Effect of structural parameters on the residual stress of Mo/8YSZ functionally graded thermal barrier coating prepared by plasma spraying

Abstract

In order to break through the technical bottleneck of traditional Mo/8YSZ double- layer thermal barrier coating which is easy to peel off at high temperature, the influence of the thickness of matrix, bonding layer, transition layer and ceramic layer on the residual stress of Mo/8YSZ functional gradient thermal barrier coating were studied. The numerical model of plasma spraying Mo/8YSZ functional gradient thermal barrier coating was established by using ANSYS finite element software. In the model, the variation of material thermal and physical parameters with temperature was considered, and the influence of different substrate, bonding layer, transition layer and ceramic layer thicknesses on the residual stress of functional gradient thermal barrier coating was analyzed. The results show that the maximum radial residual tensile stress and maximum radial residual compressive stress decrease with the increase of substrate thickness. With the increase of the thickness of bond layer, transition layer and ceramic layer, the maximum radial residual tensile stress increases and the maximum radial residual compressive stress decreases. Residual compressive stress is the main form of axial residual stress, with the increase of substrate thickness, maximum axial residual compressive stress of coating decreases, and with the increase of bonding layer or transition layer thickness, the maximum axial residual compressive stress increases, however, the change of ceramic layer thickness does not obviously effect the maximum axial residual compressive stress. The effect of changing the thickness of adhesive layer on the interface residual compressive stress is more obvious. The influence of the thickness of the matrix on the interface residual stress between the matrix and coating is within a certain range. When the substrate thickness increases to 12 mm, with the increase of the substrate thickness, the variation difference of the radial residual stress between the substrate and coating interface decreases. With the increase of the substrate thickness, the transition point and stress transition point of the stress form gradually transfer to the upper part of the boundary between the substrate and coating. With the increase of the thickness of the bonding layer, transition layer or ceramic layer, the transition point and stress transition point of the stress form gradually transfer to the lower part of the central area of the interface between the substrate and coating. By designing the functional gradient thermal barrier coating and adjusting the structural parameters of the thermal barrier coating system reasonably, the residual stress and stress mutation of the spraying component can be further reduced and the bonding strength between the substrate and coating can be improved.

Keywords

• plasma spraying
• functional gradient thermal barrier coating
• structural parameter
• thermal coupling
• numerical simulation