Determination of the mechanical properties of a composite material based on silicon nitride by the indentation method

DOI: 10.62564/M4-OL1324

Oleksandr Lukyanov, Svitlana Chugunova, Victor Melnyk, Iryna Goncharova

Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine


The purpose of the research was to determine the mechanical characteristics of silicon nitride ceramics and establishing optimal cutting regime of tool material. The composition (Si3N4+5%Al2O3+30%TiN) used for the manufacture of cutting tools were investigated. This composite was obtained by hot pressing of technical β-modification silicon nitride with an initial grain size of 0.6-1 μ with the addition of Al2O3 oxide to activate sintering and titanium nitride TiN in order to reduce the brittleness of the composite [1]. It was determine the following mechanical properties: Vickers hardness (HV), Knoop hardness (HK), fracture toughness K1C and plasticity characteristic δН. For brittle material, the use of the Knoop indenter allows to obtain high-quality indentation without chipping and cracks, which increases the accuracy of hardness measurement. To characterize the material's resistance to brittle fracture, the K1C value is used, which was determined by the indentation method based on the length of cracks that appear near the corners of the Vickers hardness indenter, and the value of δH was calculated from hardness measurements. The researched composite at room temperature has the following characteristics: HV=17,5GPa, НK=16,8GPa, K1С=8,35MN/m3/2, δН=0,52. To relieve internal stresses that are formed in ceramics during sintering due to different values of CTE (coefficient of thermal expansion) for Si3N4 and TiN, the composite was annealed at a temperature of 1050°C. After annealing, the mechanical characteristics remained at a fairly high level: HV=16GPa, НK=14GPa, K1С=7,4MN/m3/2, but δН increased to 0.55. Chipping of the edges of the cutting tool wasn’t observed. The research was carried out on the influence of cutting conditions on the mechanical characteristics of the tool. For hardened steel tools, the optimal regimes of cutting with silicon nitride ceramics were determined: t=0.02 mm, and S=0.5 mm/pass.

Keywords
Silicon nitride ceramics, fracture toughness, hardness, composite, mechanical characteristics

Acknowledgments
Not provided

References
[1] Gnesin G., Osipova I., Preparation and properties of tool materials based on silicon nitride, International Conference on Powder Metallurgy, Dresden, 1977, pp. 1-45 .