Analysis Of Tensile Failure And Mechanical Properties Of (Gd_0.9Yb_0.1)₂Zr₂O₇ Systems By Using Digital Image Correlation Technique

Thermal barrier coating(TBC)materials have become critical insulation materials for hot end parts of high performance aeroengines.As the turbine inlet temperature exceeds 1200?,the conventional 8 wt%Y2O3-ZrO2 material undergoes high temperature phase transformation,resulting in large volume deformation of the coating and failure.In many novel high temperature thermal insulation protective coating systems,(Gd0.9Yb0.1)2Zr2O7(GYbZ)has attracted researchers' attention because of its higher melting point,better phase stability and lower thermal conductivity.In this paper,the multi layer shear lag model applied to the tensile fracture analysis of coatings is firstly improved.Secondly,the novel GYbZ coating samples were successfully prepared by plasma spraying process,and real time tensile fracture tests were completed at different temperatures.Finally,the failure mechanism of tensile fracture of the novel GYbZ coating is summarized.The main conclusions are summarized as follows:(1)Based on the traditional two layer structure shear lag model and the three layer shear lag model deduced by our group,energy criterion is used to derive the expressions of fracture energy and fracture toughness when the coating is cracked.The three layer shear lag model was further improved,to provide an important basis for evaluating the reliability and life prediction of TBCs.(2)With the help of digital image correlation technology and high temperature loading systems,X-ray diffractometer and scanning electron microscope are auxiliary.The phase and microstructure of GYbZ novel TBC prepared by plasma spraying were characterized.The elastic modulus and residual stress of each layer material of GYbZ coating system at different temperatures were tested.The results show:the GYbZ coating was a fluorite structure and the porosity of the coating was 10.3%.It was found that with the increase of temperature in the range of experimental temperature,the elastic modulus of GYbZ coating material first decreased from 125GPa to 100.4GPa,then increased to 162.9GPa,the elastic modulus of Incone1600 alloy base material decreased from 214.0GPa to 90.6GPa,the residual stress within the GYbZ ceramic layer first decreased from-125.3MPa to-100.5MPa,then increased to-162.0MPa,the residual stress within the adhesive layer decreased from-237.5MPa to-142.5MPa.(3)The GYbZ TBC system prepared by plasma spraying was tensile tested at high temperature using digital image correlation technology and a high temperature loading system,and combine with the three layer shear lag model for analysis.The results show:with the increase of temperature in the range of experimental temperature,the fracture strength of GYbZ coating first decreased from 228.7 MPa to 193.7 MPa,then increased to 337.2 MPa,and then decreased to 226.3 MPa,the fracture energy of GYbZ coating first decreased from 79.6 J/m2 to 71.8 J/m2,then increased to 184.1 J/m2,and then decreased to 80.1 J/m2,the fracture toughness of GYbZ coating first decreased from 3.16 MPa m1/2 to 2.69 MPa m1/2,then increased to 4.87 MPa m1/2,and then decreased to 3.61 MPa m1/2,the fracture strength of the adhesive layer decreased from 1494.3 MPa to 712.4 MPa,the interfacial shear strength of the ceramic layer and the adhesive layer decreased from 1082.1 MPa to 428.8 MPa,the interfacial shear strength of the adhesive layer and the substrate decreased from 1757.7 MPa to 1230.2 MPa.