Scratch resistance of sodium borosilicate glass

Abstract

Scratch resistance of sodium borosilicate glasses (20Na2O·80(1 - x)SiO2·40xB2O3 x = 0, 0.2, 0.4, 0.6, 0.8, 1) was investigated by using a Knoop indenter. In addition, Vickers hardness, Young's modulus, and fracture toughness were measured and their compositional variations were compared. It was found that the scratch hardness test was a simple and useful method for evaluating the mechanical failure in glass. The maximum Vickers hardness, 4.2 GPa, and Young's modulus, 84 GPa, were obtained at the composition of x = 0.4. It is considered that this compositional dependence is related with the fractions of four- and three- coordinated boron atoms. On the other hand, scratch hardness and fracture toughness decreased monotonically with the increase of x. This result indicates that both scratch resistance and fracture toughness are associated not only with the energy of the fracturing bonds, but also with energy dissipating processes, such as plastic deformation. Under the present testing condition, scratch hardness rather reflects the fracture mechanism than the elastic behavior.