Normalized evaluation of thermal shock resistance for ceramic materials

Kai Li,Lucun Guo,Dalei Wang,Han Chen

doi:10.1007/s40145-014-0118-9

Kai Li, Lucun Guo + Show 2 more

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https://doi.org/10.1007/s40145-014-0118-9

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Abstract

A normalized method for evaluation of thermal shock resistance for ceramic materials was proposed. A thermal shock resistance index (TSRI), Г, in the range of 1 to 100, was introduced, based on a normalized formula obtained directly by a simple testing process of determining the changes in flexural strength before and after thermal shock cycles. Alumina ceramic was chosen as the model material and its thermal shock behavior was investigated systematically by water quenching. Based on the experiments on alumina ceramic, the thermal shock behaviors of other 19 types of ceramic materials ranging from porcelain, refractory ceramics to advanced ceramics including structural and functional ceramics were also evaluated, and their TSRIs, Г, were derived. The dependence of Г on the coefficient of thermal expansion (CTE) of the materials was plotted, and it revealed that CTE is the most critical factor in affecting the thermal shock resistance for various ceramic materials. The effect of other factors such as porosity and fracture toughness on the index was also discussed.

Highlights

Ceramic materials are widely used in various fields of engineering because of their many excellent properties such as high hardness, high melting points, resistance against oxidation and chemical corrosion, and high-temperature stability [1,2,3]
The thermal shock resistance provides a measure of the ability of ceramic materials to withstand thermal stresses and thermal shock failure when they are subjected to rapid changes in temperature [4,6]
Subjected to repeated thermal shock may be attributed to only subcritical microcrack initiation or propagation as increasing number of cycles, because the formed large cracks in the body of alumina ceramic give a necessary space for accommodating thermal stresses as indicated by pronounced R-curve behavior [18]

Summary

Introduction

Ceramic materials are widely used in various fields of engineering because of their many excellent properties such as high hardness, high melting points, resistance against oxidation and chemical corrosion, and high-temperature stability [1,2,3]. The evaluation parameter R derived by Hasselman was given in the following equation [16]: Both theories indicate that the factors affecting thermal shock resistance of ceramic materials are a complex function of the coefficient of thermal expansion, flexural strength, elastic properties and thermal conductivity. An evaluation parameter in the European Standard is the critical temperature difference determined at which fracture is just initiated, or at which there is a first drop in mean strength by more than 30% of the initial mean strength [27] These evaluating methods are time-consuming, and have limited ability to clearly distinguish among different levels of thermal shock resistance for a wide range of ceramic materials with a manner of quantification. We report a normalized method based on the introducing index for evaluation of thermal shock resistance of various ceramic materials

Experimental procedures

Results and discussion

Conclusions