Effect of Microstructure on the Thermal Conductivity of Plasma Sprayed Y2O3 Stabilized Zirconia (8% YSZ)

Ningning Hu,Yi Zeng,Matiullah Khan,Yongzhe Wang,Chengkang Chang,Chucheng Lin,Xuemei Song

doi:10.3390/coatings7110198

Abstract

In this paper, the effect of microstructure on the thermal conductivity of plasma-sprayed Y2O3 stabilized ZrO2 (YSZ) thermal barrier coatings (TBCs) is investigated. Nine freestanding samples deposited on aluminum alloys are studied. Cross-section morphology such as pores, cracks, m-phase content, grain boundary density of the coated samples are examined by scanning electron microscopy (SEM) and electron back-scattered diffraction (EBSD). Multiple linear regressions are used to develop quantitative models that describe the relationship between the particle parameters, m-phase content and features of the microstructure such as porosity, crack-porosity, and the length density of small and big angle-cracks. Moreover, the relationship between the microstructure and thermal conductivity is investigated. Results reveal that the thermal conductivity of the coating is mainly determined by the microstructure and grain boundary density at room temperature (25 °C), and by the length density of big-angle-crack, monoclinic phase content and grain boundary density at high temperature (1200 °C).

Highlights

Yttria-stabilized zirconia (YSZ) is widely used to protect high-temperature components from corrosion and improve the operating temperature of gas-turbine engines
The ceramic powder used for the top coating was commercially available ZrO2–8 wt % Y2O3 and particle size of the raw material
The m-phase may be formed during the cooling process, and its content increases with increasing loss of yttrium due to vaporization during spraying at increasing particles’ temperature

Summary

Introduction

Yttria-stabilized zirconia (YSZ) is widely used to protect high-temperature components from corrosion and improve the operating temperature of gas-turbine engines. The main aim is to reduce the thermal conductivity of engine components by using YSZ material prepared by the atmospheric plasma spray (APS) method [1,2]. The spraying parameters and deposition efficiency in the plasma process produce a variety of microscopic defects, with pores and cracks appearing in the coatings [3,4,5]. These microscopic defects have great influence on the thermal conductivity of TBCs [6]. Some studies have investigated the relationship between the spray process and the microstructure of the thermal barrier coating.

Methods

Results

Conclusion