蓝宝石精密磨削表层热修复特性研究

Research on Thermal Repairing Characteristics of Sapphire Precision Grinding Surface

蓝宝石精密磨削过程中易产生表面裂纹、微观断裂、位错等缺陷,同时也会产生残余拉应力,对后续加工及性能发挥产生不良影响。采用热修复方法对磨削后蓝宝石表层进行处理,以氩气作为保护气,在不同热修复温度、保温时间以及降温速度等条件下,对A、C、R、M面的蓝宝石晶体进行热修复试验。结果表明,热修复方法能够有效降低表面残余拉应力,同时提升表面晶格完整性,其中热修复温度1500℃时残余拉应力降幅最高,可达53%;随着热修复温度的增加以及热修复时间的增长,蓝宝石磨削表面残余应力逐渐降低,而且表面晶格完整性变好;随着降温速度增加,表面残余拉应力的降幅减小,热修复效果减弱;在不同晶向的蓝宝石中,R面蓝宝石热修复后表面残余拉应力降幅最大;通过对抛光后蓝宝石进行热修复,观察到了表层原子重新排列的台阶结构。证实热修复方法为蓝宝石的低损伤加工提供了一种有效方法。

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 processing 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 1500℃.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 increase 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.