Nondestructive Measurement Of Thermally Grown Oxide Residual Stress On Curved TBCs Using PLPS

Thermal barrier coating,used on the high pressure turbine blades of high-performance aeroengines,has long been listed as the key technology of high-temperature thermal protection for aero-engines by aviation development departments of various countries.In the actual service environment,the thermally grown oxide?TGO?formed at the interface between the ceramic layer and the bonding layer can further prevents the oxidation of the internal metal,but is also the root cause of interface cracking and spallation of the ceramic layer.Non-destructive methods used to measure the residual stress and stress distribution in TGO with real turbine blade morphology is important in judging the overall quality and service life of the thermal barrier coatings.In this paper,the electron beam physical vapor deposition?EB-PVD?method was used to prepare thermal barrier coaintgs with different substrate curvatures(curvatures:0mm^-1,0.002 mm^-1,0.025 mm^-1,-0.03 mm^-1,0.2 mm^-1),as well as YSZ columns with different inclination angles?0°,5°,10°?on a flat surface.The photo-stimulated luminescence piezo-spectroscopy?PLPS?method was used to measure the evolution of the residual stress of TGO of the curved thermal barrier coating with thermal cycling and the residual stress distribution after 10 thermal cycles.The main research contents are as follows:?1?The PLPS was used to measure the residual stress of TGO for the planar thermal barrier coatings with different inclination angles,and the effect of inclination on the results of PLPS was investigated.The results showed that the inclination of the columnar crystal did not show a significant influence on the final detection results of the PLPS,but it affected the collection of the PLPS fluorescence signal to varying degrees.?2?Thermal barrier coatings with different curvature substrates were prepared by EB-PVD method.The influence and analysis of the substrate curvature on the micro-morphology of the thermal barrier coatings after EB-PVD preparation were investigated.It was found that the columnar crystal structure of the ceramic layer of the curved substrate tended to incline when prepared by EB-PVD.It was found that the sample coating with a curvature of 0.2 mm^-1 peeled off first.?3?The PLPS was used to detect the residual stress of the curved thermal barrier coating specimens under different thermal cycles.The residual stress of the normal thermal barrier coating was compared.The evolution of the residual stress was analyzed.The samples of the curved thermal barrier coating remained the same,all of which showed a rapid increase in stress in the initial stage and subsequently decreased.The residual stress mapping analysis was carried out on the curved samples having completed 10 thermal cycles.It was found that with the increase of the curvature,the residual stress value distribution was more discrete,and the concave curvature sample showed a uniform distribution as the flat sample.The correlation between the residual stress and the life of the curved thermal barrier coating was studied.The results showed that the growth rate and rumpling of TGO will significantly influence the life time of TBCs,which was attributed to the effect of curvature.