The Effect of Argon as Atomization Gas on the Microstructure, Machine Hammer Peening Post-Treatment, and Corrosion Behavior of Twin Wire Arc Sprayed (TWAS) ZnAl4 Coatings

In the twin wire arc spraying (TWAS) process, it is common to use compressed air as atomizing gas. Nitrogen or argon also are used to reduce oxidation and improve coating performance. The heat required to melt the feedstock material depends on the electrical conductivity of the wires used and the ionization energy of both the feedstock material and atomization gas. In the case of ZnAl4, no phase changes were recorded in the obtained coatings by using either compressed air or argon as atomization gas. This fact has led to the assumption that the melting behavior of ZnAl4 with its low melting and evaporating temperature is different from materials with a higher melting point, such as Fe and Ni, which also explains the unexpected compressive residual stresses in the as-sprayed conditions. The heavier atomization gas, argon, led to slightly higher compressive stresses and oxide content. Compressed air as atomization gas led to lower porosity, decreased surface roughness, and better corrosion resistance. In the case of argon, Al precipitated in the form of small particles. The post-treatment machine hammer peening (MHP) has induced horizontal cracks in compressed air sprayed coatings. These cracks were mainly initiated in the oxidized Al phase.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1111.211 ◽

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.

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CFD Study of Particle and Compressible Flow Interaction for a Twin Wire Arc Spraying System

Volume 7: Fluids Engineering ◽

10.1115/imece2019-10101 ◽

2019 ◽

Author(s):

Raymond Faull ◽

Nicole Wagner ◽

Kevin Anderson

Keyword(s):

Plasma Spraying ◽

Gas Flow ◽

Particle Trajectory ◽

Flow Direction ◽

Phase Changes ◽

Particle Flow ◽

Spray Angle ◽

Arc Spraying ◽

Twin Wire Arc Spraying ◽

Wire Arc Spraying

Abstract Plasma spraying is used in various industries for additive manufacturing applications to apply materials onto a workpiece. Such applications could be for the purpose of repair, protection against corrosion, wear-resistance, or enhancing surface properties. One plasma spraying method is the twin wire arc spraying (TWAS) process that utilizes two electrically conductive wires, across which an electric arc is generated at their meeting point. The molten droplets that are created are propelled by an atomizing gas towards a substrate on which the coating is deposited. The TWAS process offers low workpiece heating and high deposition rates at a lower cost compared to other plasma spraying techniques. As the spray angle for this technique is relatively large (15 degree half angle), particles are lost in the process, lowering the yield of deposited material. The motivation of this project was to constrict the particle flow and reduce the loss of particles that are ejected by the spraying torch. Torch nozzles were designed to help the particle trajectory match the axial flow direction of the atomizing gas flow. Simulations using ANSYS FLUENT Computational Fluid Dynamics (CFD) software was utilized to model both the atomizing gas flow and particle flow for a TWAS system. Various nozzle configurations with arc jet angles between 30–75 degrees showed only small effects on gas flow velocity and shape, with no significant variations in particle flow. These results indicate that nozzle configurations are only one factor in determining particle trajectory, and that phase changes and heat transfer need to be considered as well.

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Asymmetric Melting Behavior in Twin Wire Arc Spraying with Cored Wires

Journal of Thermal Spray Technology ◽

10.1007/s11666-008-9269-y ◽

2008 ◽

Vol 17 (5-6) ◽

pp. 974-982 ◽

Cited By ~ 10

Author(s):

W. Tillmann ◽

E. Vogli ◽

M. Abdulgader

Keyword(s):

Melting Behavior ◽

Arc Spraying ◽

Twin Wire Arc Spraying ◽

Wire Arc Spraying ◽

Cored Wires

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Enhanced Copper Coating Properties Obtained by Electric Wire Arc Spraying Process

Thermal Spray 2000: Proceedings from the International Thermal Spray Conference ◽

10.31399/asm.cp.itsc2000p0685 ◽

2000 ◽

Author(s):

V. Gourlaouen ◽

E. Verna ◽

P. Beaubien

Keyword(s):

Copper Coating ◽

Compressed Air ◽

Arc Spraying ◽

Coating Process ◽

Coating Properties ◽

Electrical Wire ◽

Wire Arc Spraying ◽

Series Of Experiments ◽

Spraying Process

Abstract Among the different wires used in arc spraying, copper is a material of choice in some applications. Its malleability is used to allow an easy machining procedure after spraying. This article focuses on the limitations of the oxidation of copper during arc spraying and its influence on coating process and properties. The aim of this series of experiments was to improve coating properties of copper sprayed with the electrical wire arc spraying process by substituting compressed air with nitrogen. These experiments show that coating properties, as well as electric wire arc spraying process, are strongly influenced by the gas employed as the atomising element.

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Ni-5wt% Al Coatings Deposited by Twin Wire Arc Spraying for Molten Aluminum Attack Protection

10.31399/asm.cp.itsc2021p0700 ◽

2021 ◽

Author(s):

Natalia Brizuela-Colmenares ◽

Juan Muñoz-Saldaña

Keyword(s):

Tool Steel ◽

Performance Test ◽

Molten Aluminum ◽

Arc Spraying ◽

Oxide Content ◽

Process Maps ◽

Twin Wire Arc Spraying ◽

Wire Arc Spraying ◽

Coating Microstructure ◽

And Performance

Abstract Nickel-aluminum alloys are widely used in harsh environments due to their corrosion resistance, high melting temperature, and thermal conductivity. In this work, Ni-5wt%Al coatings were deposited by twin-wire arc spraying (TWAS) on tool steel using a design of experiments approach to study the effect of process parameters on coating microstructure and performance. Test results presented in the form of process maps show how N2 pressure, stand-off distance, and current affect in-flight particle velocity and temperature as well as coating thickness and oxide content. Using this information, optimized coatings were then deposited on test substrates and subjected, along with uncoated tool steel, to several hours of molten aluminum attack. The coated samples showed no signs of physical or chemical damage, whereas the uncoated substrates experienced oxidation, aluminum infiltration, and formation of Fe-Al intermetallics.

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Effect of machine hammer peening on the surface integrity of a ZnAl-based corrosion protective coating

MATEC Web of Conferences ◽

10.1051/matecconf/202031801008 ◽

2020 ◽

Vol 318 ◽

pp. 01008

Author(s):

Alina Timmermann ◽

Mohamed Abdulgader ◽

Leif Hagen ◽

Alexander Koch ◽

Philipp Wittke ◽

...

Keyword(s):

Corrosion Fatigue ◽

Surface Integrity ◽

Protective Coatings ◽

Fatigue Behavior ◽

Turbine Blades ◽

Fatigue Properties ◽

Machine Hammer Peening ◽

Coated Surfaces ◽

Thermally Sprayed ◽

Hammer Peening

Thermally sprayed protective coatings are applied onto many mechanically stressed components such as support structures, shafts, turbine blades or heat exchangers. In addition to the static or cyclic load, a superimposition with corrosion processes occurs in many cases. Thermal sprayed ZnAl coatings are known for their performant corrosion protection properties. Within this context, the potential of ZnAl-based layer systems was analyzed regarding corrosion fatigue behavior. Therefore, a timeand cost-efficient testing strategy based on a corrosion-superimposed load increase procedure was used to estimate the effects of a corrosive attack during cyclic loading. The investigated coating systems were thermally sprayed and partially post-processed with a Machine Hammer Peening (MHP) operation. This treatment was identified as an appropriate technique for compressing and smoothing coated surfaces. The inter-relationships between the parametrization of the MHP process, the resulting surface integrity, and the estimated corrosion fatigue properties were analyzed. The investigations indicate a positive effect of MHP post-processing operations on the surface properties of the ZnAl-based coating system.

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Thermally Assisted Machine Hammer Peening of Arc-Sprayed ZnAl-Based Corrosion Protective Coatings

Journal of Manufacturing and Materials Processing ◽

10.3390/jmmp5040109 ◽

2021 ◽

Vol 5 (4) ◽

pp. 109

Author(s):

Andreas Wirtz ◽

Mohamed Abdulgader ◽

Michael P. Milz ◽

Wolfgang Tillmann ◽

Frank Walther ◽

...

Keyword(s):

Residual Stresses ◽

Protective Coatings ◽

Fatigue Behavior ◽

Wind Waves ◽

Offshore Wind ◽

Coating Materials ◽

Corrosive Media ◽

Machine Hammer Peening ◽

Hammer Peening ◽

Compressive Residual Stresses

Structural elements of offshore facilities, e.g., offshore wind turbines, are subject to static and dynamic mechanical and environmental loads, for example, from wind, waves, and corrosive media. Protective coatings such as thermal sprayed ZnAl coatings are often used for protection, mainly against corrosive stresses. The Machine Hammer Peening (MHP) process is an innovative and promising technique for the post-treatment of ZnAl coating systems that helps reducing roughness and porosity and inducing compressive residual stresses. This should lead to an enhancement of the corrosion fatigue behavior. In this paper, the effect of a thermally assisted MHP process was investigated. The softening of the coating materials will have a direct effect on the densification, residual porosity and the distribution of cracks. The investigation results showed the influence of thermally assisted MHP on the surface properties, porosity, residual stresses, and hardness of the post-treated coatings. The best densification of the coating, i.e., the lowest porosity and roughness and the highest compressive residual stresses, were achieved at a process temperature of 300 °C. A further increase in temperature on the other hand caused a higher porosity and, in some cases, locally restricted melting of the coating and consequently poorer coating properties.

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Machine Hammer Peening

CIRP Encyclopedia of Production Engineering ◽

10.1007/978-3-662-53120-4_300385 ◽

2019 ◽

pp. 1093-1093

Keyword(s):

Machine Hammer Peening ◽

Hammer Peening

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A Study on the Arc Spraying of 7Cr13 Cored Wire and Tribological Properties of the Composite Coating

Thermal Spray 1998: Proceedings from the International Thermal Spray Conference ◽

10.31399/asm.cp.itsc1998p0207 ◽

1998 ◽

Author(s):

B. Xu ◽

S. Ma ◽

J. Wang ◽

J. Tan

Keyword(s):

Bond Strength ◽

Composite Coating ◽

Tribological Properties ◽

High Hardness ◽

Wear Resistant Coating ◽

Arc Spraying ◽

Metallurgical Process ◽

Cored Wire ◽

Wear Resistant ◽

Wire Arc Spraying

Abstract For the purpose of getting high hardness and high wear-resistant coating by arc spraying technology, the arc spraying of 7Cr13 cored wire is adopted in this paper. The metallurgical process of the cored wire arc spraying is discussed. The bond strength, hardness and tribological properties of the composite coating are investigated.

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