Temperature Profile in YPO4 Laden Plasma Jet and Its Evolution with Arc Current and Powder Loading

Abstract

YPO 4 is emerging as one of the fittest candidates for anti-corrosion thermal-barrier coatings suitable for aggressive environments at high temperature. The study presents an in situ investigation of the axial distribution of temperature in an YPO 4 laden plasma jet using a modified Boltzmann plot technique that does not require Abel inversion and suited for jets involving instabilities and thermal non-equilibrium. Investigated operating current range (528 to 730 A) and powder flow rates (5.37 to 13.62 g/min) are found to ensure effective development of YPO 4 coating. The nozzle exit temperature is found to vary from 11000 to 15000 K depending on arc current and powder loading. With no powder loading, the axial temperature distribution mostly follows a Gaussian-like profile at all set currents. With powder feeding, the profiles get transformed into nearly linear drop with local spiking of temperature at several axial locations. The tendency becomes more intense at higher arc current. Formation of shock trains in the jet with powder loading is suspected to be the underlying reason behind spatial spiking of temperature. Exhibited poor dependence of the nozzle exit temperature on powder loading at lower arc currents is found to get reversed at higher arc currents.