An investigation on the nano-abrasion wear mechanisms of KDP crystals

Potassium dihydrogen phosphate (KDP) is an important material in the optics industry due to its excellent physical and optical properties. It is also a difficult-to-process material due to its brittleness and sensitivity to environment and external stresses such as contact sliding stresses, temperature variation and humidity change. This paper presents the first investigation into the nano-abrasion wear mechanisms of KDP using molecular dynamics (MD) analysis. Nanoscratching simulations were conducted with various scratching depths in various crystallographic orientations. It was found that the deformation mechanisms of KDP under nano-abrasion are greatly affected by the anisotropy of the material. The nano-abrasion on the (001) surface experiences the least resistance of material removal. The elastic recovery on the (100) surface is greater than that on the (001) surface. The coefficient of friction increases with increasing the scratching depth, and reaches the highest on the (001) surface. Different phase transformations emerge under contact stresses. The study revealed that the phase transformations are initiated under corresponding critical hydrostatic stresses with high shear stress.