The Gaseous Material Capacity of Open Plasma Jet in Plasma Spray-Physical Vapor Deposition Process

Plasma spray-physical vapor deposition (PS-PVD) process, emerging as a highly efficient hybrid approach, is based on two powerful technologies of both plasma spray and physical vapor deposition. The maximum production rate is affected by the material feed rate apparently, but it is determined by the material vapor capacity of transporting plasma actually and essentially. In order to realize high production rate, the gaseous material capacity of plasma jet must be fundamentally understood. In this study, the thermal characteristics of plasma were measured by optical emission spectrometry. The results show that the open plasma jet is in the local thermal equilibrium due to a typical electron number density from 2.1×10¹⁵ to 3.1×10¹⁵ cm^-3. In this condition, the temperature of gaseous zirconia molecules can be equal to the plasma temperature. A model was developed to obtain the vapor pressure of gaseous zirconia molecules as a two dimensional map of jet axis and radial position corresponding to different plasma temperatures. The overall gaseous material capacity of open plasma jet, take ZrO₂ for example, was established. This approach on evaluating material capacity in plasma jet would shed light on the process optimization towards both depositing columnar coating and a high production rate of PS-PVD.