Experimental and numerical investigation of heat generation and surface integrity of ZrO bioceramics in grinding process under MQL condition.

Zirconia bioceramics has tremendous potential in medical applications owing to biocompatibility and high mechanical properties. Meanwhile, thermal damage and surface defects limit the grindability to achieve the desired properties. Therefore, this research provides an investigation of various grinding parameters on heat generation and surface morphology using a diamond wheel. In addition, a triangular and parabolic moving heat flux is used for heat distribution analysis based on FEM-model. The parabolic model more corresponds to experimental compared to the triangular heat flux, with an average deviation of <5% and 6.5% under dry and MQL, respectively. The response surface methodology is applied to extract a statistical representation of inputs and outputs. Dry grinding temperature obtained in range of 200-540 °C, which by applying MQL, it decreased by 16-35%. Increasing cutting depth would worsen the MQL efficiency in force and temperature. Results indicate the impact of cutting depth on temperature and force is greatest, followed by the effect of feed-rate, and that of wheel speed is the least. Thus, the increasing feed-rate should be utilized to preserve the high removal rate. SEM images indicate material removal mechanism is accomplished by plastic and brittle mode. Furthermore, MQL and a combination of low depth of cut could effectively decline the surface roughness and defects formation by decreasing the brittle material removal mechanism in one step. MQL reduced surface roughness by 46% compared with dry grinding, so that its performance increase in higher cutting depth. Because at higher cutting depths, the MQL changes the prevailing chip removal mechanism from brittle to ductile-regime grinding.