Fabrication and properties of machinable 3Y–ZrO2/BN nanocomposites

3Y–ZrO2/BN ceramic composites with nano-sized BN dispersoids ranging from 0 to 30 vol.% were successfully fabricated by hot-pressing turbostratic BN (t-BN) coating 3Y–ZrO2 powders, which were prepared via in situ reaction between boric acid and urea on the surface of 3Y–ZrO2 particles in nitrogen gas. XRD analysis and TEM observations revealed that the nano-sized turbostratic and hexagonal BN (t/h-BN) particulates were dominantly dispersed at ZrO2 grain boundaries. Vickers hardness of materials decreased directly with an increase of BN content. The fracture strength and the fracture toughness were considerably improved, in comparison to corresponding 3Y–ZrO2/BN microcomposites. The nanocomposites with BN content more than 20 vol.% were ready for machining. The preliminary information on the relationship between microstructures and properties are provided.