Damage analysis: Ceramics

Technical ceramics are generally used where other construction materials such as metals and plastics reach their limits under severe application conditions, especially under mechanically demanding applications at high temperatures and/or when withstanding chemically aggressive situations.

Although ceramic materials are harder, stronger and more corrosion and wear resistant than polymers and metals, they may also cause problems due to their low damage tolerance. This can even lead to complete failure of ceramic components. A comprehensive analysis of the causes may then help both in preventing future failures as well as in minimizing the risk of failure in the first place by choosing appropriate materials and through component testing.

As with all material groups, the causes of failure are varied and can be mostly attributed to overlapping load conditions. However, these causes within the varied material groups need to be properly assessed. Evaluating ceramic components and the causes for their failure requires a particular focus upon material quality (microstructure, surface finish). Moreover, long-term damage caused by cyclic loading or corrosive attack needs to be analyzed.

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Methods

For the assessment of component damage, the exact knowledge of the working conditions is critically important. This allows both taking into account as well as the exclusion of specific causes, and thus leads to a more rapid clarification of the failure.

Most important methodologies:

• Standard methods of light and laser microscopy and ceramography to identity and assess failure origins.
• High-resolution scanning electron microscopy with connected elemental analysis to detect microstructural effects and corrosive damage.
• Vibrational spectroscopy (FTIR, Micro-Raman spectroscopy) to analyze and quantify chemical reaction products and microstructural changes like phase transitions.
• Surface analyses such as hardness and roughness measurement, wettability.

If required, it is possible to include mechanical and thermal testing of materials and components to assess the load limits of these components under specific application conditions. In addition, various simulation techniques are available to identify stresses under critical loading conditions and for determining the risk of ceramic component failure.

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