EFFECT OF GRINDING ON STRENGTH OF TETRAGONAL ZIRCONIA AND ZIRCONIA-TOUGHENED ALUMINA

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Abstract
The effect of grinding-induced damage, on the strength of a yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) and a zirconia-tough-ened alumina (ZTA) was investigated. The four-point flexure test was used to measure fracture strength as a function of grinding conditions. Flexure bar specimens were prepared by surface grinding transverse to the tensile stress direction in flexure testing. Two series of grinding experiments were performed. In the first series, four wheels with diamond particle sizes ranging from 25 to 180 μ,m were used to grind specimens at a fixed depth of cut. The strength of the Y-TZP decreased slightly with increasing diamond particle size. For ZTA the strength loss was increased as diamond particle size was increased. In the second series, one grinding wheel with a diamond particle size of 180 μm was used to grind specimens at a depth of cut per pass ranging from 2.5 to 100 μm. The Y-TZP showed a slight decrease in strength when the depth of cut was increased. However, for ZTA, the strength first decreased, then increased with increasing depth of cut. The grinding-induced subsurface damage, observed by a bonded-interface sectioning technique, consisted of cracks for ZTA, but no subsurface cracks could be found for Y-TZP. The effect of machining damage on the strength of ZTA was explained using the observed subsurface cracks and residual stresses that were measured using an indentation technique