ISSN   1004-0595

CN  62-1224/O4

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W基化合物添加对ZrB2-SiC陶瓷复合材料摩擦学性能的影响规律研究

Effect of W-Based Compounds on the Tribological Properties of ZrB2-SiC Ceramic Composites

  • 摘要: 采用放电等离子烧结技术制备了添加WC、WB和WSi2的ZrB2-SiC陶瓷复合材料,考察了W基化合物的添加对组织结构、力学性能和摩擦学性能的影响. 结果表明:WB和WSi2的添加原位形成了(Zr,W)B2固溶体相;WC的添加原位形成了(Zr,W)B2和(Zr,W)C固溶体相,固溶体相的形成获得了核壳结构,提高了致密度,抑制了ZrB2晶粒长大,提升了力学性能;添加WC后材料具有最高的硬度、屈服强度和断裂韧性. WC和WB的添加有效提高了摩擦系数稳定性和耐磨性;添加WC后,提升了强度和韧性,并形成了致密氧化铝和钨氧化物摩擦层,获得了最佳的摩擦学性能,磨损率相比ZrB2-SiC陶瓷降低了约50%;添加WB后,摩擦表面形成多裂纹的氧化铝摩擦层和大尺寸的氧化铝堆积;添加WSi2后,摩擦表面不能形成有效的氧化铝摩擦层,发生晶粒断裂和拔出,摩擦磨损严重.

     

    Abstract: ZrB2-SiC ceramics are a class of materials with potential employ in the aerospace sector, owing to their excellent thermo-physical properties and their high melting point. In this work, ZrB2-SiC ceramic composites were synthesized using the spark plasma sintering (SPS) technology, with a particular focus on the incorporation of various W-based compounds: tungsten carbide (WC), tungsten boride (WB) and tungsten silicide (WSi2). The impact of these W-based compound additives on the microstructural, mechanical and tribological properties of the ZrB2-SiC ceramic composites were systematically studied. The results revealed that the addition of WB and WSi2 facilitated the in-situ formation of a (Zr, W)B2 solid solution phase. In the case of WC addition, a more complex scenario unfolded, where both (Zr, W)B2 and (Zr, W)C solid solution phases were observed. These solid solution phases were instrumental in forming a unique core-shell structure, which significantly improved the material's density, grain size and mechanical properties. The WC-added ZrB2-SiC ceramic exhibited the highest relative density and the lowest average grain size. Detailed examinations of the mechanical properties of these composites indicated a marked enhancement in attributes such as hardness, yield strength and fracture toughness. The comparison of hardness, yield strength and fracture toughness of ceramic composites was WC-added ZrB2-SiC ceramic > WSi2-added ZrB2-SiC ceramic > WB-added ZrB2-SiC ceramic > ZrB2-SiC ceramic. This phenomenon was attributed to the core-shell structure that contributed to a refined grain size, higher density and greater uniformity in the microstructure. Compared with ZrB2-SiC ceramic, trans-granular crack propagation and crack branching were found in the crack propagation path of W-based compound added ceramics. The tribological properties were assessed through rigorous wear and friction tests. The addition of WC and WB substantially improved the stability of friction coefficient and the composite's wear resistance. The comparison of wear resistance of ceramic composites was WC-added ZrB2-SiC ceramic > WB-added ZrB2-SiC ceramic > WSi2-added ZrB2-SiC ceramic ≈ ZrB2-SiC ceramic. Compared to the ZrB2-SiC ceramics, the wear rate in the WC-added composites was significantly reduced, by approximately 50%. This improvement of WC-added composites was largely due to the formation of a dense, protective layer of alumina and tungsten oxide on the friction surface, as well as the enhanced mechanical properties. The worn surface of WB-added ZrB2-SiC ceramic exhibited a distinct multi-cracked alumina friction layer, accompanied by the accumulation of larger alumina particles. On the worn surface of WSi2-added ZrB2-SiC ceramic, the effective alumina friction layer was not formed, resulting in pronounced grain fracture and pull-out. This research not only demonstrated the potential of W-based compounds in enhancing the mechanical and tribological properties of ZrB2-SiC ceramic composites, but also provided a detailed explanation of the relative mechanisms.

     

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