A physics-based life prediction methodology for thermal barrier coating systems

TL;DR

This paper introduces a physics-based, mechanistic method for predicting the lifespan of thermal barrier coating systems by integrating stress analysis, morphological data, and failure mechanisms within a continuum mechanics framework.

Contribution

It presents a novel life prediction methodology that combines statistical, non-destructive stress measurements with a detailed mechanical model accounting for material properties and oxidation effects.

Findings

The methodology accurately predicts TBC lifespan based on damage and stress data.

Calibration using fluorescence measurements aligns predictions with observed failures.

The approach is adaptable to various TBC types and thermal conditions.

Abstract

A novel mechanistic approach is proposed for the prediction of the life of thermal barrier coating (TBC) systems. The life prediction methodology is based on a criterion linked directly to the dominant failure mechanism. It relies on a statistical treatment of the TBC's morphological characteristics, non-destructive stress measurements and on a continuum mechanics framework to quantify the stresses that promote the nucleation and growth of microcracks within the TBC. The last of these accounts for the effects of TBC constituents' elasto-visco-plastic properties, the stiffening of the ceramic due to sintering and the oxidation at the interface between the thermally insulating yttria stabilized zirconia (YSZ) layer and the metallic bond coat. The mechanistic approach is used to investigate the effects on TBC life of the properties and morphology of the top YSZ coating, metallic low-pressure plasma sprayed bond coat and the thermally grown oxide. Its calibration is based on TBC damage inferred from non-destructive fluorescence measurements using piezo-spectroscopy and on the numerically predicted local TBC stresses responsible for the initiation of such damage. The potential applicability of the methodology to other types of TBC coatings and thermal loading conditions is also discussed.