Columnar suspension plasma sprayed coating microstructural control for thermal barrier coating application

Suspension plasma spraying (SPS) is used to perform enhanced YSZ coating with columnar microstructure for thermal barrier coating (TBC) applications. By combination of plasma flow, substrate preparation, suspension formulation and injection or coating kinematic management it is possible to tune SPS coating structure from widely-separated columns to a significantly more compact columnar structure. Among these parameters, substrate roughness control, combined with an adapted coating growth velocity, are identified as the most relevant. An analytical approach is presented to describe columns growth based on coating image analysis. It allows to give the expression of the lateral and normal growth speeds responsible of the columnar structure.