Critical cutting thickness model considering subsurface damage of zirconia grinding and friction–wear performance evaluation applied in simulated oral environment

Abstract

Ductile mode removal is always a popular topic in zirconia ceramic cutting and grinding. The completely undamaged ductile mode grinding is extremely inefficient and difficult to control, which limits the clinical application of dental zirconia ceramics. Hence, considering the effect of subsurface damage, this paper redefines the ductile mode grinding removal of ceramic materials and establishes a critical cutting thickness model for zirconia ceramic grinding. Results show that the better the lubrication condition, the smaller the subsurface damage degree and the larger the removal range of ductile zone. To verify the model, grinding experiments of zirconia ceramic under different lubrication conditions are conducted. The results show that grinding under nanofluid minimum quantity lubrication obtains the lowest friction coefficient, which is reduced by 58.54 % and 18 % compared with dry grinding and minimum quantity lubrication (MQL), respectively. Under nanofluid minimum quantity lubrication (NMQL) condition, the critical cutting thickness is 2.27 µm, which is 160.92 % larger than that under dry grinding. The error between the theoretical model and the experimental results is 10.67 %, which verifies the correctness of the theoretical model. Furthermore, using the workpiece material obtained from grinding experiments, friction–wear experiments are conducted on dental zirconia ceramics under different loads in a simulated oral environment. The results show that zirconia ceramics obtained by NMQL grinding achieve better anti-friction and anti-wear performance than that of MQL. When the maximum cutting thickness of zirconia ceramics processed by NMQL grinding is 2.27 µm, the wear rate of the workpiece is 3.06 × 10−5 mm3/N·m, and at 2.6418 µm, the wear rate of the workpiece is 2.01 × 10−3 mm3/N·m. This paper aims to provide theoretical guidance and technical support for the ductile mode removal of hard, brittle materials.