Formation of vertical cracks in solution-precursor plasma-sprayed thermal barrier coatings

When tailored to make durable thermal barrier coatings (TBCs), the Solution Precursor Plasma Spray (SPPS) process produces a microstructure containing uniformly vertical cracks. These cracks provide a high degree of strain tolerance to the ceramic top coat. In order to understand the formation of vertical crack in SPPS process, coatings of various thicknesses were deposited on a variety of substrates with vastly different thermal properties. These coatings were characterized in the as-sprayed state and after heat treatment. It has been determined that the tensile stress derived from the pyrolysis of precursor occurring during coating deposition or post heat-treatment is the major driving force for the formation of vertical cracks in SPPS TBCs.