Research On Surface Integrity Study Of Glass-Ceramic For Laser Gyro Mirror Substrate

The glass-ceramic with ultra-low thermal expansion coefficient is a critical optical material, it has good mechanical properties and chemical stability under high temperature, so it has been employed in the aerospace, exploration of space objects and a variety of key equipments in other advanced technologies. However, after ultra precision machining, the existence of surface affected layer, sub-surface damage and surface residual stress directly reduces the intensity of optical components, long-term stability, image quality, coating quality, and laser induced damage threshold and other important performance indicators. Therefore, accurate detection of surface integrity and comprehensive characterization to improve the quality of optical processing and processing efficiency is of great significance.This work studied surface integrity and sub-surface damage based on ultra-smooth surface of the glass-ceramic. Firstly, this work resorted to the indentation test to research the influence of affected layer on the contact stiffness, strain hardening exponent, indentation deformation distribution based on the theory of contact mechanics, and providing a viable characterization parameters to measure the depth of affected layer.Secondly, this work employed Nanoindentation system to discuss the surface residual stress, considering that the residual stress is sensitive to amount of material accumulate around the indentation under the pressure process, this work obtained the formula of residual stress by measuring the changes of indentation area. In terms of characteristics that the spherical indenter can produce a continuous strain, the yield stress and stress-strain curve were studied. Ultimately it has been obtained the variation of residual stress on the ultra-smooth surface of the glass-ceramic.Finally, this work explained the mechanism of sub-surface damage on the basis of indentation fracture mechanics, and the mode of polishing sub-surface damage was established. Then subsurface damage depth of polishing and lapping was measured by HF chemical etching. It achieved the accurate forecasting of sub-surface damage about optical materials by through discussing the radial crack depth mode and the mode between sub-surface damage depth and surface roughness (SSD ^SR^4/3 ratio mode). This work has been forecasted sub-surface damage depth from processing parameters and surface roughness...