Metallurgical and process comparison of vacuum plasma spray forming on internal and external surfaces—A technical note

Vacuum plasma spray (VPS) forming is being developed and characterized for near-net-shape fabrica-tion of aerospace components. Applications require VPS forming of structural materials in both mono-lithic form (i.e., freestanding shapes) and as integral parts of complex components (e.g., a liner for a rocket engine combustor). In these applications the material deposited on both the inside and the outside of large and small components must meet strict quality requirements. This paper discusses metallurgical and processing comparisons between depositing material on inside and outside surfaces of symmetrical shapes. Specific examples of material properties (e.g., grain structure, hardness, and tensile properties) and process parameters (e.g., standoff distance and gun design) are discussed in terms of the fabrication of large rocket engine combustion chambers.