ISSN   1004-0595

CN  62-1224/O4

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(TiZrNbMoTa)B2高熵陶瓷的制备与摩擦学性能研究

Preparation and Tribological Properties of (TiZrNbMoTa)B2 High Entropy Ceramics

  • 摘要: 通过高能球磨和放电等离子烧结(SPS)技术制备了(TiZrNbMoTa)B2高熵陶瓷,探讨了球磨条件对高熵陶瓷物相组成、微观结构和力学性能影响,着重研究了(TiZrNbMoTa)B2高熵陶瓷从25~800 ℃的摩擦学性能及磨损机制. 结果表明:随着球磨速度的提高,(TiZrNbMoTa)B2高熵陶瓷内各元素分布趋向均匀,(TiZrNbMoTa)B2逐渐形成单一均匀的具有六方最密堆积(HCP结构)的金属二硼化物固溶相;高熵陶瓷的硬度、断裂韧性和弯曲强度也随之提升. (TiZrNbMoTa)B2高熵陶瓷的高温耐磨性能较低温耐磨性能提高了36倍,其磨损机制由中低温的磨粒磨损转变为高温下的氧化磨损和磨粒磨损. B2O3的高温自润滑效应和磨损表面氧化釉质层的生成是高熵陶瓷具有良好高温耐磨性能的主要原因.

     

    Abstract:
    High-entropy diboride ceramics possess the advantages of refractory metal borides and high-entropy materials, with high hardness and good oxidation resistance, and are, therefore, expected to be applied in high-temperature wear-resistant fields. However, current research reports on high-entropy diboride ceramics mainly focus on synthesis, preparation, mechanical properties, and oxidation resistance, while tribological properties still need to be improved. In addition, high-entropy diboride ceramics still have problems, such as high synthesis temperature, poor density, element segregation, and poor fracture toughness. Therefore, it is necessary to improve the preparation process of high-entropy diboride ceramics and explore their tribological properties.
    This study selected (TiZrNbMoTa)B2 with high hardness as the basic component, and using five refractory transition metal element powders of Ta, Mo, Ti, Zr, Nb, and boron powder as raw materials, successfully prepared (TiZrNbMoTa)B2 high-entropy ceramics through high-energy ball milling and SPS in-situ reaction sintering. The improvement process aimed to reduce the reaction energy and the introduction of impurities. The influence of the preparation process of (TiZrNbMoTa)B2 high-entropy ceramics on its microstructure and mechanical properties was investigated. In order to further broaden the application of high-entropy diboride and provide technical and theoretical support for improving the tribological properties of high-entropy diboride, the tribological properties of (TiZrNbMoTa)B2 high-entropy ceramics from 25 ℃ to 800 ℃ were emphatically explored. The changes in the composition and structure of (TiZrNbMoTa)B2 high-entropy ceramics before and after friction were analyzed in detail using XPS, SEM, DSC-TG, and other characterization methods. The wear mechanism and wear resistance mechanism of (TiZrNbMoTa)B2 high-entropy ceramics were analyzed.
    The main results and conclusions were as follows: with the increase of milling speed, the distribution of elements in (TiZrNbMoTa)B2 high entropy diborides tended to be uniformly distributed, and (TiZrNbMoTa)B2 formed a single homogeneous solid solution phase of hexagonal metal diboride. Meanwhile, by virtue of the lattice distortion effect and solid solution strengthening effect inherent to high entropy materials, the mechanical properties of these ceramics were significantly enhanced with escalating milling speeds, as evidenced by an elevation in Vickers hardness from 23.42 to 28.18 GPa, an augmentation in fracture toughness from 2.13 MPa·m1/2 to 2.47 MPa·m1/2, and a reinforcement in bending strength from 83.33 MPa to 96.67 MPa. (TiZrNbMoTa)B2 high entropy diborides had good high-temperature wear resistance, and the average wear rate at 600 °C was 8.98×10−6 mm3/(N·m), which was 36 times higher than that at room temperature. The good high-temperature wear resistance was contributed by the high-temperature self-lubrication effects of B2O3 and the formation of a dense enamel layer on the surface of the sample, which was composed of metal oxides and (TiZrNbMoTa)B2 high entropy phase. The wear mechanism of (TiZrNbMoTa)B2, high entropy diborides, was abrasive wear at low and medium temperatures. At high temperatures, the main wear mechanism was abrasive wear and oxidation wear. As a result of high-temperature oxidation, the tribological properties of (TiZrNbMoTa)B2 high-entropy ceramics had seen a slight decline. Hence, bolstering the high-temperature oxidation resistance of (TiZrNbMoTa)B2 high-entropy ceramics would be a pivotal strategy to improve their high-temperature wear resistance.

     

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