Influence of interface morphology of transition layer on the residual stresses of plasma sprayed ZrC-based coatings examined by finite element simulations

The influence of the interface morphology of the SiC transition layer, including the shape, roughness and curvature, on the residual stresses of plasma sprayed ZrC-based coatings was simulated and analyzed in the current work. The results indicated that when the valleys and peaks of the interface were removed from the sine wave interface of the transition layer, the maximum values of radial compressive stress and axial tensile stress in the coating have transferred from the peak to the flat valley zone. An abrupt shear stress was found at the peaks and valleys, and a stress gradient was observed at the interface, making it easy to induce cracks perpendicular to the interface. Tensile stress concentration was located at the edge of the coating sample, where a large stress gradient was generated, resulting in easy cracking at the edge of the coating. The transition layer interface of the sine wave with valley-only morphology reduced the residual stress and improved the bonding strength of the interface, which was considered to be the optimal interface. The radial compressive stress and axial tensile stress in the coating increased with increasing interfacial curvature, with more significant changes observed for the axial tensile stress. This will lead to easy cracking and spalling of the coating, which was confirmed by experimental results. When the curvature of the interface is in the range of [0.2,0.3], the coating and substrate have good interface bonding strength.