Comprehensive damage evaluation of localized spallation of thermal barrier coatings

Abstract

Thermal barrier coatings (TBCs) enable the hot section part to work at high temperatures owing to their thermal barrier effect on the base metal components. However, localized spallation in the ceramic top-coat might occur after long duration of thermal exposure or thermal cycling. To comprehensively understand the damage of the top-coat on the overall hot section part, effects of diameter and tilt angle of the spallation on the temperature redistribution of the substrate and the top-coat were investigated. The results show that the spallation diameter and tilt angle both have a significant effect on the temperature redistribution of the top-coat and the substrate. In the case of the substrate, the maximum temperature increment is located at the spallation center. Meanwhile, the surface (depth) maximum temperature increment, having nothing to do with the tilt angle, increases with the increase of the spallation diameter. In contrast, in the case of the top-coat, the maximum temperature increment was located at the sharp corner of the spallation area, and the surface (depth) maximum temperature increment increases with the increase of both the spallation diameter and the tilt angle. Based on the temperature redistribution of the substrate and the top-coat affected by the partial spallation, it is possible to evaluate the damage effect of spalled areas on the thermal capability of TBCs.

Phase Composition, Thermal Conductivity, and Toughness of TiO2-Doped, Er2O3-Stabilized ZrO2 for Thermal Barrier Coating Applications

“…Up to now, the most widely used TBCs are made of 7-8 wt.% Y 2 O 3 -stabilized ZrO 2 (YSZ), due to its low thermal conductivity, good phase stability, large thermal expansion, and desirable fracture toughness [1][2][3][4]. The primary methods to produce TBCs are electron beam physical vapor deposition (EB-PVD), air plasma spraying (APS), and plasma spray physical vapor deposition (PS-PVD) [1,2,[5][6][7].…”

Potential thermal barrier coating materials: RE3NbO7 (RE=La, Nd, Sm, Eu, Gd, Dy) ceramics

“…YSZ exhibits relatively low thermal conductivity (2.1‐3.0 W m −1 K −1 , 25‐1000°C), high thermal expansion coefficients (10.0 × 10 −6 K −1 , 1200°C), excellent high‐temperature toughness and low Young's modulus . Nevertheless, the application temperature of YSZ is below 1200°C as the phase transition over 1200°C will lead to volume expansion and then fail the coatings . Furthermore, high sintering rate of YSZ will cause the increase of Young's modulus and thermal conductivity .…”

Oxygen‐vacancy‐mediated microstructure and thermophysical properties in Zr3Ln4O12 for high‐temperature applications

“…In brief, increasing of the rare‐earth oxide alloying concentration, from YSZ to 2ZrO 2 –Ln 2 O 3 , considerably reduces the thermal conductivity due to the accompanying oxygen vacancies. However, high concentration of “mobile oxygen vacancies” with high mobility increases the oxygen diffusion through the coating during high temperature operations, resulting in a rapid thickening of the thermally grown oxide (TGO) layer between the topcoat and bondcoat . Moreover, grain coarsening and pore sintering within ceramic coatings are also simultaneously enhanced.…”