Project Title:

MICROWAVE DRIVEN PLASMA SPRAYING

Physical Sciences Inc.
20 New England Business Center
Andover, MA 01810

93-1-04     20   0003

MICROWAVE DRIVEN PLASMA SPRAYING

Abstract:

A new method of producing a hot plasma/gas stream for "plasma
spraying powdered materials is proposed. The method uses
microwaves to produce and heat the plasma. The objective of the
program is to experimentally demonstrate the new method and
establish scaling to commercially interesting powers. The project
consists of modifying apparatus supplied by PSI for plasma
spraying, then measuring the output flow temperature and
velocities and testing the ability to spray materials. Microwave
driven plasma spraying offers several advantages over
conventional arc-driven plasma sprayers. Microwave discharges
require no electrodes, thus eliminating the problems of wear
associated with these elements. The discharges are also more
stable, potentially improving the quality of the sprayed coating
and reducing operating noise. In addition, a variety of gases,
including inexpensive nitrogen, can be used as the working fluid.
Ohmic and thermal losses are low, resulting in potentially high
efficiencies. The discharge can operate at higher pressures at
high temperatures, resulting in the high velocities of HVOF but
at the high temperatures of plasma devices. This results in
higher quality coatings of high melting temperature materials,
such as ceramics. This capability offers significant improvement
over the current state-of-the-art plasma spray technology.

The potential exists that microwave-based plasma sprayers, with
their superior performance, gas handling capability, and
reliability/lifetime can result in a very competitive commercial
system, thereby replacing a large fraction of the existing plasma
sprayers. Plasma spraying is a very large business area, with the
market for plasma spray guns being $20M/year in the U.S. alone. 

Plasma spray, microwaves