Ultra-precision grinding of Gd3Ga5O12 crystals with graphene oxide coolant: Material deformation mechanism and performance evaluation

Abstract

• GO lubrication assisted grinding was innovatively applied in crack-free machining of GGG crystals. • Plastic deformation of GGG induced by GO assisted grinding was dominated by polycrystallization nanocrystals and amorphous transformation. • Interlayer slip and filling actions of GO significantly affect the deformation and removal processes of GGG crystals. • Compared with conventional grinding, surface roughness and friction coefficient of GO assisted grinding were effectively reduced. Laser crystals of rare-earth oxide are primary host materials for making solid-state lasers of large power. However, brittle fractures and cracks are easily formed on the crystal’s surface and subsurface during abrasive machining process owing to their high hardness and brittleness, which will seriously reduce output power of the lasers. In this work, a grinding coolant was synthesized through dispersing GO nanosheets in water, and the grinding experiment of GGG laser crystals assisted by GO coolant lubrication was systematically performed. The plastic deformation mechanism of GGG crystals induced by GO assisted grinding was revealed at close-to-atomic scale by Raman spectrum and cross-section TEM detection technologies. The results indicated that the plastic deformation of GGG crystals during GO assisted grinding was affected by the interlayer slip and filling actions of GO, and was dominated by polycrystallization nanocrystals and amorphous transformation caused by the crystal plane slipping. The use of the GO coolant enabled to lower friction at the abrasive-substrate interface significantly owing to their self-lubricating effect, thus resulting in improved ground surface quality, in comparison with conventional grinding. This work will provide a new theoretical basis and technical support for high-efficiency and low-damage ultra-precision grinding of laser crystals.