Particle in-flight behavior and its significance in determining the microstructure and mechanical properties of zirconia based thermal barrier coatings

The present study aims to elaborate the particle in-flight behavior during plasma spraying and its significance in determining the microstructure and mechanical properties of plasma sprayed yttria partially stabilized zirconia (YPSZ) based thermal barrier coatings (TBCs). The as-sprayed YPSZ coatings were characterized in terms of the defects (such as porosity, unmelted particles, cracks and micro-cracks), hardness, elastic modulus and fracture toughness. The results showed that the total defects percentage, porosity, unmelted particles and crack content were found to decrease significantly with the improvement of temperature of in-flight particles. The mechanical properties were associated with the microstructure of these coatings, such as total defects, porosity, unmelted particles and cracks. It was confirmed that the mechanical properties, including hardness, elastic modulus and fracture toughness, notably enhanced with the total defects, porosity, unmelted particles and cracks decreased. The SAPS (supersonic atmospheric plasma spraying) coatings sprayed at 3401 ± 3.76 °C and 482 ±2.18 m/s and a spraying distance of 100 mm possessed the lowest microstructural defects percentage and the most favorable mechanical properties among the 15 types coatings.