Researches On High Temperature Oxidation, Hot Corrosion And Thermal Shock Of Y₂ O₃-ZrO₂ Thermal Barrier Coatings

Y₂O₃ stabilized ZrO₂(YSZ)thermal barrier coatings on high-temperature alloy were prepared by air plasma spraying technology.The surface coatings are respectively micro-YSZ coating and nano-YSZ coating.The bond coating is NiCoCrAlY.Based on the results of the experiments of high temperature oxidation,hot corrosion and thermal shock,the effect of the phase and the microstructure of YSZ coatings on their performance by using the X-ray diffraction(XRD),standard electronic modules(SEM) and energy dispersive spectrometry(EDX).The results show that there are thermally grown oxide(TGO),the main components of which is alumina,between bond coatings and surface coatings after high temperature oxidation.The micro-YSZ coatings have the higher oxidation rates than the nano-YSZ coatings.The high temperature oxidation resistance of nano-YSZ coatings are better.The formation of monoclinic ZrO₂ and YVO₄ crystals as hot corrosion products caused the degradation of YSZ coatings.The reactions of the hot corrosion and the transformation of tetragonal zirconia to monoclinic phase supplement each other.Compared with the micro-YSZ coating,the nano-YSZ coating has superior hot corrosion resistance.The life of nano-YSZ coatings is twice as long as the life of micro-YSZ coatings.The degradation reason of the coatings are mainly two:first of all,the expansion factor of the alloy and the surface coatings does not match,which leads to the degradation due to the residual stress it makes.Secondly,Oxygen through the cracks and matrix reacts with the alloy and the bond coatings.The formation of the oxide leads to the degradation due to the residual stress it makes.