Improving fracture toughness of B4C – SiC composites by TiB2 addition

doi:10.1016/j.ijrmhm.2022.105930

International Journal of Refractory Metals and Hard Materials

Volume 108, November 2022, 105930

$International Journal of Refractory Metals and Hard Materials$

https://doi.org/10.1016/j.ijrmhm.2022.105930 Get rights and content

Highlights

•
0–20 wt% TiB2 added to B4C-SiC composites and evaluated the microstructure, elastic and mechanical properties.
•
29.5 GPa hardness was obtained with the addition of 15 wt%TiB2.
•
The fracture toughness increased by 28% with the addition of 10 wt% TiB2 when compared samples without TiB2 addition.

Abstract

B₄C-SiC composites can be used in many areas due to their superior properties. However, in order to be used as a body armor material in areas requiring high performance, their fracture toughness needs a degree of improvement. In this study, 0–20 wt% TiB₂ was added to B₄C-SiC samples that were consolidated at 1950 °C by spark plasma sintering method. The contribution of TiB₂ to the microstructure, elastic and mechanical properties of B₄C-SiC composites were investigated. The highest hardness was measured to be 29.5 GPa with 15 wt%TiB₂ addition. The highest fracture toughness was 3.08 MPa.m^1/2 found at sample made with 10 wt% TiB₂. Addition of 10 wt% TiB₂ increased the fracture toughness by 28%, with only a 5% decrease in relative density. In addition, the fracture mode of B₄C-SiC-TiB₂ composites is intergranular due to the addition of TiB₂.

Introduction

Boron carbide (B₄C) is known for its significant material properties such as high hardness exceeding 30 GPa, a low theoretical density of 2.52 g/cm³, high melting point, good wear resistance, high elastic modulus, and good chemical inertness [[1], [2], [3], [4], [5], [6]].

Silicon carbide (SiC) has a low theoretical density (3.21 g/cm³), a high hardness, and a high elastic modulus [[7], [8], [9], [10]].

Therefore, B₄C-SiC ceramics have a wide range of uses. They can be used as lightweight armor ceramics, blasting nozzles, grinding wheels, and control rods in nuclear reactors [1,[11], [12], [13]]. In addition to these superior properties, the fracture toughness of B₄C-SiC composites is quite low. Due to its low fracture toughness, usage of these composites may be limited, thus there is a need for improvement in terms of toughness [6,11,14].

One of the most common methods to increase fracture toughness is the second phase addition [12,15]. However, due to the fact that thermal expansion of coefficients of B₄C and SiC are very similar, producing B₄C-SiC composites does not increase the fracture toughness of these composites [13,16,17]. Preparing composites of carbides and TiB₂ has been reported as a way of increasing fracture toughness. However, these reports were focused on SiC addition into B₄C-TiB₂ composites, and not on TiB₂ addition into the B₄C-SiC system [15,18].

In this study, 0–20 wt% TiB₂ was added into lightweight B₄C-SiC composites and sintered via the Spark plasma sintering (SPS) method in order to increase their fracture toughness. In addition to this, the effect of TiB₂ addition on the elastic and mechanical properties of B₄C-SiC composites was examined.

Section snippets

Experimental

Commercially available boron carbide (Purity 96.5 wt%, HD-20, H.C. Starck GmbH&Co., Germany, average grain size 0.5 μm), silicon carbide (Purity 98.3 wt%, UF-25, H.C. Starck GmbH&Co., Germany, average grain size 0.5 μm), and titanium diboride (Purity 99.9 wt%, H. C. Starck GmbH&Co., Germany, average grain size below 2.5–3.5 μm) were used as starting powders.

40–60 wt% B₄C- 40 wt% SiC and 0–20 wt% TiB₂ were ball milled with SiC ball with 150 g of 3 mm SiC ball milling media for 24 h in ethanol

Result and discussion

Fig. 1 shows FESEM images of ion milled B₄C-SiC-TiB₂ composites. In the microstructure images, the dark gray areas are B₄C particles, the larger bright light gray areas are TiB₂ particles, and the smaller light gray areas are SiC particles. A uniform distribution of the three phases was observed in all composites, no agglomeration was detected. It is important as the agglomerates could cause non-uniform mechanical properties which then affect the overall performance of composite materials. In

Conclusions

B₄C-SiC-TiB₂ composites were produced by SPS. Dense B₄C-SiC-TiB₂ composites were prepared by spark plasma sintering at 1950 °C for 5 min. The highest hardness was 29.5 GPa and found at sample made with 50 wt% B₄C- 40wt%SiC- 15 wt% TiB₂. The highest fracture toughness was 3.08 MPa·m^1/2 and obtained at 50 wt% B₄C- 40wt%SiC- 10 wt% TiB_2. With the addition of 10 wt.% TiB₂ to B₄C-SiC, the fracture toughness value of the composite increased by 28% with a slight decrease in its density. The fracture

Data availability

The raw/processed data required to reproduce these findings cannot be shared at this time due to technical or time limitations.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

Research was sponsored by the National Science Foundation I/UCRC Award No.1540027. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of the National Science Foundation or the U.S. Government. The U.S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation herein. Additional funding was provided by the

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Improving fracture toughness of B4C – SiC composites by TiB2 addition

Highlights

Abstract

Introduction

Section snippets

Experimental

Result and discussion

Conclusions

Data availability

Declaration of Competing Interest

Acknowledgement

Mater. Sci. Eng. A

J. Eur. Ceram. Soc.

Powder Technol.

Trans. Nonferrous Metals Soc. China

Ceram. Int.

J. Eur. Ceram. Soc.

J. Eur. Ceram. Soc.

Ceram. Int.

Ceram. Int.

J. Eur. Ceram. Soc.

Pressureless sintering of boron carbide

J. Am. Ceram. Soc.

Improving fracture toughness of B₄C – SiC composites by TiB₂ addition