Study on Stress Development in the Phase Transition Layer of Thermal Barrier Coatings.

Yijun Chai,Yueming Li,Xian Wang,Chen Lin

doi:10.3390/ma9090773

Abstract

Stress development is one of the significant factors leading to the failure of thermal barrier coating (TBC) systems. In this work, stress development in the two phase mixed zone named phase transition layer (PTL), which grows between the thermally grown oxide (TGO) and the bond coat (BC), is investigated by using two different homogenization models. A constitutive equation of the PTL based on the Reuss model is proposed to study the stresses in the PTL. The stresses computed with the proposed constitutive equation are compared with those obtained with Voigt model-based equation in detail. The stresses based on the Voigt model are slightly higher than those based on the Reuss model. Finally, a further study is carried out to explore the influence of phase transition proportions on the stress difference caused by homogenization models. Results show that the stress difference becomes more evident with the increase of the PTL thickness ratio in the TGO.

Highlights

A thermal barrier coating system (TBCs) is highly advanced material system, mainly applied to the metallic surfaces of gas-turbine engines
As the oxygen diffuses through the Top Coat (TC), the bond coat (BC) materials are gradually oxidized to thermally grown oxide (TGO)
Numerical calculations have been subroutine in finite element ABAQUS code is developed

Summary

Introduction

A thermal barrier coating system (TBCs) is highly advanced material system, mainly applied to the metallic surfaces of gas-turbine engines. These coatings provide heat insulation to the metallic parts from the extremely hot gas steam [1,2,3,4], and allow the engines to work at higher operating temperatures, which could significantly improve the turbine efficiency [5,6]. Due to the large and prolonged heat loads, much attention should be paid to the high-temperature mechanical performance of the TBC materials system, especially the high-temperature oxidation behavior, which could reduce the TBC life drastically and lead to thermal fatigue. As the oxygen diffuses through the TC, the BC materials are gradually oxidized to thermally grown oxide (TGO)

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Results

Conclusion