Wire Composition: Its Effect on Metal Disintegration and Particle Formation in Twin-Wire Arc-Spraying Process
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JTTEE5 22:352–362 DOI: 10.1007/s11666-012-9870-y 1059-9630/$19.00 ASM International
Wire Composition: Its Effect on Metal Disintegration and Particle Formation in Twin-Wire Arc-Spraying Process W. Tillmann and M. Abdulgader (Submitted June 26, 2012; in revised form November 21, 2012)
The wire tips in twin-wire arc-spraying (TWAS) are heated in three different zones. A high-speed camera was used to observe the melting behavior, metal breakup, and particle formation under different operating conditions. In zone (I), the wire tips are melted (liquidus metal) and directly atomized in the form of smaller droplets. Their size is a function of the specific properties of the molten metal and the exerting aerodynamic forces. Zone (II) is directly beneath zone (I) and the origin of the extruded metal sheets at the wire tips. The extruded metal sheets in the case of cored wires are shorter than those observed while using solid wires. In this study, the effects of adjustable parameters and powder filling on melting behavior, particle formation, and process instability were revealed, and a comparison between solid and cored wires was made. The findings can improve the accuracy of the TWAS process modeling.
Keywords
atomization, cored wire, diagnostics, heat transfer, image analysis, iron, tungsten carbide
1. Introduction A heat source is utilized in thermal-spraying processes to melt the feedstock. The molten or semi-molten material is propelled toward a prepared substrate surface by expansion of the process and atomization gases. The subsequent impact of the in-flight particles on the substrate generates a coating. Therefore, the efficiency of a thermal-spraying process is dependent on the energy consumed for melting the feedstock and the attained deposition rate. The twin-wire arc-spraying (TWAS) process is thus the most economical coating process among the thermal-spraying techniques with respect to the above mentioned reasons. In addition, by utilizing cored wires, the TWAS process exhibits the highest variety in feedstock. Coatings produced by means of TWAS show
This article is an invited paper selected from presentations at the 2012 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Thermal Spray 2012: Proceedings of the International Thermal Spray Conference, Air, Land, Water, and the Human Body: Thermal Spray Science and Applications, Houston, Texas, USA, May 21-24, 2012, Basil R. Marple, Arvind Agarwal, Laura FilofteiaToma, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Andre´ McDonald, Ed., ASM International, Materials Park, OH, 2012. W. Tillmann and M. Abdulgader, Institute of Materials Engineering, Technische Universita¨t Dortmund, Dortmund, Germany. Contact e-mail: [email protected].
352—Volume 22(2-3) March 2013
some disadvantages such as high porosity, high oxidation, limited reproducibility, and low adhesion strength. The attainable coating quality is controlled by the temperature, size, and veloc
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