Research Progress in Spectroscopic Diagnosis of Plasma Jet Characteristics Under PS-PVD

Zhang, Y; Deng, CG; Mao, J; Deng, ZQ; Luo, ZW

Mao, J (reprint author), Guangdong Inst New Mat, Natl Engn Lab Modem Mat Surface Engn Technol, Guangzhou 510650, Peoples R China.



Plasma spray-physical vapor deposition (PS-PVD), as a new spray technology, combines the advantages of both vapor deposition and thermal spray processes. The plasma characteristics determine the micro structure and properties of the coatings. As a plasma jet characteristic diagnosis technology, optical emission spectroscopy (OES) can realize the in-situ detection of jet characteristics, which is a powerful means to judge the evaporation phenomenon in the jet. This paper introduced the changes of jet characteristics before and after the powder was inject and after the jet impacted the substrate. It shows the calculation of the state of each particle in the jet under the assumption of local thermodynamic equilibrium (LTE) and the theory of broadening, and explores the activities of mass and heat transfer in different regions of the jet. Ar/He has the highest temperature, and Ar has a high enthalpy value, which plays a major role in evaporating the powder. The He condensed jet energy plays a key role in the heating and evaporation of the powder. H2 expands the jet width and reduces the jet temperature to form a mixed layer with dense and columnar structure. Combined with simulation calcnlation and spectroscopy of the jet, it is known that the complex thermal interaction in the spray gun is the main reason for powder heating. The thermal energy and kinetic energy are alternately converted in the expansion/compression zone at the nozzle, and the middle and rear sections of the jet continue to vaporize due to low pressure and high temperature. After reaching the peak, the jet is in the stage of condensation and cooling, and some of the vapor phase atoms are agglomerated into cluster-like particles. The effects of power, current and powder feeding rate on plasma jet characteristics are also summarized.

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