Arc-Plasma Wire Spraying: An Optical Study of Process Phenomenology
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JTTEE5 24:1566–1573 DOI: 10.1007/s11666-015-0356-6 1059-9630/$19.00 ASM International
Arc-Plasma Wire Spraying: An Optical Study of Process Phenomenology I.P. Gulyaev, A.V. Dolmatov, M.Yu. Kharlamov, P.Yu. Gulyaev, V.I. Jordan, I.V. Krivtsun, V.M. Korzhyk, and O.I. Demyanov (Submitted August 17, 2015; in revised form October 30, 2015) In the present paper, we report on the results of an experimental study of heat- and mass-transfer processes in a Plazer 30-PL-W plasma-jet facility used for arc-plasma wire spraying. Using an original optical diagnostic system, we have studied melting behavior of the metal wire, break up and atomization of liquid metal. For the first time, experimental data on the in-flight velocity and temperature of spray particles in arc-plasma wire spraying were obtained. In spite of moderate particle velocities (about 50 m/ s), the obtained steel coatings proved to have a low porosity of 1.5%. While studying the spraying process of tungsten wire, we observed the occurrence of anomalous high-velocity (over 4000 m/s) outbursts ejected from the surface of liquid metal droplets. The nature of such outbursts calls for further study.
Keywords
coatings, droplet breakup, optical diagnostics, plasma-arc wire spraying, temperature measurement, velocity measurement
1. Introduction Presently, thermal spray technologies (Ref 1, 2) are deeply integrated in many industrial manufacturing processes ranging from gas-turbine engines to microelectronics (Ref 3, 4). The choice of the particular thermal spray method (Ref 1, 2, 5-7) (plasma, detonation, HVOF, arc spray, etc.) depend on the type of the material to be sprayed, coatings properties requirements, throughput efficiency and cost of the spraying process and equipment. One of the new thermal spray processes is plasma-arc wire spraying, which features a low cost and high throughput. A specific feature of the method is the use of electric arc both for melting of a feedstock wire (consumable electrode) and for heating of a plasma gas being used for atomization and acceleration of sprayed material (Ref 8, 9). A shielding gas is used to shape the plasma jet and protect it from mixing with ambient atmosphere (Fig. 1). Here, the heating and melting of wire material is due to the heat flux from the plasma flow; due to the heat release at the anode attachment spot of the arc; and due to Joule heating of the wire. Similar to twin-wire arc spray
I.P. Gulyaev, S.A. Khristianovich Institute of Theoretical and Applied Mechanics SB RAS, Novosibirsk, Russia and Yugra State University, Khanty-Mansiysk, Russia; A.V. Dolmatov and P.Yu. Gulyaev, Yugra State University, Khanty-Mansiysk Russia; M.Yu. Kharlamov, I.V. Krivtsun, V.M. Korzhyk, and O.I. Demyanov, E.O. Paton Electric-Welding Institute of the NAS of Ukraine, Kiev, Ukraine; and V.I. Jordan, Altai State University, Barnaul, Russia. Contact e-mail: Gulyaev@ itam.nsc.ru.
1566—Volume 24(8) December 2015
(TWAS), completely molten metal particles enter the plasma flow and build up a coating. At its current developmental
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