Measurement of hardness on traditional ceramics

To reveal quantitatively the hardness of clayware and stoneware, Mohs, Vickers (micro and macro) and superficial Rockwell indentation measurements were applied to roofing tiles with different porosity. This work discusses the comparison of different indentation results, indentation size effect on porous clayware and the effect of microstructure on hardness of tiles. As a result, for Vickers indentation test, the critical indent load was found to 0.5 and 1 kg for soft and hard tiles, respectively, and indentation size/load effect (ISE) appeared clearly in hard tiles. The relationship between load (P) and indent size (d) on tiles was very close to a modified Myer’s law. The PSR (proportional specimen resistance) model gave P/d=0.67+0.02d, P/d=1.33+0.1d for soft and hard tiles, respectively. It was found that there were no difference in hardness of tiles mounted with epoxy or copper and as-received sample under superficial Rockwell indentation. These concepts on the harness evaluation of tiles would be applicable to other clayware.