The Effect Of TiSi₂ Doping On Structures And Properties Of Gd₂Zr₂O₇ Ceramic For Thermal Barrier Coatings

The rapid development of aero-engines has placed increasingly stringent requirements on the performance in ceramic layer materials of thermal barrier coating.The traditional YSZ thermal barrier coating has been unable to meet the requirements of today's aero engines.According to the performance requirements of thermal barrier coating,rare earth zirconate materials have gradually become the focus of research,and are expected to replace YSZ and becoming the next generation of new thermal barrier coating ceramic layer materials.In this paper,the four-component ceramics,Gd₂Zr₂O₇-X TiSi₂?X=0,2.5,5,7.5wt.%?,were prepared by solid-state reaction.The microstructure,phase characteristic,thermal conductivity and thermal expansion coefficient,hardness and fracture toughness properties and CMAS thermal corrosion resistance of the four-component ceramics were studied.The main conclusions of the research work are as follows:?1?The microstructure of different doping content of TiSi₂ in Gd₂Zr₂O₇ was studied.The doped TiSi₂ is completely dissolved in the Gd₂Zr₂O₇ lattice.The original Gd₂Zr₂O₇ is the pyrochlore structure.When the doping content is 2.5 wt.%and 5 wt.%,the ceramics are the pyrochlore structures.The order degree of the pyrochlore structure decreases with the increase of the doping content.When the doping content reaches 7.5wt.%,the structure of the ceramics is transformed into the defect fluorite structure.The microstructure of the ceramics after doping shows obvious grain refinement.The grain refinement phenomenon is the most obvious when the doping amount of TiSi₂ is 2.5wt.%.?2?The physical properties of different doping content of TiSi₂ in Gd₂Zr₂O₇ was analyzed.The thermal conductivity of the doped ceramic material is significantly lower than that of the undoped Gd₂Zr₂O₇,and its thermal conductivity at 1000°C can reach a minimum of 0.916 W/?m?k?for X=5 wt.%.At 1000°C,the thermal expansion coefficient of ceramic materials increases first and then decreases with the increase of doping content.When X=5 wt.%,the thermal expansion coefficient can reach the maximum value of 11.441×10^-6 K^-1.Compared with undoped Gd₂Zr₂O₇,the thermal expansion coefficient of the doped ceramic material is significantly improved.As the doping content increases,the hardness and fracture toughness of the ceramics increase.When X=7.5 wt.%,the fracture toughness can reach a maximum of 1.858 MPa?m^1/2.?3?The thermal corrosion behavior of CMAS materials on Gd₂Zr₂O₇-X TiSi₂?X=0,2.5,5,7.5 wt.%?ceramics was studied.The high temperature corrosion experiments of Gd₂Zr₂O₇-X TiSi₂ for 2.5 h,5 h and 10 h were carried out by CMAS at 1250°C.The results show that the corrosion products are basically similar,and the corrosion products are mainly MgAl2O4,Ca0.15Zr0.85O1.85,Ca2Gd8?SiO4?6O2,Ca3?Zr,Ti?2?Al,Si?3O12,t-ZrO₂.When under the 2.5 h hot corrosion,the thickness of the infiltrated layer produced by CMAS on the thermal corrosion of Gd₂Zr₂O₇-X TiSi₂?X=0,2.5,5,7.5 wt.%?ceramics is almost the same means that the anti-CMAS hot corrosion properties is basically consistent.With the increase of TiSi₂ doping content,the corrosion products Ca_0.15Zr_0.85O_1.85?t-ZrO₂ increase significantly;Anti-CMAS hot corrosion properties of Gd₂Zr₂O₇-X TiSi₂?X=0,2.5,5,7.5 wt.%?ceramics under hot corrosion for 5 h is a little different,the CMAS thermal corrosion infiltration thickness becomes thicker with the increase of TiSi₂ doping content,and Ca_0.15Zr_0.85O_1.85,t-ZrO₂ in the corrosion products also have a significant increase;the thermal corrosion resistance of Gd₂Zr₂O₇-X TiSi₂?X=0,2.5,5,7.5 wt.%?ceramic materials under 10 h of hot corrosion is significantly different,and for the three kinds of TiSi₂ doped ceramics does not significantly penetrate into the layer,and the surface of the ceramics with a doping content of 5 wt.%and 7.5 wt.%has been cracked due to the production and infiltration of large amount of corrosion such as Ca0.15Zr0.85O1.85,t-ZrO2.