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Testing hardness of technical ceramics. A new round robin

Ringversuch zur Härteprüfung an keramischen Werkstoffen
: Polzin, T.; Reich, T.; Ullner, C.

Materialprüfung 40 (1998), Nr.10, S.424-427
ISSN: 0025-5300
Fraunhofer IKTS ()
Oberflächenhärte; Aluminiumoxid; Zirkoniumdioxid; Siliciumoxid; Siliciumcarbid; Härteprüfung; VarianzAnalyse; Keramik; Ringversuch

A round robin has been conducted by 10 laboratories on testing the Knoop hardness of several commercial advanced technical ceramics. The results were analyzed by means of three models the first of which is able to find out what material could be used for reference. The second allows to separate the variances caused by certain specimen, by indentation, and by observing or measuring. The third model evaluates the experimental quality of the participating laboratories. Microcracking, cavities, and inhomogeneity of ceramic materials have an important influence on the hardness test results. Scattering caused by the equipment and by the operators is negligible compared to that by the ceramics. The Knoop hardness can be used to characterize technical ceramics. Reference materials require a homogenouos fine grain structure and high density. None of the tested materials is appropriate and fulfil these requirements.