Mechanical and tribological properties of hot-pressed h-BN/Si3N4 ceramic composites

h-BN/Si3N4 ceramic composites were fabricated by hot-pressing using sub-micrometer sized α-Si3N4, h-BN powders and Y2O3–Al2O3 sintering additives. The microstructural analysis indicated the growth of β-Si3N4 grains to be hindered by h-BN particles and the diameter and aspect ratio of elongated β-Si3N4 grains to decrease with increasing h-BN content. As expected, this increase of h-BN content resulted in a slight decrease in the bending strength and fracture toughness and a sharp decrease in the elastic modulus and Vickers hardness of h-BN/Si3N4 ceramic composites. In addition, the friction coefficient of the h-BN/Si3N4 ceramic composites decreased with increasing h-BN content. A spalling mode of failure has been observed on the worn surface of monolithic Si3N4 and 10 vol.%h-BN/Si3N4 ceramic composite.