of steady-state detonation in a tube of 26 mm diameter were obtained. Detonation parameters were calculated and compared with experimental values. For comparison, the detonation of mixtures of acetylene and propane-butane with oxygen under similar conditions was studied.