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Why can heat generated by wear cause thermal shock in ceramics?

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advanced structural ceramics Figure 1: Resistance to cracking in transformation-toughened zirconia. In a ceramic composed of tetragonal zirconia dispersed in a zirconia matrix, the stress field advancing ahead of a propagating crack transforms the small tetragonal particles to larger monoclinic particles. The larger particles exert a crack-closing force in the process zone behind the crack tip, effectively resisting propagation of the crack.

Thermal shock in ceramics is primarily caused by rapid temperature changes that induce internal stress, rather than heat generated by wear itself. While wear can generate localized heat, thermal shock occurs when an object experiences a sudden temperature gradient—typically during rapid cooling—causing the surface layers to contract or expand at a different rate than the inner layers.12

This differential volume change creates significant tensile stress within the material. Because ceramics are inherently brittle and possess high flaw sensitivity, they are susceptible to these stresses, which can lead to the propagation of cracks and potential structural failure.123

To mitigate this, engineers often adjust the microstructure of structural ceramics during processing. By incorporating porosity or specific grain sizes, the material can better blunt advancing cracks, thereby reducing its susceptibility to thermal shock. It is important to note that while ceramics are valued for their robustness in high-temperature environments, their brittleness remains a critical challenge that must be managed through advanced engineering techniques.13