研究了磷酸二氢钾(KDP)晶体表面典型缺陷的形成原因及抑制方法。通过飞切加工及表面染色切削实验证明了成因分析结果的正确性,进一步明确了KDP晶体表面缺陷的形成过程。建立了适用于描述KDP晶体表面缺陷形成过程的理论模型,提出了获得无缺陷晶体表面的工艺条件。对飞切加工参数及刀具结构进行了优化,实验验证了缺陷抑制措施的有效性。研究结果表明,在飞切条件下,KDP晶体(001)晶面的脆塑转变(BDT)深度变化范围为125~268 nm,当沿45°方向切削时BDT深度最大,此时只要保证进给速率小于36.6 μm/r即可避免在晶体表面形成凹坑。通过优化刀具结构,可消除晶体表面的凸起缺陷,有效抑制KDP晶体的表面缺陷,最终获得了粗糙度小于2 nm的光滑KDP晶体表面。

The formation reasons and suppression methods of the typical defects generated on the surface of the potassium dihydrogen phosphate (KDP) crystal are investigated. The correctness of the analysis results of the formation reasons are 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 are further clarified. Theoretical models which are suitable for the description of the formation process of the surface defects of the KDP crystal are established and the process conditions for the realization of the defect-free KDP surfaces are shown. The fly-cutting fabrication parameters and the cutting tool structures are 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° 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 μm·r -1. Besides, the convex defects are 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.