Microstructure and Mechanical Properties of Si₃N₄-Fe₃Si Composites Prepared by Gas-Pressure Sintering.

Jiasuo Guan,Laifei Cheng,Mingxing Li

doi:10.3390/ma11071206

Jiasuo Guan, Laifei Cheng + Show 1 more

Open Access

https://doi.org/10.3390/ma11071206

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Journal: Materials	Publication Date: Jul 13, 2018
Citations: 3	License type: CC BY 4.0

Affiliation: Northwestern Polytechnical University

Abstract

Si3N4-Fe3Si composites were prepared using Fe-Si3N4 as the source of Fe3Si by gas-pressure sintering. By adding different amounts of Fe-Si3N4 into the starting powders, Si3N4-Fe3Si composites with various Fe3Si phase contents were obtained. The microstructure and mechanical properties of the composites were investigated. With the increase of Fe-Si3N4 contents, the content and particle size of Fe3Si both increased. When more than 60 wt. % Fe-Si3N4 were added, the abnormal growth of Fe3Si particles occurred and oversized Fe3Si particles appeared, leading to non-uniform microstructures and worse mechanical properties of the composites. It has been found that Fe3Si particles could toughen the composites through particle pull-out, interface debonding, crack deflection, and particle bridging. Uniform microstructure and improved mechanical properties (flexural strength of 354 MPa and fracture toughness of 8.4 MPa·m1/2) can be achieved for FSN40.

Highlights

Si3 N4 is one of the most promising engineering ceramics with high strength, high hardness, good oxidation, and corrosion resistance—even at high temperature
It can be found that the dense ceramic composites with high densities (≥3.2 g/cm3 ) and low open porosities (≤2.06%)
Si3 N4 -Fe3 Si composites with a different content of the Fe3 Si phase were fabricated using starting powders of different compositions

Summary

Introduction

Si3 N4 is one of the most promising engineering ceramics with high strength, high hardness, good oxidation, and corrosion resistance—even at high temperature. It is an irreplaceable material in modern industries [1,2,3,4]. In some price-sensitive areas, like the Metallurgical industry, the cost of Si3 N4 is still too high. To tackle this problem, a novel refractory material, ferro-silicon nitride (Fe-Si3 N4 ) has been developed and has successfully replaced the relatively expensive Si3 N4 [5,6]. Using the ferro-silicon alloy FeSi75 as the raw material, Fe-Si3 N4 powder can be synthesized by direct nitridation [7,8,9] or self-propagating high-temperature synthesis [10,11,12,13] under nitrogen atmosphere

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