Segmentation cracked coatings are promising candidates for thermal barrier coatings (TBC) because of their high strain tolerances. By atmospheric plasma spraying (APS), cylindrical stand-alone YSZ coatings with and without segmentation cracks were fabricated. The diameter of the tubes was 10 mm, and the thickness of the coatings approximately 1 mm. The segmentation crack densities were in the range up to 3.5 cracks/mm, while the porosity amounted for all coatings between 5% and 7%. Further details of the spraying process and the obtained microstructures will be given and discussed. The samples were tested in an uniaxial high temperature compression rig to measure the stress relaxation. The comparison of the stress relaxation measurements yielded a different performance of segmented and non-segmented coatings with advantages for the cracked ones. It was observed that the cracks increase the resistance to stress relaxation.

Plasma-sprayed 7 wt.% Y 2 O 3 -ZrO 2 (YSZ) stand-alone coatings were subjected to 10, 50 and 100-hr heat treatments at 1200°C, followed by mechanical testing in compression at 25°C, 1050°C, and 1200°C. The mechanical tests performed on the samples included cyclic loading/ unloading, stress-relaxation, and creep. In cyclic compression tests at 25°C, it was observed that the YSZ coating that had been heat-treated for 50-hr at 1200°C demonstrated a higher modulus and more strain hysteresis as compared to an as-sprayed sample. As heat-treatment time increased, the YSZ stand-alone coating demonstrated less relaxation of the initial applied stress for stress-relaxation tests run at 1050°C and 1200°C. The steady-state creep rate was observed to decrease with increasing heat-treatment time prior to testing; as expected, the steady-state creep rate increases when the testing temperature was increased from 1050°C to 1200°C. Density (via Archimedes’) and phase analysis (via X-ray diffraction) were performed on YSZ coatings before (i.e. as-sprayed) and after heat-treating at 1200°C. Porosity was observed to decrease only slightly (~1%) after a 100-hr heat-treatment at 1200°C as compared to the as sprayed porosity. The high-yttria metastable tetragonal phase observed in the as-sprayed coatings was observed after a 100-hr heat-treatment at 1200°C. The same metastable tetragonal phase was also observed after a 100-hr heat-treatment at 1200°C followed by a 3-hr stress-relaxation test at 1200°C.