Experimental Study of the Impact of Substrate Shape and Tilting on Particle Velocity in Suspension Plasma Spraying

Abstract

Suspension plasma spraying has shown its capacity to deposit finely structured coatings with a wide range of microstructures including columnar microstructures that are generally sought in thermal barrier coating applications for gas turbines. However, some challenges are still to be taken up before the application of the technology at an industrial scale. One deals with the deposition of a uniform and reliable coating on a complex shape substrate. This work offers an experimental observation of submicron particle streams close to the substrate in order to understand mechanisms of deposition. Effects of the substrate shape and tilting were investigated on particle velocity, directions and coating growth. It was shown that particle velocities and directions are disrupted by the substrate presence up to 10mm upstream. When the substrate is a cylinder or in a tilted orientation to the plasma jet, particles kinetic behaviour is less affected. Finally, submicron particle velocity vectors orientation near impact greatly shape the coating morphology. When impacting with a 40° angle of incidence, columns appeared on beads, contrary to submicron particle streams impacting orthogonally to the substrate surface.

Progress in ceramic materials and structure design toward advanced thermal barrier coatings

“…The columnar top coat also suffers from corrosion due to the easy infiltration of reactants into the inside top coat via columnar pores, although columnar top coat has high thermal stress tolerance and potentially long thermal cyclic lifetime [272,273]. However, they are easily attacked by corrosion agents due to their gap-type structure.…”