Study on Thermal Shock Resistance of Thermal Barrier Coatings
Qiao Haichao Ding Chuanxian (Shanghai Institute of Ceramics,Academia Sinica)
Thermal shock resistance of zirconia based thermal barrier coatings with andwithout a NiAl bond layer was investigated by using a high enthalpy and velocityplasma torch at power level of 25kW and forced cooling air with pressure of 3×10~5 Pa.Measurement showed that the temperature on the coating surface after hea-ted for 3 s reached 1000 to 1100℃.The temperature difference across the ceramiccoating was about 700℃.Experimental results demonstrated that the ceramic metallicduplex coating system was superior to the single ceramic system in thermal shockresistance,and its thermal shock resistance increased in the following order:ZrO_2+4.6wt% CaO+NiAl,ZrO_2+16.3wt% Y_2O_3+NiAl,ZrO_2+9.2wt% Y_2O_3+Ni-Al.Analysis indicated that the coating failure was mainly due to the continualthermal shock stress and crack propagation driven by strain energy.The incorpora-tion of the metallic bond coating which could delay the growth of cracks effective-ly enhanced the thermal shock resistance because i(?) broadened the strain limita-tion and changed the energy absorption mechanism of the ceramic coating.
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