Influence of Diamond Grinding Modes on the Phase Composition and Crack Resistance of Zirconia-Based Ceramics

Abstract

The influence of diamond grinding modes on the structure and mechanical properties of ceramics based on zirconium dioxide stabilized with magnesium oxide was studied. Powders of the ZrO₂ – 6 mol.% MgO composition were obtained by chemical coprecipitation from solutions of zirconium and magnesium chloride salts. The powders were pressed into specimens by cold isostatic pressing at maximum pressures of 55 and 200 MPa, followed by sintering at a temperature of 1700°C for 4 h. The resulting — both porous and high-density — specimens were machined at different cutting depths in the range of 0.003 – 0.010 mm. The surface roughness of the specimens was found to increase with an increase in the cutting depth. The machining of high-density specimens obtained at the maximum pressure of 200 MPa was established to create conditions for the implementation of a phase transition on their surface. Grinding facilitates the transition of the tetragonal phase of zirconium dioxide (t-ZrO₂) to a monoclinic phase (m-ZrO₂) on the surface of the specimens, which leads to an increase in the critical stress intensity factor (K_Ic) from 4.3 to 6.4 MPa · m^1/2. Machining of the specimens with an open porosity of 3.0 – 3.5% obtained by pressing at the maximum pressure of 55 MPa did not lead to phase transformations on their surface, with K_Ic remaining within the margin of error.