Near-surface mechanical properties of KDP crystals in single point diamond turning

Indentation and single-point scratch tests are probably the simplest methods to measure the elastic, plastic and fracture behavior of brittle materials. Potassium Dihydrogen Phosphate (KDP) is a non-linear optical material used for laser frequency conversion and electrooptic modulators, it is typically machined by single point diamond turning. In this paper, in order to in-depth understand the near-surface mechanical properties of Potassium Dihydrogen Phosphate (KDP) crystals in diamond turning. The near-surface mechanical properties have been investigated include the plastic property, hardness H; the fracture property, fracture toughness K_c, and residual stress σ_r. Hardness of KDP crystals on (001) plane are examined under different loads, the influence of crystallographic orientation on hardness, fracture toughness and residual stress are also analyzed systematically. The results show that the hardness and fracture toughness have strongly anisotropy in different crystallographic orientations of the same crystal plane.