Abstract
The application of optical pyrometry to low- melting- point plasma- sprayed particles can be limited by the plasma light scattered by the particles themselves. From spectroscopic measurements of the plasma between 650 and 1050 nm and using the Mie scattering theory, the intensity of scattered light has been determined in the case of nickel particles sprayed using an Ar/He plasma. The results show that, even in spectral regions between the atomic lines of the plasma gas, the scattered light can be important compared to the thermal emission of the particles. This scattered light leads to values of measured temperatures, which are all the more overestimated because the particle temperature is low and the particle/torch distance short. For a 50- Μm nickel particle at 1550 ‡C, located 10 cm from the torch, the measurement error made with a double wavelength pyrometer is estimated at 100 ‡C.
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This work is based on a presentation made at the 1993 National Thermal Spray Conference, Anaheim, California, USA.
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Gougeon, P., Moreau, C. In-flight particle surface temperature measurement: Influence of the plasma light scattered by the particles. JTST 2, 229–233 (1993). https://doi.org/10.1007/BF02650470
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DOI: https://doi.org/10.1007/BF02650470