engleski

Influenece of Surface Roughness of Alumina Ceramics on Indentation Size

Alumina (Al2O3) is one of the most important technical ceramic materials, due to its good properties and acceptable price. For some purposes, it is important to achieve either very smooth or rough surface of the ceramic object. The aim of this study was to evaluate the influence of different surface finish processes on the surface roughness of alumina and, consequently, on the measured Knoop hardness. Four types of samples were prepared, each with the different surface finish – ground with different SiC abrasive papers or polished with diamond pastes with different granulation. On each sample three indentation loads were used: 0.4903 N (HK 0.05), 4.903 N (HK 0.5) and 49.03 N (HK 5). It has been noticed that all samples exhibited a decrease in hardness with the increasing applied test load, a phenomenon known as the normal indentation size effect (ISE). In order to evaluate this occurrence, three mathematical models were applied – Meyer’s law, proportional specimen resistance (PSR) and modified proportional specimen resistance (MPSR) model. Obtained results showed that the alumina surface roughness significantly affects the measured Knoop hardness. Dependence of Knoop hardness and the indentation load can be quantified using all three mathematical models.

alumina ceramics ; Knoop hardness ; surface roughness ; indentation size effect

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