An investigation of the mechanical properties and fracture characteristic of hot-pressed boron nitride ceramics


Ertug B., Boyraz T., Addemir O.

5th International Symposium on Nitrides, Eskişehir, Türkiye, 3 - 05 Nisan 2006, cilt.554, ss.201-202 identifier

Özet

The overall mechanical characterization of hot-pressed hexagonal boron nitride (h-BN) based ceramics was performed. Hardness, flexure strength and fracture toughness (K-IC) measurements were carried out using Vickers indentations, 3-point bending tests and SEVNB method, respectively. The fracture characteristics of hot-pressed h-BN ceramics were investigated by analyzing fracture surfaces using scanning electron microscope (SEM). The hardness, ranged from Hv = 0.20GPa to Hv = 0.25GPa, which was higher in the surfaces parallel to the hot-press direction due to the perpendicular alignment of the basal planes of the h-BN platelets to the hot-press direction. The fracture toughness and flexure strength values were determined to be 2.6 Wa.m(1/2) and 0.14 GPa, respectively. A single K-IC value was obtained since a slight variation of the fracture toughness was observed with the orientation of h-BN. The microstructural observations of h-BN grains indicated completely brittle fracture with intergranular voids and microcracks revealing a mixed mode of fracture.