Thermal Conductivity of Multi-Sized Porous Thermal Barrier Coatings at Micro and Nano Scales after Long-Term Service at High Temperatures

Pei-Hu Gao,Lu Jia,Bai-Yang Chen,Jian-Ping Li,Yong-Chun Guo,Can Jin,Quan-Ping Li,Yong-Qing Lu,Zhong Yang,Min-Xian Liang,Sheng-Cong Zeng,Bo Zhang,Dan Zhao

doi:10.3390/coatings11101183

Abstract

Thermal barrier coatings with multi-sized porous structure at micro and nano scales were prepared with hollow spherical YSZ powders and polypropylene powders through atmospheric plasma spraying. The thermal conductivities of the multi-sized thermal barrier coatings after a long-term serving at high temperature were tested through laser flash heating method. Meanwhile, the physical models of thermal barrier coatings with multi-sized porous structure at micro and nano scales were constructed through Ansys Workbench. The evolutions of thermal conductivity of thermal barrier coatings with multi-sized pores after long-term service at 1100 °C were investigated through computation. It was found that the thermal conductivity of the coating increased with the extension of the serving time. When the serving time reached 60 days, the thermal conductivity of the coating tended to be stable and close to the compacted bulk. The computational results were consistent with the tested ones, which could be helpful to explain the thermal conducting evolution in thermal barrier coatings with multi-sized porous structure at nano and micro scales after long-term serving at high temperature.

Highlights

Thermal barrier coatings (TBCs) have been widely used in hot sections of advanced gas turbines and aeroengines to improve the reliability and durability as well as the efficiency of engines [1,2,3]
The thermal conductivity of the TBCs increased with the increase of the serving times
The nano-sized pores would disappear during the serving at high temperature, which would lead to the increase of the thermal conductivity in the multi-sized porous TBCs

Summary

Introduction

Thermal barrier coatings (TBCs) have been widely used in hot sections of advanced gas turbines and aeroengines to improve the reliability and durability as well as the efficiency of engines [1,2,3]. It is necessary to investigate the thermal conductivity evolution of thermal barrier coatings with multi-sized porous structure at nano and micro scales after serving at high temperature for a long-term. The real multi-sized porous TBCs were prepared through atmospheric plasma spraying with hollow spherical YSZ powders and polypropylene powders as pore forming agent. The evolution of the thermal conductivity in TBCs with multi-sized pores after a long-term serving at high temperature were simulated through Ansys and tested through laser flash heating method, respectively. The appropriate simulation model was based on the SEM-images and idealized to simple three directional distribution with the same ratio of each sized pores and total porositiesas the real TBCs. the thickness of TGO was adjusted to the serving times according to the real thickness evolutions of the TGO during the long-term serving at high temperature. Ressaumlptsle (kg·m−3) (The Archimedes drainage method is used to measure the density)

Microstructure of the Deposited Porous TBCs

Thermal Conductivity Computation of Porous TBCs after Long Time Serving

Thermal Conductivity of the Multi-Sized Porous TBCs after Long-T Temperature

Conclusions