Microstructure and Mechanical Properties of Hot Isostatically Pressed Whisker Reinforced Si3N4 Ceramics
Si3N4 ceramics reinforced with SiC or β-Si3N4 whiskers and formed by HIP using the ABB Cerama glass encapsulation process have been characterized by analytical electron microscopy and x-ray diffractometry. Additions of 2.5 wt% Y2O3 and 0.2 wt% Fe2O3 as metal oxide sintering additives had a significant influence on matrix microstructure and the mechanical properties of the composites. The metal oxides promoted the development of a fibrous matrix which increased room temperature strength and indentation fracture toughness. However, the residual intergranular glass in these materials reduced high temperature strength. Whiskers added together with the metal oxides did not have any significant influence on toughness, while an addition of whiskers to the equiaxed microstructure of material formed without the sintering additives had a clear toughening effect.
Unable to display preview. Download preview PDF.
- 2.Buljan S.T., Baldoni J.G. and Huckabee M.L., Si3N4-SiC Composites. Am. Cer. Soc. Bull., 1987, 66, 347–352.Google Scholar
- 3.Larker H.T. and Adlerbom J.E., Undoped and Low-doped Silicon Nitride with Whisker Reinforcement Made by Glass Encapsulated HIP. In Ceramic Materials and Components for Engines; Las Vegas, USA, Nov. 27-30, 1988, ed. V.J. Tennery, American Ceramic Society Inc., Westerville, Ohio, 1989, pp. 227–236.Google Scholar
- 6.Knutson-Wedel E.M., Falk L.K.L., Björklund H. and Ekstrom T., Si3N4 Ceramics Formed by HIP using Different Oxide Additions — Relation between Microstructure and Properties. Accepted for publication in J. Mater. Sci. Google Scholar
- 7.Lange F.F., Silicon nitride polyphase systems: fabrication, microstructure, and properties. Int. Met. Rev., 1980, No.1 Rev. 247, pp. 1–20.Google Scholar