Process Characterization
Real-time monitoring of in-flight particle characteristics (such as temperature, velocity,
and size) provides a useful tool for the operator of a thermal spray system to control the quality
of the produced coating as it is being produced.
The apparatus used for in-flight particle characterization in the present work is the DPV-
2000 system (manufactured by Tecnar Automation Ltd., Montreal, QC, Canada). This optical
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monitoring device has a sensing head that consists of a focusing lens, a two-slit photomask, and
optical fibers (Figure 2.2). This sensing head is aimed perpendicular to the spray particle flow
(Figure 2.1) and can be moved (with two degrees of freedom) to scan a cross section of the spray
plume. This device measures properties (velocity, temperature and size) of individual particles
by analyzing the infrared radiation emitted by each particle passing through the field-of-view of
its sensing head. A photomask with two vertical slits is fixed in front of the optical sensor so that
two peaks are recorded whenever a particle is detected. (Figure 2.3). Two photomasks are
supplied with the device allowing to measure particle velocities below and over 400 m/s. The
low velocity mask, P4590170, was used in these experiments.