scholarly journals Determination of adhesion of the coating deposited by arc spraying with pulsation of atomizing air flow

2021 ◽  
Vol 3 (12 (111)) ◽  
pp. 39-47
Author(s):  
Iryna Zakharova
Keyword(s):  
Adhesion Strength ◽  
Air Flow ◽  
Complex Loading ◽  
Test Methods ◽  
Aluminum Coating ◽  
Alloying Elements ◽  
Arc Spraying ◽  
Optimal Size ◽  
Pulsation Frequency ◽  
Conservation Of Energy

During electric arc spraying, during the transfer of molten metal by air flow, there is a significant burnout of alloying elements with the formation of a large amount of oxides, which negatively affects the adhesion of the coating to the base. A solution to the problem of increasing the adhesion strength by using pulsation of the atomizing air flow is proposed. At the optimal frequency of the pulsed flow shut-off, the time of formation of liquid metal droplets at the ends of the electrodes coincides with the frequency of pulses of the spraying flow. As a result, the droplets acquire an optimal size, they are transported by an air flow with conservation of energy, a lower mass of oxygen and, as a consequence, a significant decrease in the oxidation of alloying elements in the sprayed material. The existing test methods of sprayed coatings for adhesion strength to the base are analyzed. The design of a modernized device for determining the adhesion strength is developed and described, which provides complex loading of the coating with a combination of tear-off and shear. The tests revealed a significant (up to two times) increase in the adhesion strength of aluminum, zinc-aluminum and steel (Sv08A) coatings applied with air pulsation. This is achieved by increasing the number of fusion zones of the coating particles between themselves and with the base. It is shown that the effect of the pulsation frequency on the adhesion strength changes along a curve with a maximum corresponding to a frequency of 70–80 Hz, regardless of the coating material. It has been established that the aluminum coating has an increased tendency to oxidation, as a result of which it is 15–20 % inferior to the zinc-aluminum coating in adhesion strength. The data obtained substantiate the use of the proposed spraying technology in production

scholarly journals Use of pulsed spray airflow for electric arc spraying of different types of wires

2021 ◽  
Vol 3 (1(59)) ◽  
pp. 23-27
Author(s):  
Vyacheslav Royanov ◽  
Irina Zakharova
Keyword(s):  
Chemical Composition ◽  
Adhesion Strength ◽  
Chemical Elements ◽  
Air Flow ◽  
Arc Spraying ◽  
Capital Costs ◽  
Burn Out ◽  
Sprayed Coating ◽  
Spraying Process

The object of research is the control of the process of formation of a spraying air flow and the transfer of particles of liquid metal from electrodes during arc spraying. One of the problem areas of the arc spraying process is the oxidation of the sprayed metal particles by the oxygen of the air flow during their transportation to the sprayed surface. This leads to the formation of a sufficiently large amount of oxides of chemical elements, which significantly deteriorate the adhesion strength and burn out alloying elements that are necessary to obtain a wear-resistant and corrosion-resistant coating. The suitability and durability of coatings during use depends on the strength of adhesion to the substrate. In the course of the study, methods were used to determine the adhesion strength of the coating to the base – the Steffens method and methods for studying the microstructure of coatings were taken as the basis. The data was processed and dependencies were plotted. The proposed method makes it possible to improve the quality of the resulting coating in terms of such an indicator as improvements in chemical composition. And also to influence the chemical composition by controlling the process of transfer of molten metal using a pulsating air flow. The obtained results of approbation of the method allow us to consider it effective, as evidenced by the quality of the obtained coatings. This is due to the fact that the correctness of the formulation and solution of the problem provided adequate results. In contrast to the existing methods, the proposed one makes it possible to significantly influence the amount of harmful oxygen involved in the formation of a sprayed coating, which makes it possible to obtain a sprayed layer with the required performance characteristics. And also allows to improve its quality without significant capital costs. In addition, the issues of resource and energy saving are being addressed, since the burnout of chemical elements decreases and the air consumption during arc metallization decreases. To solve this problem, a simple design of the pulsator is proposed, which provides the ability to control the spray flow by adjusting the level of overlapping of the holes.

Tensile and Shear Test Methods for Quantifying the Ice Adhesion Strength to a Surface

Ice Adhesion ◽  
2020 ◽  
pp. 237-284
Author(s):  
Alexandre Laroche ◽  
Maria Jose Grasso ◽  
Ali Dolatabadi ◽  
Elmar Bonaccurso
Keyword(s):  
Adhesion Strength ◽  
Shear Test ◽  
Test Methods ◽  
Ice Adhesion

Mathematical Modeling of the Process of Operation of the Drying Chamber of a Tower Grain Dryer With a Suction Air Flow

2020 ◽  
pp. 114-121
Author(s):  
Viktor Shvidia ◽  
◽  
Serhii Stepanenko ◽  
Keyword(s):  
Moisture Content ◽  
Air Flow ◽  
Initial Moisture Content ◽  
Material Balance ◽  
Operating Parameters ◽  
Conservation Of Energy ◽  
Grain Moisture ◽  
Optimal Mode ◽  
Drying Chamber ◽  
Main Operating

In the article, a drying scheme in a tower grain dryer has been developed, equations for the conservation of energy and material balance for grain, equations for mass transfer and heat transfer between the drying agent and grain have been drawn up. On their basis, analytical dependences of changes in the temperature and moisture content of grain, moisture content and temperature of the drying agent along and in the width of the drying channel were obtained, depending on the operating parameters (the value of rarefaction in the drying channel, the speed of grain movement along the drying channel, the speed of movement of the drying agent, the initial temperatures of the grain and drying agent, initial moisture content of grain, as well as initial moisture content of drying agent). Their analysis facilitates the work in choosing the optimal mode. The developed analytical dependences of changes in the main drying parameters (moisture and temperature of grain, moisture content and temperature of the drying agent) along the length and width of the drying channel in tower dryers with suction air flow make it possible to link the main operating parameters, which facilitate the choice of rational drying modes.

Control Sensitivity Study for a Hybrid Fuel Cell/Gas Turbine System

2008 ◽  
Author(s):  
Larry Banta ◽  
Jason Absten ◽  
Alex Tsai ◽  
Randall Gemmen ◽  
David Tucker
Keyword(s):  
Fuel Cell ◽  
Gas Turbine ◽  
Hybrid Systems ◽  
Air Flow ◽  
Sensitivity Study ◽  
Test Methods ◽  
System Control ◽  
Control Mechanisms ◽  
Operating Characteristics ◽  
Efficient Operation

The National Energy Technology Laboratory (NETL) has developed a hardware simulator to test the operating characteristics of Solid Oxide Fuel Cell/Gas Turbine (SOFC/GT) hybrid systems. The Hybrid Performance (HyPer) simulator has been described previously, and has contributed to the understanding of SOFC/GT system operation. HyPer contains not only the requisite elements of gas turbine/compressor/generator, recuperator, combustor, and associated piping, but also several air flow control valves that are proposed as system control mechanisms. It is necessary to know how operation of these valves affects the various entities such as cathode air flow, turbine speed, and various temperatures important to the safe and efficient operation of fuel cell/gas turbine hybrid systems. To determine the interactions among key variables, a series of experiments was performed in which the effect of modulating each of the key manipulated variables was recorded. This document outlines the test methods used and presents some of the data from those tests, along with analysis and interpretation of that data in the context of control system design.

Ultrasound Examination – Mean of Analysis of the Layers Properties Deposited Through Different Thermal Spraying Methods

2012 ◽  
Vol 186 ◽  
pp. 169-175 ◽  
Author(s):  
Dand Botez Sorin Constantin ◽  
Gabriel Marius Dumitru ◽  
Bogdan Dumitru ◽  
Dina Viorel-Cristian
Keyword(s):  
Comparative Study ◽  
Adhesion Strength ◽  
Ultrasound Examination ◽  
Thermal Spraying ◽  
Atmospheric Plasma Spraying ◽  
Atmospheric Plasma ◽  
Flame Spraying ◽  
Arc Spraying ◽  
Surface Adhesion ◽  
Better Than

Reconditioning materials by thermal spray metalizing is a rapidly growing field. In this paper we conducted a comparative study of three methods of metal deposition: flame spraying, atmospheric plasma spraying, arc spraying. This was done considering two of the properties of layers obtained in metalizing process: surface adhesion strength and porosity. The result of ultrasound examination by immersion shows that adhesion obtained through APS method is better than the others two obtained through AS and FS methods.

scholarly journals Airflow Dynamics and Aluminum Coating Oxidation Behavior under Electric-Arc Spraying with Airflow Pulsations

2021 ◽  
Vol 11 (18) ◽  
pp. 8444
Author(s):  
Irina Zakharova ◽  
Vyacheslav Royanov ◽  
Valeriy Chigarev
Keyword(s):  
Volume Fraction ◽  
Dynamic Structure ◽  
Electric Arc ◽  
Aluminum Coating ◽  
Arc Spraying ◽  
Metal Oxidation ◽  
Air Supply ◽  
Photo Visualization ◽  
Air Pulsation

The paper aims to investigate the airflow dynamics of electric-arc spraying (EAS) with airflow pulsation. The study is focused on the dynamic structure of the airflow with an obstacle in the form of crossed electrodes at the steady and the pulsating air supply (with a frequency up to 120 Hz). The work was fulfilled using a computer simulation, the airflow “shadow” photo visualization, and the microstructure characterization of the coatings formed. It was found that when air flows along the crossed electrodes with a gap of 2 mm, a depression zone appears in the flow with a pressure drop from 0.56 MPa to 0.01 MPa. The air pulsation resulted in a change in a flow’s dynamic structure towards an increase in the length of the depression zone, which covers most of the arc, affecting the liquid metal oxidation. It is established that the frequency of a droplet formation should match the frequency of the airflow pulsation to minimize the metal oxidation. With the air pulsating at about 65 Hz, the oxide volume fraction in the aluminum coating was reduced by 3.6 times compared to the steady airflow. EAS with airflow pulsation has the potential for technological cost reduction.

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.

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