Abstract No.:
3879

 Scheduled at:
Thursday, May 22, 2014, Hall H3 4:40 PM
Arc Spraying & Laser Spraying


 Title:
3D µCT and SEM analysis of resolidified tips of cored wires used in twin wire arc spraying

 Authors:
Jens Nellesen* / RIF e.V. - Institut für Forschung und Transfer, Germany
Mohamed Abdulgader / Institute of Materials Engineering, Technische Universität Dortmund, Germany
Wolfgang Tillmann/ Institute of Materials Engineering, Technische Universität Dortmund, Germany
F. Beckmann/ ,

 Abstract:
The inhomogeneity of the spraying plume in thermal spraying techniques is mostly dependent on the type of feedstock used. It is more homogeneous for coating processes where powdery metallic or non-metallic feedstock is deposited (like in plasma or HVOF spraying). In contrast, if the in-flight particles are atomized from a melting bath (like in Twin Wire Arc Spraying (TWAS)) the spray jet is less homogeneous. This is due to the fact that these particles are generated by the impingement of fast and continuous flowing air upon the melting tips of electrically conductive wires.
This work aims to contribute to the understanding of the initiation of such particles in the TWAS process. For this purpose, cored wires filled with different types of W-rich particles were sprayed. After stopping the TWAS process, the tips of these cored wires were detached and analyzed. Using the 3D µCT, the detached tips were imaged to investigate how the filling powder interacts with melted part of the velum. The visual inspection of the 3D µCT images has conspicuously shown that the resolidified melting bath at the most outer end of the cored wires is interspersed by both spherical and irregular-shaped W-rich particles. This irregular shape suggests a partial melting of the W-rich particles. Moreover, cavities in the melting bath of the wire tips were discovered, which is a clear indication of the high temperature caused by arc ignition. After the non-destructive analysis, metallographic sections of the wire tips were investigated by scanning electron microscopy (SEM) which revealed also a melting at the periphery of the filling powder particles.


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