Effects of TiC0.4 on microstructure and properties of WC composites

• Published in: Journal of alloys and compounds 2022-12, Vol.925, p.166588, Article 166588
• Main Authors: Zou, Qin, Jiao, Zijian, Li, Yanguo, He, Wenquan, Li, Shuang, Luo, Yongan
• Format: Article
• Language: English
• Subjects: Composite materials; Compressive strength; Diffusion; Diffusion rate; External pressure; Flexural strength; Fracture toughness; Grain size; Hardness; High temperature; Mechanical properties; Microstructure; Non-stoichiometric TiC0.4; Oxidation; Oxidation resistance; Plasma sintering; Properties; Solid solutions; Spark plasma sintering; Stoichiometry; Thermal conductivity; Thermal resistance; Titanium carbide; Tungsten carbide; WC-5 wt% TiC0.4 composites
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2022.166588

WC composites with 5 wt% TiC0.4 were fabricated by spark plasma sintering (SPS) at sintering temperature of 1400–1700 °C for 10 min under an external pressure of 50 MPa. It can be observed that the WC-5 wt% TiC0.4 composites mainly consisted of WC phase and non-stoichiometric (W1−x, Tix)Cn solid solution phase and the amount of WC dissolving in TiC0.4 increased with sintering temperature. The (W1−x, Tix)Cn solid solutions uniformly distributed around WC grains and formed a semi-coherency interface with WC, which restricted the growth of WC grains and enhanced mechanical properties of the WC-5 wt% TiC0.4 composites. The average grain size of WC (251.5 ± 201.6 nm) in WC-5 wt% TiC0.4 composite sintered at 1600 ℃ was considerably smaller compared to most of previously reported WC-based composites. The existence of high content of C vacancies in non-stoichiometric TiC0.4 raised remarkably the diffusion rate of W and Ti atoms in the sintering process of WC-5 wt% TiC0.4 composites in contrast with stoichiometric TiC. The WC-5 wt% TiC0.4 composite sintered at 1600 ℃ possessed the optimum properties, with the hardness of 21.9 GPa, fracture toughness of 7.6 MPa·m1/2, flexural strength of 612 MPa and compressive strength of 2.7 GPa. Moreover, it can be confirmed that the oxidation resistance of WC-5 wt% TiC0.4 composite at higher temperature outperformed that below 1218 ℃. In addition, the WC-5 wt% TiC0.4 composite sintered at 1600 ℃ showed higher high-temperature hardness, lower thermal conductivity and better resistance to oxidation than those of conventional WC-Co composites. •In this paper, non-stoichiometric TiC0.4 was used to strengthen and toughen WC cemented carbides.•The incorporation of TiC0.4 into WC composite was conducive to evidently lowering the sintering temperature for almost full densification.•The nonstoichiometric (W1−x, Tix)Cn solid solutions formed a semi-coherency interface with WC, thus enhancing mechanical properties of the WC-5 wt% TiC0.4 composites.•The WC-5 wt% TiC0.4 composites provided several advantages, such as higher high-temperature hardness, lower thermal conductivity and better resistance to oxidation.