Abstract

Wire arc spraying has traditionally filled metallic coating needs for low end users, while higher quality coatings required the use of higher cost systems. A new high velocity wire arc spray device has been developed through a NASA SBIR project whose high particle velocity capabilities could provide high quality coatings while keeping costs well below those associated with HVOF and plasma spray approaches. In addition, this technique achieves these high velocities in an extremely short acceleration path. This new device employs a pulsed plasma as the accelerative medium for the molten droplets. This pulsed plasma is capable of accelerating the droplets from the tips of the wires up to high velocities and atomizing them to very fine size. This results in a fine microstructure in the deposit. Recent experiments using a Control-Vision system measured velocities for aluminum droplets in the range of 950-1500 m/s and stainless steel droplets in the range of 850 m/s and 925 m/s. These velocities are achieved with an acceleration distance of only 3.2 cm, thus making this process an ideal candidate for coating the interior of automotive cylinder bores and other areas where only a short acceleration region is available.

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