Crack Configuration beneath Vickers Indentation in Y2O3-Containing Tetragonal Zirconia Polycrystals

Crack configurations beneath Vickers indentations in 3mol% Y2O3-containing tetragonal zirconia polycrystals (Y-TZP) with grain sizes of 0.4μm (Z3Y-I) and 1.0μm (Z3Y-II) were measured using a stepwise polishing technique. The crack configuration beneath the Vickers indentation in Y-TZP was Palmquist type. The depth of the crack beneath the Vickers indentation in Z3Y-II was smaller than that of the crack in Z3Y-I. Upheaval was observed around Vickers and Knoop indentations, and on both sides of induced cracks. The height of the upheaval was about 2μm around the corner and the edge of the Vickers indentation. However, the height of the upheaval around the induced crack decreased progressively away from the indentation. The upheaval had a maximum value of about 2μm at the end of the minor axis in the Knoop indentation. However, the upheaval at the edge decreased linearly away from the minor axis and was zero at the end of the apse axis. No crack was induced beneath the Knoop indentation even if Y-TZP was indented using a load of 490N.