leaks are bad.” He explained any leak can lead to contamination, significant drops in control pressure, and plasma gun restrike instability, making leaks a condition not to be ignored. On the equipment side, he noted power supplies for plasma and electric arc spraying only pretend to be DC. Actually they are really “noisy” AC superimposed on really “dirty” DC. On arc starting, he commented most highfrequency starters are essentially a spark-gap transmitter, similar to what was used in the early days of Morse Code transmission. If your arc start takes more than 100 ms, you have a problem. It could be any number of things, including water-cooled cables, bad gas, moisture, high-frequency components, point gap, or dirt and oil. With surface preparation, he noted that to increase surface roughness, it is more effective to increase grit size rather than increasing pressure or dwell times. Wires for electric arc spraying should not have a cast of more than 30 in. Powder size and mass affect splat cooling rate the most. His presentation closed with the statement, “Handles do not belong on high-energy devices such as plasma guns, HVOF guns, and cold spray guns. They just encourage people to grab them and create an unsafe situation.” Four new member companies, De- Wal, Kermetico, Lincoln Electric, and Mason Global Management, were also given a chance to speak about their products and services. Upcoming Events At FABTECH 2016 in Las Vegas, Nev., Nov. 16–18, there will be a free half-day class on “Thermal Spray Basics: Putting Coatings to Work.” Next year, the annual ITSA conference is scheduled to be in Albuquerque, N. Mex. If you are interested in becoming an ITSA member company or want to find out more about the organization, go to thermalspray.org. 48 WELDING JOURNAL / JULY 2016 WJ ANDREW CULLISON (cullison@aws.org) is publisher, Welding Journal. For info, go to aws.org/adindex For info, go to aws.org/adindex
Welding Journal | July 2016
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