Characterization of hot-pressed Ti3SiC2–SiC composites

https://doi.org/10.1016/j.ijrmhm.2020.105232Get rights and content

Highlights

  • Ti3SiC2-SiC composites were densified by hot pressing process at 1550 °C.

  • Uniform distribution of SiC in the Ti3SiC2 matrix led to an improved hardness.

  • Maximum value for flexural strength was obtained by adding 15 vol% SiC.

  • Fracture toughness of SiC-doped samples was lower than that of monolithic MAX phase.

Abstract

The high-density Ti3SiC2-SiC composites with different SiC volume contents were fabricated by hot pressing technique under 35 MPa in a vacuum atmosphere at 1550 °C for 30 min. Microstructural observation showed that the distribution of SiC particulates in the Ti3SiC2 matrix was uniform which improved the hardness of Ti3SiC2–20 vol% SiC sample (13.9 GPa), compared to monolithic Ti3SiC2 (7.1 GPa). The sample containing 15 vol% SiC showed the highest flexural strength value, compared to the other Ti3SiC2-SiC samples and the monolithic Ti3SiC2. The fracture toughness of the Ti3SiC2-SiC samples was also lower than that of the monolithic Ti3SiC2 MAX phase.

Introduction

Ceramics are materials with unique features including high-temperature resistance, high strength, and elastically stiffness, but they suffer from inherent brittleness, low machinability, and thermal shock resistance [1]. Therefore, to tackle these drawbacks, MAX phase ceramics (e.g., Ti2AlC, Ti2AlN, Ti3AlC2, and Ti3SiC2) with a hexagonal structure and combination of properties of both metals and ceramics have recently been produced [[2], [3], [4]]. These materials are a category of ceramics with a main formula of Mn+1AXn where M represents a transition metal, n = 1, 2 or 3, A is an element belongs to IIIA or IVA groups, and X nominates a nitrogen or carbon [5]. Titanium silicon carbide (Ti3SiC2) is a MAX phase compound with a layered structure and is an encouraging candidate for high-temperature applications [[1], [2], [3], [4], [5], [6]]. It has hexagonal crystal structure, lattice parameters of c = 1.7669 nm and a = 0.3068 nm [1]. In addition to ease of machinability, this material has excellent properties such as electrical [5,7] and thermal conductivity of 4.5 × 106 Ω_1 m_1 and 40 W/mK, respectively [7], proper thermal shock resistance, high Young's modulus (320 GPa), high toughness (6–11 MPa m1/2), moderate flexural strength (260–600 MPa), and low hardness (~4 GPa) [[5], [6], [7], [8]]. Therefore, Ti3SiC2 has great potential to be used in high-temperature applications (e.g., heating elements, metal smelting, and automobile engines) and is a suitable substitute for superalloys in many chemical and petrochemical applications [1,8,9].

In recent years, some efforts have been made to develop Ti3SiC2-based composite ceramics. In this regard, hard secondary phases (e.g., Al2O3 and TiC [1]) have been incorporated into the Ti3SiC2 matrix to improve the desired properties. It has been reported that the presence of SiC as a reinforcing phase improves the oxidation [[1], [2], [3], [4], [5]], thermal shock [1], and wear resistance [[5], [6], [7], [8], [9], [10]] of composites. However, a more in-depth understanding of the mechanisms by which a secondary phase performs in a MAX phase matrix is still missing.

Ti3SiC2-SiC composites have so far been produced by different methods such as hot-pressing (HP), hot isostatic pressing (HIP), and spark plasma sintering (SPS) [11].

Although many attempts have been made to synthesize Ti3SiC2–SiC composites by hot pressing or spark plasma sintering methods, further investigation is required to determine the suitable amount of SiC in which desirable mechanical properties is obtained.

In this research, Ti3SiC2-(10–25 vol%) SiC composites were manufactured by hot pressing process. The influences of SiC on the microstructure, physical, and mechanical behavior of the produced composites were investigated by different analytical techniques such as SEM, XRD, and three-point flexural strength tests and compared with the hot-pressed Ti3SiC2 monolithic sample.

Section snippets

Sample preparation

In this research, Ti3SiC2 (average particle size: ≤ 15 μm; Xi'AN BIOF BIO-TECH Co. Ltd.) and SiC (average particle size: ≤ 0.7 μm; Xi'AN BIOF BIO-TECH Co. Ltd.) powders were used to fabricate Ti3SiC2-SiC composites by hot-press sintering technique. To synthesize Ti3SiC2-SiC samples, at first different amounts of Ti3SiC2 and SiC powders (in vol%; see Table 1) were mixed in ethanol followed by sonication for 15 min. Afterward, the slurry was wet ball-milled for 70 min with a 250 rpm speed using

Results and discussion

The XRD spectra of monolithic Ti3SiC2 and Ti3SiC2–20 vol% SiC samples sintered at 1550 °C are shown in Fig. 1. According to Fig. 1 (a), just Ti3SiC2 and TiC phases were identified in the XRD pattern of the Ti3SiC2 sample, revealing the decomposition of Ti3SiC2 during the hot pressing due to the weak carburization resistance of Ti3SiC2 (see reaction 1) [12].Ti3SiC2+3x1C3TiCx+SiC

In contrast, Ti3SiC2, TiC, and SiC phases were observed for the produced Ti3SiC2–20 vol% SiC composite, further

Conclusions

Ti3SiC2-SiC composites were fabricated by hot pressing from initial powders of Ti3SiC2 and SiC. The Ti3SiC2-based composites with SiC addition of 10–25% in volume fraction were synthesized to obtain the highest relative density composite. The results show that the highest relative density was related to the Ti3SiC2–20 vol% SiC composite because, according to the diffraction pattern of this sample, due to the high temperature of the hot pressing, the TiC phase was formed by the decomposition of

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.

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