Mechanical characterization of Si3N4-BN(pl) composites
authors Silva, RF; Carrapichano, JM; Oliveira, FJ
editors Vieira, T
nationality International
author keywords ceramic composites; fracture toughness; hardness; nitrides
keywords WEAR
abstract The solid lubrication properties of BN led to the development-of Si3N4-BN composites, aiming the production of self-lubricated high performance materials. Composites containing 10, 18 and 25vol% of hexagonal BN were hot-pressed at 1650degreesC, 25MPa. The microstructure was characterized by SEM, X-ray diffraction and stereologic image analysis. Vickers indentations were performed to evaluate hardness and indentation fracture toughness. The hardness ranged from Hv=12.9GPa to Hv=2.1 GPa with increasing BN amount. For a given amount of BN, hardness is higher in the surfaces parallel to the hot-pressing direction, as the basal planes of the BN platelets tend to align perpendicularly to this direction. The anisotropy in the microstructure also affects the values of K-IC, since the cracks deflect, aligning themselves with the platelets, or, in some cases, they cannot even propagate. When the propagation direction of the cracks is not perpendicular to the basal planes of the platelets, the fracture toughness does not change significantly with the amount or orientation of BN, having values between K-Ic=3.5MPa.m(1)/(2) and K-Ic=5.9MPa.m(1)/(2).
issn 1013-9826
isbn 0-87849-905-9
year published 2002
volume 230-2
beginning page 323
ending page 326
web of science category Materials Science, Ceramics; Materials Science, Composites
subject category Materials Science
unique article identifier WOS:000179553200074
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