Studies On The Effect Of Interface Topography Upon Internal Stress In The Thermal Barrier Coatings

In the face of the more and more higher request to the hot end components working temperature, the thermal barrier coatings technology is being generally used in order to obtain the higher material application temperature. The thermal barrier coatings is a kind of ceramic coating, which is usually deposited on the thermostable metal surface, having a good heat insulation effect. It can keep the substrate material from the high-temperature oxidation and the corrosion, and can reduce the substrate the operating temperature, and can also enhances the fuel gas temperature. So that it can improve the efficiency of the hot end part the efficiency, and lengthens its service life. Therefore, the thermal barrier coatings technology has already became one of the most active research topics in the field of international high temperature coating in recent years.But the serious thermal-expansion coefficient differences between the substrate metal and the ceramic coating doesn't only lead to the stress of this two kinds materials is not suited ,but also cause the coating to strip along the contact surface. Therefore both the early time stripping and the fallibility of the servicing life of the thermal barrier coatings is still the big problem of the practical application. It has been proved that there're various factors which are related to the invalidation of the thermal barrier coatings, such as coating processing craft, the hot load materials withstanding, geometry appearance of the thermal barrier coating and so on.Therefore, the purpose of this article is to inquire about the relationship between the geometry appearance of thermal barrier coating and the internal stress of coatings. We specially study this relationship in two case, one is the hot load alone affects ,and the other is the hot load and the mechanical load simultaneously affect the system of coatings. We use some different curves to simulate the contact surface profiles, and make some stresses analyses of the ceramic layer under different load case by using the software ANSYS. Though these results, we find some relationships as follows:Only the hot load affects·In the ceramic layer, the stresses in X and Y direction have the obvious change along the irregular contact surface appearance. Moreover, the stresses extreme in two directions both appear in the appearance wave ridge apex or the trough apex.·Eliminating the appearance bulge part or the hollow part will change the distribution and the numerical value of the stresses in the two directions.·The appearance spacing and the appearance curvature are also two factors which have some relationships with the stresses of the two directions.·The existence of the appearances spires will cause the stress concentration near their locations in the ceramic layer. Both the hot load and the mechanical load simultaneously affect·The tensile stress in X direction distributes nearby the entire contact surface appearance, and achieves the maximum value in the appearance bulge parts. The compressed stress in X direction distributes far away from the contact surface, and the maximum compressed stress locate in the ceramic surface layer and its vicinity region. The stress in Y direction is nearly entirely in the compressed condition in the entire ceramic layer, and achieves the maximum value in the appearance bulge parts. And the tensile stress only appears in the appearance hollow part. ·In order to reduce the tensile stress in the vertical direction and the compressed stress in the horizontal direction, eliminate the appearance bulge part or the hollow part is advantageous for the service life without the influence of the spires.·The appearance spacing and the appearance curvature have differently influence on the stress in X and Y directions.It must be pointed that all the conclusions above are only qualitative reflection of the relation between the surface appearance and the stress in the thermal barrier coatings. Because we make the numerical simulation under a series of suppositional conditions. The influence of the surface appearance on the stress when the thermal barrier coatings withstand more complex load condition needs to be studied further.