Synthesis and mechanical and elevated temperature tribological properties of a novel high-entropy (TiVNbMoW)C4.375 with carbon stoichiometry deviation
Synthesis and mechanical and elevated temperature tribological properties of a novel high-entropy (TiVNbMoW)C4.375 with carbon stoichiometry deviation
复制标题
具有碳化学计量偏差的新型高熵 (TiVNbMoW)C 4.375 的合成及其机械和高温摩擦学性能
DOI：
10.26599/jac.2023.9220679
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发表时间：
2023-02-01
影响因子：
16.9
通讯作者：
Zhang, Yongsheng
中科院分区：
文献类型：
--
作者：
Li, Jicheng;Zhou, Yanchun;Zhang, Yongsheng
高熵碳化物是一组新兴的陶瓷，由于它们显示出良好的稳定性、高硬度（H）、高强度和上级抗蠕变性的组合，其有希望用于高温应用。然而，由于高熔点和低晶格扩散系数，高熵碳化物通常难以固结到接近全密度。为了科普这一挑战，本文采用TiC、V8 C7、NbC、Mo 2C和WC等不同碳化学计量比的二元碳化物制备了致密高熵（TiVNbMoW）C-4.375，并研究了碳空位对缺碳高熵（TiVNbMoW）C-4.375形成能力和力学性能的影响。有趣的是，尽管起始二元碳化物具有不同的晶体结构和碳化学计量，但所制备的高熵材料显示出具有相对高密度（98.1%）的岩盐结构和良好的机械性能，硬度为19.4 +/- 0.4 GPa，断裂韧性（K-IC）为4.02 MPa中心点m（1/2）。更重要的是，高熵（TiVNbMoW）C4.375在室温（RT）和800 ℃下表现出低摩擦系数（COF）。随着温度的升高，磨损率逐渐增大，这是由于高温下形成的低硬度氧化膜加剧了磨损。在800 ℃下，由足够的V2 O 5和MoO 3的氧化产物形成的润滑膜有效地改善了高熵（TiVNbMoW）C-4.375的摩擦学行为。磨损机制主要为晶粒拔出和脆性断裂引起的磨粒磨损以及高温反应产生的氧化磨损。研究结果对高温条件下高熵陶瓷材料的制备具有指导和参考价值。
High-entropy carbides are a nascent group of ceramics that are promising for high-temperature applications due to the combination of good stability, high hardness (H), high strength, and superior creep resistance that they display. Due to high melting points and low lattice diffusion coefficients, however, the high-entropy carbides are usually difficult to consolidate to a nearly full density. To cope with this challenge, herein, binary carbides including TiC, V8C7, NbC, Mo2C, and WC with different carbon stoichiometry were used to prepare dense high-entropy (TiVNbMoW)C-4.375, and the influence of carbon vacancy on formation ability and mechanical properties of carbon-deficient high-entropy (TiVNbMoW)C-4.375 were investigated. Intriguingly, although the starting binary carbides have different crystal structures and carbon stoichiometry, the as-prepared high-entropy material showed a rock-salt structure with a relatively high density (98.1%) and good mechanical properties with hardness of 19.4 +/- 0.4 GPa and fracture toughness (K-IC) of 4.02 MPa center dot m(1/2). More importantly, the high-entropy (TiVNbMoW)C4.375 exhibited low coefficient of friction (COF) at room temperature (RT) and 800 degrees C. Wear rate (W) gradually increased with the temperature rising, which were attributed to the formation of low-hardness oxidation films at high temperatures to aggravate wear. At 800 degrees C, lubricating films formed from sufficient oxidation products of V2O5 and MoO3 effectively improved tribological behavior of the high-entropy (TiVNbMoW)C-4.375. Wear mechanisms were mainly abrasive wear resulting from grain pullout and brittle fracture as well as oxidation wear generated from high-temperature reactions. These results are useful as valuable guidance and reference to the synthesis of high-entropy ceramics (HECs) for sliding parts under high-temperature serving conditions.