High Stability, High Enthalpy APS Process Based on Combined Wall and Gas Stabilizations of Plasma (Part 1: Process and Coatings Introduction)

The paper describes the major features of a recently developed high voltage – low current air plasma spray (APS) process and torch that is based on combined wall and gas stabilizations of plasma (C+Plasma). It is shown that the C+Plasma process is capable of efficiently generating stable plasmas without drifting or pulsing. Plasma gas selection includes N₂, N₂-H₂, N₂-Ar-H₂, Ar-H₂(He), etc. Availability of stable N₂-H₂ plasmas having enthalpies within 30-70 kJ/sl range offers a new level of APS efficiency and coating quality. The paper includes illustrations of the C+Plasma durability, stability and expanded operating window. The process capability is also illustrated by properties of the advanced MCrAlY bond coatings and dense segmented TBCs (thermal barrier coating).