Methods for Surface Defect Suppression in Fly-Cutting Fabrication of KDP Crystals

The formation reasons and suppression methods of the typical defects generated on the surface of the potassium dihydrogen phosphate (KDP) crystal arc investigated. The correctness of the analysis results of the formation reasons arc confirmed via the fly-cutting fabrication and the surface painting fly-cutting experiments, and the formation process of the surface defects of the KDP crystal arc further clarified. Theoretical models which arc suitable for the description of the formation process of the surface defects of the KDP crystal arc established and the process conditions for the realization of the defect-free KDP surfaces arc shown. The fly-cutting fabrication parameters and the cutting tool structures arc optimized, and thus the validity of the suppression methods is verified. The research results show that, the variance range of the brittle ductile transition (BDT) depth of the (001) plane of KDP crystal is 125-268 nm under the fly-cutting conditions. When the cutting is along 45 degrees direction, the BDT depth reaches the maximum. At this point, the fracture pits can be avoided on the crystal surface as long as the feed rate does not exceed 36.6 mu m.r(-1). Besides, the convex defects arc eliminated by the optimization of the cutting tool structures, the surface defects of the KDP crystal can also be suppressed effectively, and thus a smooth KDP surface with a roughness less than 2 nm is obtained.