scholarly journals The Effect of Increasing the Air Flow Pressure on the Properties of Coatings During the Arc Spraying of Cored Wires

2019 ◽  
Vol 69 (4) ◽  
pp. 133-146 ◽  
Author(s):  
Student Mykhailo ◽  
Gvozdetsky Volodymyr ◽  
Student Oleksandra ◽  
Prentkovskis Olegas ◽  
Maruschak Pavlo ◽  
...  
Keyword(s):  
High Speed ◽  
Substrate Surface ◽  
Air Flow ◽  
Oxide Phase ◽  
Arc Spraying ◽  
Properties Of Coatings ◽  
Structure Of Coatings ◽  
Flow Pressure ◽  
Cored Wires ◽  
Metal Droplets

AbstractThe melting conditions of the electrode wires and the structure of coatings, obtained by the electric arc spraying method depending on the pressure of the spraying air flow, are analysed in the current paper. The effect of air pressure on the spraying angle of the flow of melted metal droplets is demonstrated. It is established that due to the decrease in this spraying angle, the temperature of the droplets increases. In addition, high-speed airflow is more easily captured by smaller molten metal droplets and during the contact with the substrate surface their deformations were more strongly. Due to such phenomenon, the porosity of the coatings was reduced and the number of lamellae, welded to each other, increased. With the increasing pressure of the air flow, the thicknesses of the lamellae were decreased, however, the amount of the oxide phase in the coatings has increased. As a result, the hardness, wear resistance and cohesive strength of the coatings, obtained at a higher pressure of the air flow, have increased, and the level of residual stresses of the first kind in them decreased.

Spraying Coatings by Supersonic Metallization

2000 ◽  
Author(s):  
I. Karp ◽  
A. Rudoy
Keyword(s):  
High Speed ◽  
Protective Coatings ◽  
Combustion Products ◽  
Arc Spraying ◽  
Supersonic Stream ◽  
Properties Of Coatings ◽  
Equipment Complex ◽  
Motor Component ◽  
Specialized Equipment ◽  
Hydrocarbon Gas

Abstract A technology and a specialized equipment complex based on supersonic arc spraying gun, where a supersonic stream of combustion products of hydrocarbon-gas (HC-gas) with air is used as an atomizing gas, have been developed. Durable and safe work of coated parts functioning under conditions of intensive loading is determined (except general requirement to coatings: wear resistance, hardness) to a large extent by the fatigue strength, porosity and stability of the properties of coatings. New possibilities for satisfying all the requirement to coatings on parts type are opened up by a high speed spraying of wire. This is provided at the expanse of raising the kinetic energy of particles under spray, increase of their concentration in metal stream, lowering of the spread of parameters in the vicinity of a substrate. This, in its turn, determines the increase of adhesive and cohesive strength of coating, the decrease of oxidation, the improvement of stability and reproducibility of its properties. The results of the investigations of the influence of the variable parameters of the process on the listed above properties of coatings are presented. This technology and equipment complex is appreciated for repair of wearied motor component and deposition of corrosion protective coatings.

scholarly journals Influence of Diameter of Electrode Powder-like Wires is on Mechanical Descriptions of Elektrodugovikh Coverages

2020 ◽  
pp. 32-42
Author(s):  
Mykhajlo Student ◽  
◽  
Myroslav Golovchuk ◽  
Halyna Chumalo ◽  
Volodymyr Hvozdetskii ◽  
...  
Keyword(s):  
Wear Resistance ◽  
Abrasive Wear ◽  
Oxide Phase ◽  
Electric Arc ◽  
Abrasive Wear Resistance ◽  
Tensile Stresses ◽  
Air Jet ◽  
Steel Base ◽  
Structure Of Coatings ◽  
Cored Wires

The influence of the diameter of the electrode flux-cored wires on the mechanical characteristics of the electric arc coatings is carried out in the work. Electric arc coatings were obtained on the original equipment, developed and manufactured at the Institute of Physics and Mechanics. GV Karpenko NAS of Ukraine. For spraying, model flux-cored wires of basic doping systems Fe – Cr – C and Fe – Cr – B with a diameter of 1.6 and 2.4 mm were used. The influence of the diameter of flux - cored wires on the structure, electric arc coatings from model flux - cored wires of different diameters is investigated. The dependence of porosity, microhardness, adhesion to the steel base, abrasive wear resistance of electric arc coatings sprayed from flux-cored wires with different amounts of charge on the thickness of the lamellae in the coating structure has been established. The influence of the thickness of the lamellae in the structure of coatings sprayed from flux-cored wires with different amounts of charge (depending on their diameter 1.6 and 2.4 mm) on their abrasive wear resistance was determined. It was found that the thickness of the lamellae in the coatings of all analyzed alloying systems increased with increasing volume of molten metal at the ends of flux-cored wires with the corresponding formation of droplets of larger diameter during its dispersion by air jet. shell charge and high arc current. It is shown that the amount of oxide phase in the structure of coatings doubles with increasing spray distance of flux-cored wires from 80 to 120 mm. More oxide phase (40… 100%) was found in coatings formed of flux-cored wires with a diameter of 2.4 mm with a higher filling factor of its shell charge compared to coatings formed of flux-cored wires with a diameter of 1.6 mm with lower filling. This is due to the larger volume of the charge in the powder wires of larger diameter, the cavities between the powders in which are filled with air, which intensively oxidizes the melt droplets inside the powder wires and at their ends during spraying. It is established that the porosity and microhardness of coatings from the developed flux-cored wires increase with the increase of the thickness of the lamellae in their structure and, accordingly, the diameter of the flux-cored wires. The increase in micro hardness is due to less evaporation and burnout of alloying elements from the droplets forming the coating, and the increase in porosity is caused by intensive spraying of droplets when hitting the sprayed surface, which contributes to micro cavities between the lamellae of the coating. It was found that with increasing the thickness of the lamellae in the structure of coatings of flux-cored wires 250H21VFGS and flux-cored wires 50HN2R5GS their adhesion to the steel base decreased slightly due to the occurrence of tensile stresses in coatings, which cause micro cracks or cracks. At the same time, the adhesion of 50X6MG2C flux-cored wire coatings to steel increased due to the higher carbon content of large lamellae and favorable conditions for the formation of high-carbon martensite, which has the lowest coefficient of thermal expansion and causes the lowest residual tensile stresses. It was found that the abrasive and gas-abrasive wear resistance of coatings from flux-cored wires 250Х21ВФГС decreased, and from flux-cored wires 50ХН2Р5ГС increased due to the increase in the thickness of the lamellae in their structure using a larger diameter.

MULTIDIMENSIONAL SIMULATIONS AND TEST FIRES OF A HYDROGEN-FUELED RAMJET WITH AN ANNULAR DETONATIVE COMBUSTOR AT APPROACHING AIR FLOW OF MACH 2 AND 1.5

2020 ◽  
Author(s):  
V. S. IVANOV ◽  
◽  
V. S. AKSENOV ◽  
S. M. FROLOV ◽  
P. A. GUSEV ◽  
...  
Keyword(s):  
Unmanned Aerial Vehicles ◽  
High Speed ◽  
Constant Pressure ◽  
Air Flow ◽  
Thermodynamic Cycle ◽  
Aerial Vehicles ◽  
Mach Numbers

Modern high-speed unmanned aerial vehicles are powered with small-size turbojets or ramjets. Existing ramjets operating on the thermodynamic cycle with de§agrative combustion of fuel at constant pressure are efficient at flight Mach numbers M ranging from about 2 to 6.

Influence of Process Parameters and Geometry of the Spraying Nozzle on the Properties of Titanium Deposits Obtained in Wire Arc Spraying

2015 ◽  
Vol 1111 ◽  
pp. 211-216
Author(s):  
Bogdan Florin Toma ◽  
Iulian Ionita ◽  
Diana Antonia Gheorghiu ◽  
Lucian Eva ◽  
Costică Bejinariu ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Process Parameters ◽  
High Speed ◽  
Electrical Current ◽  
Electric Arc ◽  
Arc Spraying ◽  
Oxide Content ◽  
Spray Parameters ◽  
Influence Of Process Parameters ◽  
Wire Arc Spraying

Influence of the process parameters and geometry of the spraying nozzle on the properties of titanium deposits obtained in wire arc spraying. Wire arc spraying is a process in which through minor modifications of the spray parameters, they can have a major impact on the coatings properties. In this paper there is presented a study on the influence of process parameters and fluid dynamics of the atomization gas on the properties of titanium deposits (14T - 99.9% Ti). For this there were used three different frontal spraying nozzles, having different geometries, and were varied the spraying gas pressure and the electrical current on three levels. There were evaluated the particles velocity, coating density, chemical composition and characteristic interface between deposition and substrate. Obviously, the high speed of the atomization gas determinate the improving of all properties, but in the same time increased the oxide content in the layer. However, the oxidation can be drastically reduced if the melting and atomization of the wire droplets is produced at the point of formation of the electric arc, and the spraying jet is designed to constrain the electric arc. The assessment of deposits adherence allowed the observation of process parameters that contribute to its improvement.

scholarly journals Structure and Properties of Coatings Made with Self Shielded Cored Wire

2016 ◽  
Vol 16 (3) ◽  
pp. 39-42 ◽  
Author(s):  
M. Gucwa ◽  
J. Winczek ◽  
R. Bęczkowski ◽  
M. Dośpiał
Keyword(s):  
Heat Input ◽  
Mining Industry ◽  
High Hardness ◽  
Properties Of Coatings ◽  
Cored Wire ◽  
Eutectic Carbides ◽  
Hard Particles ◽  
Wear And Corrosion ◽  
Flux Cored Arc Welding ◽  
Cored Wires

Abstract The welding technologies are widely used for design of protection layer against wear and corrosion. Hardfacing, which is destined for obtaining coatings with high hardness, takes special place in these technologies. One of the most effective way of hardfacing is using self shielded flux cored arc welding (FCAW-S). Chemical composition obtained in flux cored wire is much more rich in comparison to this obtained in solid wire. The filling in flux cored wires can be enriched for example with the mixture of hard particles or phases with specified ratio, which is not possible for solid wires. This is the reason why flux cored wires give various possibilities of application of this kind of filler material for improving surface in mining industry, processing of minerals, energetic etc. In the present paper the high chromium and niobium flux cored wire was used for hardfacing process with similar heat input. The work presents studies of microstructures of obtained coatings and hardness and geometric properties of them. The structural studies were made with using optical microscopy and X-ray diffraction that allowed for identification of carbides and other phases obtained in the structures of deposited materials. Investigated samples exhibit differences in coating structures made with the same heat input 4,08 kJ/mm. There are differences in size, shape and distribution of primary and eutectic carbides in structure. These differences cause significant changes in hardness of investigated coatings.

High Speed Imaging of Forced Ignition Kernels in Non-Uniform Jet Fuel/Air Mixtures

2017 ◽  
Author(s):  
Sheng Wei ◽  
Brandon Sforzo ◽  
Jerry Seitzman
Keyword(s):  
Heat Release ◽  
High Speed ◽  
Air Flow ◽  
Cetane Number ◽  
High Energy ◽  
Liquid Fuels ◽  
High Speed Imaging ◽  
Ignition Probability ◽  
Turbine Engine ◽  
Planar Laser

This paper describes experimental measurements of forced ignition of prevaporized liquid fuels in a well-controlled facility that incorporates non-uniform flow conditions similar to those of gas turbine engine combustors. The goal here is to elucidate the processes by which the initially unfueled kernel evolves into a self-sustained flame. Three fuels are examined: a conventional Jet-A and two synthesized fuels that are used to explore fuel composition effects. A commercial, high-energy recessed cavity discharge igniter located at the test section wall ejects kernels at 15 Hz into a preheated, striated crossflow. Next to the igniter wall is an unfueled air flow; above this is a premixed, prevaporized, fuel-air flow, with a matched velocity and an equivalence ratio near 0.75. The fuels are prevaporized in order to isolate chemical effects. Differences in early ignition kernel development are explored using three, synchronized, high-speed imaging diagnostics: schlieren, emission/chemiluminescence, and OH planar laser-induced fluorescence (PLIF). The schlieren images reveal rapid entrainment of crossflow fluid into the kernel. The PLIF and emission images suggest chemical reactions between the hot kernel and the entrained fuel-air mixture start within tens of microseconds after the kernel begins entraining fuel, with some heat release possibly occurring. Initially, dilution cooling of the kernel appears to outweigh whatever heat release occurs; so whether the kernel leads to successful ignition or not, the reaction rate and the spatial extent of the reacting region decrease significantly with time. During a successful ignition event, small regions of the reacting kernel survive this dilution and are able to transition into a self-sustained flame after ∼1–2 ms. The low aromatic/low cetane number fuel, which also has the lowest ignition probability, takes much longer for the reaction zone to grow after the initial decay. The high aromatic, more easily ignited fuel, shows the largest reaction region at early times.

The Impact of Oil and Sealing Air Flow, Chamber Pressure, Rotor Speed, and Axial Load on the Power Consumption in an Aeroengine Bearing Chamber

2005 ◽  
Vol 127 (1) ◽  
pp. 182-186 ◽  
Author(s):  
Michael Flouros
Keyword(s):  
Power Consumption ◽  
High Speed ◽  
Air Flow ◽  
Flow Chamber ◽  
Chamber Pressure ◽  
Power Losses ◽  
Rolling Element ◽  
Oil Flow ◽  
The Impact ◽  
Circle Diameter

Trends in aircraft engines have dictated high speed rolling element bearings up to 3 million DN or more with the consequence of having high amounts of heat rejection in the bearing chambers and high oil scavenge temperatures. A parametric study on the bearing power consumption has been performed with a 124 mm pitch circle diameter (PCD) ball bearing in a bearing chamber that has been adapted from the RB199 turbofan engine DN∼2×106. The operating parameters such as oil flow, oil temperature, sealing air flow, bearing chamber pressure, and shaft speed have been varied in order to assess the impact on the power consumption. This work is the first part of a survey aiming to reduce power losses in bearing chambers. In the first part, the parameters affecting the power losses are identified and evaluated.

scholarly journals Design and Fabrication of Two Step Speed Control of a Cylinder Circuit using Pneumatics

2019 ◽  
Vol 8 (6S2) ◽  
pp. 512-516
Keyword(s):  
Flow Control ◽  
High Speed ◽  
Air Flow ◽  
Control Valve ◽  
Speed Control ◽  
Flow Control Valve ◽  
Push Button ◽  
Low Speed ◽  
Flow Through

The main aim of our project is to design and fabrication of pneumatic two step speed control of a cylinder. Initially the flow from the FRL retracts the cylinder when the push button is in its spring offset position. When it is pushed the flow pilots actuate. The air passes through the flow control and shuttle valve. Then the cylinder extends with high speed as the valve allows more air to enter the cylinder. When the piston reaches the position it operates the cam push button and pilot air flow through this and actuate 5/2 pilot operated valve and reaches flow control valve which permits less air. Then the flow through enters the shuttle valve to cylinder and allows the cylinder to extend at relatively low speed. At the end of extension stroke deactivating push button retracts the cylinder. Thus the speed of cylinder is controlled and project can be achieved

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