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1332 |
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Thermal cyclic behavior of plasma sprayed YSZ/Al2O3 thermal barrier coatings |
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Garip Erdogan / Sakarya Üniversitesi , Turkey Ugur Aral / Sakarya University, Metallurgical and Materials Engineering, TURKEY Fatih Ustel/ Sakarya University, Metallurgical and Materials Engineering, TURKEY Nil Toplan*/ Sakarya University, Metallurgical and Materials Engineering, TURKEY Emin Irfan Karaali/ Sakarya University, Metallurgical and Materials Engineering, TURKEY |
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Thermal barrier coatings (TBCs) were deposited by an Air Plasma Spraying (APS) technique. The coating comprised of 93 wt.% ZrO2 and 7 wt.% Y2O3 (YSZ); NiCrAlY bond coat; and AISI 304L stainless steels substrate. Starting powders were YSZ, and Al2O3 powders were mixed in the compositions of YSZ ? 20, 50 and 80 wt % Al2O3. The mixtures were ball milled for 2h by using ZrO2 balls to provide homogenous mixtures. The coatings were formed using a METCO 3MB plasma spray gun on stainless steel substrates. Electron microscopy was used to analyze the microstructures of powders and coated samples. Thermal cyclic lives of the TBC were determined as a function of bond coat and top coat surface roughness. Thermal shock test was performed over the specimens, holding of specimens at 1000 °C for 5 min and 2 min forced air quenching. The samples were directly pushed into the furnace at 1000 °C. It was observed that the final deposition temperature has great impact over the thermal shock life. The results were more prominent in forced air quenching tests, where the lives of the TBCs were observed 5?66 cycles between. Further, the bond coat surface roughness varied by employing intermediate grit blasting just after the bond coat spray. It was observed that with decrease in bond coat roughness, the thermal shock life decreased slightly. |