The aim of this paper is to study the influence of plasma spray set-up parameters, such as the hydrogen percentage in the plasma forming gas and arc current, as well as powder injection parameters: the carrier gas flow rate and injected particle size on the melting, vaporization and velocity of particles of a Fe-Cr based alloy and stainless steel AISI 316L. Particles were collected in flight in a cylinder where they were quenched by argon jets to prevent there flattening at impact and chemical interaction with their environment. After collection, particles were analyzed by SEM, EDS and X-ray diffraction. When the injected particle size was between 60 and 100 µm, particles collected in flight exhibit complex shapes with a mean diameter of 40 µm, and the higher was the percentage of hydrogen the smaller was the resulting mean diameter. This probably corresponds to an inefficient cooling by the argon jets resulting in particles impacting at the bottom of the collector and partially exploding. When the injected particle size was between 10 and 35 µm, collected particle were nearly spherical with almost the same mean diameter, but then the oxidation changed with spray parameters. Measurements of temperature and velocity of the in-flight particles during plasma spraying were done using the Spray Watch (Oseir, Finland) equipment. Relationships between in-flight particle parameters and characteristics of the collected particles were found. Abstract only; no full-text paper available.

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