Adaptive Control of the Atmospheric Plasma Spray Process for Functionally Graded Thermal Barrier Coatings

Functionally graded coatings (FGCs) have a material composition continuously varying through the thickness but uniform in surface parallel to coated substrate. When used as thermal barrier on metallic substrate, coating varies from an almost pure metal near substrate ceramic adjacent outer exposed hot environment. Challenging issues producing high quality FGCs presence of external disturbances with atmospheric plasma spray process (APSP) include controlling mean temperature, axial velocity, and positions constituent particles when they arrive at be coated. The unavoidable fluctuations arc voltage clogging powder delivery system. For two-constituent coating, this work proposes using three modified robust model reference adaptive controllers based σ-modified laws low frequency learning. One controller adjusts current flow rates argon hydrogen into torch. other two adjust distance injector ports jet axis average injection velocity each powder. It is shown numerical experiments that implemented APSP consistently produce high-quality FGCs.