Spectroscopic diagnostics for a low-pressure plasma spray deposition system

Abstract

Emission spectroscopy was utilised to characterise an arc-driven d.c. plasma jet used for low-pressure plasma spray deposition. Line of sight argon emission line intensities were measured in the wavelength range from 400 to 850 nm; nitrogen rotational spectra were measured from 300 to 450 nm. The Ar0 excitation temperature was calculated using the Boltzmann slope method, assuming partial local thermodynamic equilibrium (LTE). The degree of over-population of some energy states was also calculated. Data showed that partial LTE did not exist; therefore, calculated temperatures represent Ar electronic state population distribution. Temperatures ranged from 4220 to 7870 K and varied with arc power, chamber pressure and spatial position.