THE INFLUENCE OF DIAMOND GRINDING MODES ON THE PHASE COMPOSITION AND CRACK RESISTANCE OF ZIRCONIA-BASED CERAMICS

The influence of diamond grinding modes on the structure and mechanical properties of ceramics based on zirconium dioxide stabilized with magnesium oxide has been studied. Powders of the composition ZrO2 – 6 mol. % MgO was obtained by chemical co-precipitation from solutions of zirconium and magnesium chloride salts. The blanks of the samples were made by cold isostatic pressing at maximum pressures of 55 and 200 MPa, followed by sintering at a temperature of 1700 ?C for 4 hours. The resulting blanks (both porous and high-density) were machined with different cutting depths in the range of 0.003…0.010 mm. It was found that the surface roughness of the samples increased with increasing cutting depth. After mechanical processing of high-density samples obtained at a maximum pressure of 200 MPa, conditions are created on their surface for the implementation of a phase transition. Grinding promotes the transition of the tetragonal phase of zirconium dioxide (t-ZrO2) to the monoclinic phase (m-ZrO2) on the surface of the samples, which leads to an increase in the critical stress intensity coefficient (K1c) from 4.3 to 6.4 MPa·m1/2. Mechanical processing of samples with an open porosity of 3.0…3.5 % obtained by pressing at a maximum pressure of 55 MPa does not lead to phase transformations on their surface and K1c remains within the margin of error.