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Micro-, submicro- and nano-Si3N4 - SiC composites sintered by the HPHT method

Klimczyk P., Urbanovich V.

Archives of Materials Science and Engineering

2009

Vol. 39, nr 2

92-96

Purpose: The purpose of the presented work is to study the influence of different Si3N4 and SiC powders on mechanical properties of Si3N4-SiC composites, to obtain a hard and tough engineering material, especially for cutting applications. Design/methodology/approach: Three kinds of Si3N4 - SiC composite, with initial powders of different grain size: micro-, submicro- and nano-structured, were sintered by the HPHT (High-Pressure High-Temperature) method. Several variants were made of each composite, with different Si3N4 to SiC phase volume ratios. The influence of grain size of the initial Si3N4 and SiC powders on mechanical properties of sintered materials was investigated. Density, Young's modulus, hardness and fracture toughness of composites were measured. Microstructural (SEM) investigations were also conducted for selected samples. Findings: A strong influence of initial powder size on mechanical properties of Si3N4 - SiC composites can be observed. Sintered materials obtained from submicron powders are characterized by better mechanical properties than those obtained from micro- and nanopowders. Research limitations/implications: The material obtained is characterized by a good combination of hardness and fracture toughness, but further improvement in toughness is possible by the addition of third phase dispersion particles to the Si3N4 - SiC system. Practical implications: A practical aspect of the research carried out is an improvement in mechanical properties of silicon nitride and silicon carbide-based composites. Following additional technical exploitation tests, the materials obtained could be used in cutting tools, various parts of machines and wear components. Originality/value: The composites obtained have a better combination of mechanical properties than comparable commercial materials.