Title: Colour variations in silicon nitride

Authors: R. Westergard, G. Akdogan, N. Axen

Addresses: Uppsala University, The Angstrom Laboratory, Box 534, S-751 21 Uppsala, Sweden. University of the Witswatersrand, School of Process and Materials, Engineering, 2050 Johannesburg, South Africa

Abstract: Silicone nitride is a general-purpose structural ceramic material used for example in gas turbines, bearings, seals and various wear parts. After densification of silicon nitride with sintering additives, variations in the colour or nuance occasionally appear on the material. To investigate the origin of the colour variations, differently coloured hot-isostatically pressed silicone nitrides with yttria additives were analysed with respect to composition, microstructure, hardness, fracture toughness and wear resistance. The results suggest that the differences in colour originate from the degree of crystallinity of the intergranular silicate phase. The colour variations were also accompanied by differences in the mechanical properties.

Keywords: discolouration; intergranular phase; silicon nitride; sintering aids; wear.

DOI: 10.1504/IJMPT.2001.001293

International Journal of Materials and Product Technology, 2001 Vol.16 No.8, pp.736-744

Published online: 02 Jul 2003 *

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