High Stability, High Enthalpy APS Process Based on Combined Wall and Gas Stabilizations of Plasma (Part 2: Plasma Properties and Process Operating Window)

A recently developed air plasma spray (APS) process and a torch based on the combined wall and gas stabilizations of plasma (C+Plasma) has demonstrated extremely wide operating window and capability to efficiently generate both argon and nitrogen based plasmas including high enthalpy N₂- H₂ ones. The present paper aims to describe new areas of the extended C+Plasma operating window, in which a significant increase in the APS sprayed coating quality and process efficiency should be expected. The paper includes a brief analysis of properties of different plasmas as well as specifics of coating formation. Analysis showed that with the high enthalpy N₂-H₂ plasmas a significantly higher heat transfer potential and higher flexibility in controlling the particle acceleration can be achieved than with the argon based plasmas. Consequently, C+Plasma can enable better treatment of sprayed particles, which results in better deposit efficiency and improved coating properties.