Abstract: During the precision grinding of sapphire, some defects such as cracks, micro fractures, dislocations are prone to generate on the surface, and residual tensile stress will occur on the surface, this has adverse effects on subsequent proces sing and performance. In this study, thermal repairing method is used to repair the grinded sapphire surface. Under the conditions of different thermal repairing temperature, holding time and cooling rate, thermal repairing test is carried out on sapphire A -plane, C-plane, M-plane and R-plane using argon gas as shielding gas. Experimental results show that thermal repairing can effectively reduce the surface residual tensile stress, improve the surface lattice integrity, and the largest residual stress reduction rate can reach 53% when the thermal repairing temperature is 1 500℃. With the increase of thermal repairing temperature and holding time, the residual tensile stress of sapphire grinding surface decreases and the surface lattice integrity is improved. With the in crease of cooling rate, the reduction rate of surface residual tensile stress decreases, and the thermal repairing effect is weakened. Among sapphire with different crystal orientations, R-plane sapphire surface has the largest reduction rate of residual stress after thermal repairing. In thermal repairing of polished sapphires, the atomic step morphology after surface atoms rearrangement is observed. Thermal repairing is proved to be an effective method of low damage processing of sapphire.

Key words: grinding, sapphire, thermal repairing characteristics, surface properties, residual stress