CHARACTERIZATION OF THE WIRE ARC SPRAY PROCESS VIA IMAGE ANALYSIS, IN-FLIGHT PARTICLE CHARACTERISTICS AND COATING PROPERTIES

摘要

To have a better understanding of the physical phenomena in wire arc spraying process, we investigated droplet formation by discriminating particles resulting from the anode and the cathode wire atomization. The investigation showed that by spraying simultaneously two different materials, steel and copper, particle trajectory and their diameter distribution, the results related to the processing parameters. By analyzing the characteristics of captured particles implementing image analyses, the crossover direction of in-flight particles was demonstrated. The droplets produced by the anode were bigger than those issued from the cathode and their fraction number, which was also more important. In addition, some important modifications in particle characteristics were observed by inverting a material by the other at the anode and at the cathode. The melting temperature of copper as anode was a critical parameter and was responsible for the copper vaporization. In-flight particle characteristics (temperature, velocity, and diameter) were also determined by using a Fast-Infrared Pyrometer (FIP DPV2000 type diagnostic system). Concerning particle diameter distribution, a good agreement was discovered for the two approaches (in-flight and a posteriori analyses). Major influences of the electrode nature and the radial location on particle velocity and temperature distribution, was pointed out. Finally, quantitative analyses of coating compositions corroborated previous results. Indeed, the coating thickness distribution was largely dependent on the anode nature. Next, the role of each electrode was related to the droplets formation and thus, optimized operating parameters of the arc spray process were deduced.