Effect of in situ VSi2 and SiC phases on the sintering behavior and the mechanical properties of HfB2-based composites

Soheil Ghadami,Farzin Ghadami,Ehsan Taheri-Nassaj,Hamid Reza Baharvandi

doi:10.1038/s41598-020-73295-7

Soheil Ghadami, Farzin Ghadami + Show 2 more

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https://doi.org/10.1038/s41598-020-73295-7

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Abstract

In situ HfB2–SiC–VSi2 composite was fabricated by reactive pressureless sintering at the temperature of 2150 °C for 4 h under a vacuum atmosphere. In situ SiC and VSi2 reinforcements were formed using VC and Si powders as starting materials according to the following reaction: VC + 3Si = SiC + VSi2. Microstructural studies and thermodynamic calculations revealed that in situ VSi2 and SiC phases were mostly formed and homogeneously distributed in HfB2 skeleton. The results showed that the density of in situ HfB2–SiC–VSi2 composite was 98%. Besides, the mechanical properties of the composite were effectively enhanced by the formation of in situ second phases. The Vickers hardness and the fracture toughness of the composite reached 20.1 GPa and 5.8 MPa m−1/2, respectively.

Highlights

Advanced ceramics and protective coatings for high temperature applications have been recently a ttracted[1,2,3,4,5,6,7,8,9,10,11]
It has been reported that the oxide impurities (HfO2, B2O3) of H fB2 starting powder can prevent the densification of HfB2 ceramic[21]
The very small amount of porosity is observed in the microstructure after the sintering process which confirms that the temperature of the sintering process (~ 2150 °C) was adequate to remove most of the porosities

Summary

Introduction

Advanced ceramics and protective coatings for high temperature applications have been recently a ttracted[1,2,3,4,5,6,7,8,9,10,11]. Because of the low self-diffusion coefficients and tightly covalent bonding, generally, pressure-assisted methods such as Spark plasma sintering (SPS), and Hot pressing (HP) are applied for consolidation of HfB2-based composites. Using these methods restrict geometrical dimensions, especially for complex-shaped specimens. Brochu et al.[18] densified Z rB2 ceramic by reactive pressureless sintering method using Zr and B powders as starting materials. They did not use any additive for the densification of Z rB2; the maximum density was reported about 79% for monolithic ZrB2. Silicides have been added to HfB2 to improve its mechanical properties owing to such superior properties as excellent creep resistance and oxidation behavior

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